Studies


 


 

 

 


What the science says about PowerCranks and other studies related to cycling and other athletic performance

On this page we will list (sometimes with a short discussion) a few selected articles or studies either about PowerCranks or those with particular relevance to PowerCranks. Just click on the study title and be taken to the abstract or discussion of it and a link to the actual study, if available.

PowerCranks studies:

1. Effects of short-term training using powercranks on cardiovascular fitness and cycling efficiency

This study demonstrates a 10% improvement in cycling efficiency after 6 weeks on PowerCranks.

Single leg cycle training is superior to double leg cycling in improving the oxidative potential and metabolic profile of trained skeletal muscle

CR Abbiss, et. al. - Edith Cowan University

ABSTRACT

Single leg cycling may enhance the peripheral adaptations of skeletal muscle to a greater magnitude than double leg cycling. The purpose of the current study was to determine the influence of 3 wk high-intensity single leg and double leg cycle training on markers of oxidative potential and muscle metabolism and exercise performance. In a crossover design, nine trained cyclists (78 ± 7 kg, VO(2max): 59 ± 5 ml(.)kg(-1.)min(-1)) performed an incremental cycling test and a 16 km cycling time trial before and after 3 wk of double leg and counterweighted single leg cycle training (2 training sessions per wk). Training involved either 3 (double) or 6 (single) maximal 4 min intervals with 6 min recovery. Mean power output during the single leg intervals (198 ± 29W) was more than half that of the double leg intervals (344 ± 38W; P<0.05). Skeletal muscle biopsy samples obtained from the vastus lateralis revealed a training-induced increase in phosphorylated AMPKα(T172) for both groups (P<0.05). However, there was a greater increase in cytochrome c oxidase subunits II (COX II) and IV (COX IV) and GLUT-4 protein concentration following single compared with double leg cycling (P<0.05). Training-induced improvements in VO(2max):(3.9 ± 6.2% vs 0.6 ± 3.6%) and time trial performance (1.3 ± 0.5% vs 2.3 ± 4.2%) were similar following both interventions. We conclude that short-term high-intensity single leg cycle training can elicit greater enhancement in the metabolic and oxidative potential of skeletal muscle compared with traditional double leg cycling. Single leg cycling may therefore provide a valuable training stimulus for trained and clinical populations.

Comment

This study looks at isolated leg pedaling in a different way than what most think of isolated leg pedaling in that the other pedal is counterbalanced. From Jim Martin, the senior author of the study: "By adding a counterweight to one crank, you can pedal with one leg but with biomechanics that are similar to those during normal double leg cycling. Much different than you would do during non-counterweighted single leg cycling." This is closer to what the condition PowerCranks puts on the athlete, in that all that is required when pedaling with two legs with PowerCranks is to fully unweight on the backstroke to keep the pedal going, similar to the requirements of this study.

The results really support the benefits of counterweighted isolated leg training. Not only were the athletes able to generate substantially more wattage one legged than would be expected taking half of the two legged interval power (25 watts - indicating, most likely, improved efficiency) but other metabolic changes indicated this to be a more effective way of training cycling musculature. Even though overall improvements were not seen in this study, as the senior author has stated about this study: "While it is true that we did not obtain a performance improvement we did not really expect it after only 6 total workouts over three weeks. Anytime you design a study you are constrained by what you believe the participants are will to do and how much time they will take off of their normal training. We decided on three weeks knowing it might not improve performance. That's where the analysis of muscle biopsies came in. We pulled biopsies before and after each block of training (single and double) and analyzed the tissue. The results for increases in glut-4 (insulin and contraction mediated glucose transporter) and CoxII and CoxIV (limiting steps in the respiratory chain) are highly compelling. They suggest that this will be a potent training stimulus as well as clinical modality. "

Link to study: PubMed

2. Physiological responses to training using PowerCranks on trained cyclists

This study demonstrates a 15% improvement in VO2max and an 11% increase in maximum power after 6 weeks of exclusive PowerCranks training.

Physiological responses to training using PowerCranks on trained cyclists.
Stephen J. Dixon, Michael F. Harrison, Kenneth A. Seaman, Stephen S. Cheung and J. Patrick Neary. University of New Brunswick, Fredericton, NB; Dalhousie University, Halifax, NS; University of Regina, Regina, SK

ABSTRACT

PowerCranks are cycling cranks that are independent of each other, requiring force application throughout the pedal stroke, theoretically increasing muscle recruitment and stimulus in the legs. This study examined the physiological adaptations to PowerCranks, and the time course of responses in maximal and submaximal cycling performance. Eight Trained cyclists (35.1 ± 6.8 yr) participated in 6 wks of 100% immersion training using solely PowerCranks, consisting of ~8 h/wk of aerobic and anaerobic (~80:20) cycling training. A continuous incremental cycling test to exhaustion (50 W increase every 2 min) was performed prior to and following the training program using normal cranks. In addition, 10 min of submaximal cycling (70% of VO2max wattage) were performed with both normal cranks and PowerCranks at an approximate cadence of 85 rpm, pre and post training. VO2max increased 15.6% (58.1 ± 5.8 to 67.3 ± 6.6, P=0.013). Maximum power increased 11.6% (316.7 ± 25.8 to 358.3 ± 20.4, P=0.011) following PowerCranks training. In summary, our data suggest that PowerCranks increased maximal aerobic capacity and power in trained cyclists. Supported by NSERC

Oral presentation at Canadian Society of Exercise Physiologists meeting, November 2006. unpublished.

COMMENT: We were again surprised that such a large improvement, especially in VO2 max, could be documented in such a short period of time. Although, again, in hindsight quite plausible as the new muscles should be starting to show substantial aerobic adaption within this period of time and most users are well past the coordination adaption period in this time. If you are using more muscle when you exercise your VO2 max should be higher. It is that simple. PowerCranks simply force the cyclist to use more muscles than they ordinarily do.

 

3. Training With Independent Cranks Alters Muscle Coordination Pattern in Cyclists

Looks at the changes that occur in muscle coordination with 18 hours of PowerCranks training and also what happens if one stops using PowerCranks.

Training With Independent Cranks Alters Muscle Coordination Pattern in Cyclists

UNIVERSITA’ DEGLI STUDI DI URBINO

Fernández-Peña, E, Lucertini, F, and Ditroilo, M.
J Strength Cond Res 23(6): 1764-1772, 2009

In cycling, a circular pedaling action makes the most useful contribution to forward propulsion. Training with independent cranks (IC) has been proposed to improve the pedaling action. The aims of this study were, first, to assess whether the intermuscular coordination pattern of the pedaling action with normal cranks (NC) is modified after a training period with IC and, second, to determine if the new coordination pattern is maintained after a washing-out period. Eighteen cyclists, divided into a control (CG) and an experimental (EG) group, underwent 2 test sessions (T1 and T2) separated by 2 weeks of training (18 hours). The electromyographic (EMG) activity of 4 lower limbs' muscles was recorded while the athletes pedaled at 80 rpm for 60 seconds at 30 and 50% of the maximal power output determined during a maximal pedaling test. The tasks were performed with IC (EG) and NC (EG and CG). The EG underwent a retention test session (T3) after another 18-hour training with NC. EG showed a significant (45.8 ± 8.8 vs. 36.0 ± 6.1%, p < 0.01 at 30% intensity) and a quasi-significant (62.7 ± 10.3 vs. 54.2 ± 8.7%, p = 0.09 at 50% intensity) decrease in vastus lateralis EMG activity and a quasi-significant (36.4 ± 13.4 vs. 43.5 ± 10.9%, p = 0.09 at 30% intensity) and a significant (54.5 ± 12.1 vs. 65.5 ± 16.1%, p < 0.05 at 50% intensity) increase in biceps femoris EMG activity between T1-NC and T2-NC. By T3, EMG activity returned to initial levels (T1). On the contrary, CG did not reveal any significant variation. The results provide scientific support for muscle coordination pattern alteration from the use of IC, potentially achieving a more effective pedaling action. IC training reduces quadriceps exertion, thus preserving it for important moments during competition.

Comment

This does not surprise us as the adaption period was short in this study so one would hardly expect the changes to be permanent. It remains to be seen if one trained for a very long time as to whether the changes can become "permanent" or how slowly they will revert. Find a preliminary slideshow of the study here.

4. PowerCranks versus normal bicycle cranks: An EMG comparison

Looks at muscle activation changes associated with PowerCranks use. Get's slightly different results than the study above.

PowerCranks versus Normal bicycle cranks: An EMG comparison

Nuckles, J., Bills, B., Wagner, D., and Bressel, E., HPER Department, Utah State University

ABSTRACT

Powercranks are an independent bicycle crank system that eliminates contralateral leg contribution during the pulling phase of the crank cycle. As such, Powercranks are thought to activate and thus train the hip and knee muscle flexors to a greater extent then pedalling with normal cranks. Our study examined if the hip and knee flexors were in fact more active during pedalling with Powercranks than normal cranks. Eight participants randomly performed 5 min exercise bouts using Powercranks and normal cranks while surface EMG activity of muscles iliopsoas, rectus femoris, biceps femoris, and lateral gastrocnemius were recorded during stationary ergometry. EMG data were collected 1 week after cessation of a 6 week Powercrank training program. Raw EMG data for each muscle were analyzed by first computing the average root mean square (RMS) for ten crank cycles and then normalizing the mean RMS value to the peak RMS value for each muscle. Results revealed that muscles iliopsoas and rectus femoris were 31% and 35% more activity, respectively, during the Powercrank than normal crank condition (p = 0.001-0.017). Muscles biceps femoris and lateral gastrocnemius were not different between conditions (p > 0.05). From these results it may be concluded that after familiarization, pedalling with Powercranks requires greater muscle activation from hip flexor but not knee flexor muscles suggesting that pedalling with Powercranks may be a more effective exercise for the hip flexor muscles than pedalling with normal cranks.

Oral presentation at Southwest regional meeting of the American College of Sports Medicine (SWACSM) in San Diego, CA on Nov. 9, 2007. unpublished.

COMMENT: While we are not surprised by the large improvement seen in the ilipsoas muscles we are a little surprised at the lack of change seen in the hamstring and "increase" seen in the quad (rectus femoris) muscles (we would "expect" to see an increase in hamstring activation and a lessening of the quads (unless the power is substantially increased) of the quads. This "unexpected result" may be from the study design in that the data was collected one week after only a six week period PowerCranks training or that the rectus femorus was seen to be increased because timing is substantially different, which we would expect. The devil is in the details, which we don't have.

5. Does training with PowerCranks affect economy of motion, cycling efficiency, oxygen uptake and muscle activation patterns in trained cyclists?

Does training with PowerCranks™ affect economy of motion, cycling efficiency, oxygen uptake and muscle activation patterns in trained cyclists?

Masters Thesis - Jack Burns
Edith Cowen University

Abstract

PowerCranks™ are claimed to increase economy of motion and cycling efficiency by reducing the muscular recruitment patterns that contribute to the resistive forces occurring during the recovery phase of the pedal stroke. However, scientific research examining the efficacy of training with PowerCranks™ is lacking. Therefore, the purpose of this study was to determine if five weeks of training with PowerCranks™ improves economy of motion (EOM), gross efficiency (GE), oxygen uptake (Error! Bookmark not defined.V.O2) and muscle activation patterns in trained cyclists. Sixteen trained cyclists were matched and paired into either a PowerCranks™ (PC) or Normal Cranks (NC) training group. Prior to training, all subjects completed a graded exercise test (GXT) using normal bicycle cranks. Additionally, on a separate day the PC group performed a modified GXT using PowerCranks™ and cycled only until the end of the 200W stage (PCT). During the GXT and PCT, FeO2, FeCO2 and V.E were measured to determine EOM, GE and V.O2max. Integrated electromyography (iEMG) was also used to examine selected muscular activation patterns. Subjects then repeated the tests following the completion of training on their assigned cranks. No significant improvements were observed for EOM, GE, V.O2max or iEMG in either the PC or NC group when subjects were cycling with normal cranks during the GXT. Likewise, no significant training effects were observed when PC subjects cycled with PowerCranks™ during the PCT. PC group subjects were significantly less efficient and economical, before and after training when cycling with PowerCranks™ compared to cycling with normal cranks. The results from this study do not support benefits claimed by PowerCranks™, however further research is needed to examine the influence of training with PowerCranks™ on various physiological variables over a more prolonged training duration.

Comments

This is really an interesting study. It demonstrates the difficulties that users experience when they first get on the cranks and it demonstrates the improvements that people see in the first weeks as they adapt. The only problem is the study didn't quite last long enough (5 weeks) to demonstrate statistical significance in the changes that were seen but that surely were coming. The changes seen were best demonstrated in table 7, which is reproduced below. The NC(NC) group were the normal crank controls testing on normal cranks. The PC(NC) group was the PowerCranks group testing on normal cranks and the PC(PC) group is the PC group testing on PC's. Note the big drop in efficiency when riding on PC's but as one adapts and improves this is transferred to the testing on normal cranks also.

 

Does training with PowerCranks™ affect economy of motion, cycling efficiency, oxygen uptake and muscle activation patterns in trained cyclists?

Masters Thesis - Jack Burns
Edith Cowen University

Abstract

PowerCranks™ are claimed to increase economy of motion and cycling efficiency by reducing the muscular recruitment patterns that contribute to the resistive forces occurring during the recovery phase of the pedal stroke. However, scientific research examining the efficacy of training with PowerCranks™ is lacking. Therefore, the purpose of this study was to determine if five weeks of training with PowerCranks™ improves economy of motion (EOM), gross efficiency (GE), oxygen uptake (Error! Bookmark not defined.V.O2) and muscle activation patterns in trained cyclists. Sixteen trained cyclists were matched and paired into either a PowerCranks™ (PC) or Normal Cranks (NC) training group. Prior to training, all subjects completed a graded exercise test (GXT) using normal bicycle cranks. Additionally, on a separate day the PC group performed a modified GXT using PowerCranks™ and cycled only until the end of the 200W stage (PCT). During the GXT and PCT, FeO2, FeCO2 and V.E were measured to determine EOM, GE and V.O2max. Integrated electromyography (iEMG) was also used to examine selected muscular activation patterns. Subjects then repeated the tests following the completion of training on their assigned cranks. No significant improvements were observed for EOM, GE, V.O2max or iEMG in either the PC or NC group when subjects were cycling with normal cranks during the GXT. Likewise, no significant training effects were observed when PC subjects cycled with PowerCranks™ during the PCT. PC group subjects were significantly less efficient and economical, before and after training when cycling with PowerCranks™ compared to cycling with normal cranks. The results from this study do not support benefits claimed by PowerCranks™, however further research is needed to examine the influence of training with PowerCranks™ on various physiological variables over a more prolonged training duration.

Comments

This is really an interesting study. It demonstrates the difficulties that users experience when they first get on the cranks and it demonstrates the improvements that people see in the first weeks as they adapt. The only problem is the study didn't quite last long enough (5 weeks) to demonstrate statistical significance in the changes that were seen but that surely were coming. The changes seen were best demonstrated in table 7, which is reproduced below. The NC(NC) group were the normal crank controls testing on normal cranks. The PC(NC) group was the PowerCranks group testing on normal cranks and the PC(PC) group is the PC group testing on PC's. Note the big drop in efficiency when riding on PC's but as one adapts and improves this is transferred to the testing on normal cranks also.

 

Other related studies or articles:

Cycling

1. Improved muscular efficiency displayed as Tour de France champion matures

The Lance Armstrong study (more correctly, a case report) looking at his progression between winning the world championships and winning his first Tour de France. It is especially interesting when combined with the recent newsletter report coming from Carmichael Training Systems that goes into the training emphasis of Lance during this period in which he was trying to develop a pedaling technique as forced by PowerCranks. (see below)

Improved muscular efficiency displayed as Tour de France champion matures

Edward F. Coyle

ABSTRACT

This case describes the physiological maturation from ages 21 to 28 yr of the bicyclist who has now become the six-time consecutive Grand Champion of the Tour de France, at ages 27–32 yr. Maximal oxygen uptake (O2 max) in the trained state remained at ~6 l/min, lean body weight remained at ~70 kg, and maximal heart rate declined from 207 to 200 beats/min. Blood lactate threshold was typical of competitive cyclists in that it occurred at 76–85% O2 max, yet maximal blood lactate concentration was remarkably low in the trained state. It appears that an 8% improvement in muscular efficiency and thus power production when cycling at a given oxygen uptake (O2) is the characteristic that improved most as this athlete matured from ages 21 to 28 yr. It is noteworthy that at age 25 yr, this champion developed advanced cancer, requiring surgeries and chemotherapy. During the months leading up to each of his Tour de France victories, he reduced body weight and body fat by 4–7 kg (i.e., ~7%). Therefore, over the 7-yr period, an improvement in muscular efficiency and reduced body fat contributed equally to a remarkable 18% improvement in his steady-state power per kilogram body weight when cycling at a given O2 (e.g., 5 l/min). It is hypothesized that the improved muscular efficiency probably reflects changes in muscle myosin type stimulated from years of training intensely for 3–6 h on most days.

The entire manuscript can be viewed and dowloaded here: J Appl Physiol 98: 2191-2196, 2005. First published March 17, 2005; doi:10.1152/japplphysiol.00216.2005

COMMENT: This study looks at Tour de France Lance Armstong and physiolgic changes that occurred over the years leading to his first TDF win. This is a most interesting article looking at the physiologic changes that occurred to Lance Armstrong over a seven year period, to the point of becoming the dominant cyclist in the world. The most interesting finding is the only substantial change is he improved his cycling efficiency of just under 10%. When combined with his reduced body weight this resulted in an 18% improvement in steady state power per kilogram body weight. We believe that change alone, when applied to someone who is already at world class level, can explain his dominance in the Tour de France that occurred at the end of this period without the need to invoke any performance enhancing drug use (drugs cannot cause such changes). Unfortunately, despite Coyle recognizing this huge finding Coyle only has a mediocre analysis as to how one might improved pedaling efficiency so substantially. Coyle simply assumes this improvement came about because Lance somehow changed his muscle fibre type to more slow twitch muscles without any discussion as to other potential methods (see the Luttrell study above). Regardless of how Lance managed to improve his efficiency, it is important to understand that improving cycling efficiency can improve performance IN EVERYONE! As clearly demonstrated in the Luttrell study above, PowerCranks can improve cycling efficiency in trained cyclists.

2. Biomechanical Evaluation of Pedaling Mechanics: (Bonus Lance Training Retrospective) by Carmichael Training Systems

This is an article from the CTS Newsletter that discusses pedaling mechanics in general and specifically, the pedaling mechanics of Lance Armstrong. It goes back to a pedal force analysis done by Lance in 1993 and notes: "But despite Lance’s symmetrical pedal stroke, there were areas where he could improve. The scientists noted that at the top and bottom of the pedal stroke, Lance contributed very little force to the pedals. By increasing his push over the top and his pull back through the bottom, they reasoned, Lance could deliver more power with each pedal stroke. Increasing energy delivery to the pedals at both of these phases in the stroke could result in a few more watts of power. Even though the changes would only result in a handful of additional watts with each revolution, Chris and Lance knew those increases could add up to significant performance gains during the course of a long training ride or race." The article explains that this has been a focus of Lance for the subsequent 17 years and that this change is what allows Lance to ride at such high cadences compared to everyone else. This can also explain the efficiency improvement documented by Coyle between 1993 and 2000 in the above "study". We don't know if Lance ever incorporated PowerCranks into his training to help him with this transformation but we do know that what is described is exactly what PowerCranks force the user to learn.

As Greg LeMond actually said, "I spent years learning how to pedal in this way, now people can learn it in months."

 

3. Pedaling Technique and Energy Cost in Cycling.

An interesting study that is the first that we know of that actually shows that pedaling technique really matters regarding cycling efficiency, with a chance of being wrong less than 1 in 1000. PowerCranks does for you what this study demands to improve cycling efficiency. No wonder Luttrell (see above) showed this change.

 

Pedaling Technique and Energy Cost in Cycling

Stig Leirdal and Gertjan Ettema

ABSTRACT

Pedaling Technique and Energy Cost in Cycling. Med. Sci. Sports Exerc., Vol. 43, No. 4, pp. 701–705, 2011. Purpose: Because cycling is an extreme endurance sport, energy saving and therefore efficiency is of importance for performance. It is generally believed that gross efficiency (GE) is affected by pedaling technique. A measurement of pedaling technique has traditionally been done using force effectiveness ratio (FE; ratio of effective force and total force). The aim of the present study was to investigate the relationship among GE, FE, and a new technique parameter, dead center (DC) size in competitive cyclists. Method: Twenty-one competitive cyclists cycled for 10 min at approximately 80% V˙ O2max at a freely chosen cadence (FCC). GE, FE ratio, and DC size were calculated from oxygen consumption and propulsive force recordings. Results: Mean work rate was 279 W, mean FCC was 93.1 rpm, and mean GE was 21.7%. FE was 0.47 and 0.79 after correction for inertial forces; DC was 27.3% and 25.7%,
respectively. DC size correlated better with GE (r = 0.75) than with the FE ratio (r = 0.50). Multiple regressions revealed that DC size was the only significant (P = 0.001) predictor for GE. Interestingly, DC size and FE ratio did not correlate with each other. Conclusions: DC size is a pedaling technique parameter that is closely related to energy consumption. To generate power evenly around the whole pedal, revolution may be an important energy-saving trait.

Med. Sci. Sports Exerc., Vol. 43, No. 4, pp. 701–705, 2011

COMMENT: A great study in experienced competitive cyclists to counter the "pedaling technique doesn't matter, just push harder" crowd. Leirdal and Ettema looked at a different metric, the "dead center" force, the minimal net force of the two cranks together usually seen when the cranks are perpendicular to the ground or at Top and/or Bottom "dead center". Using this metric they were able to correlate cycling efficiency to how small or large the force was here — with a chance of this study being wrong of less than 1 in 1,000. This is the first study that I know of that shows that a metric such as the CompuTrainer SpinScan has some real utility because SpinScan actually measures this DC torque. Of course, this also supports the PowerCranks as a training tool because the one thing we have been definitely been shown to improve is the torque across the top and bottom of the stroke (see below). PowerCrankers typically see an improvement in the "SpinScan" number of about 10 points.

Despite what the "just push harder" crowd says, pedaling technique matters. We disagree somewhat with their analysis of why this change occurs but the fact remains, it does occur.

4. Single leg cycle training is superior to double leg cycling in improving the oxidative potential and metabolic profile of trained skeletal muscle.

An interesting study that compares counterweighted isolated leg training (resembles PowerCranks requirements) to standard training. The study demonstrated a clear benefit to the single legged training in only 6 sessions.

Single leg cycle training is superior to double leg cycling in improving the oxidative potential and metabolic profile of trained skeletal muscle

CR Abbiss, et. al. - Edith Cowan University

ABSTRACT

Single leg cycling may enhance the peripheral adaptations of skeletal muscle to a greater magnitude than double leg cycling. The purpose of the current study was to determine the influence of 3 wk high-intensity single leg and double leg cycle training on markers of oxidative potential and muscle metabolism and exercise performance. In a crossover design, nine trained cyclists (78 ± 7 kg, VO(2max): 59 ± 5 ml(.)kg(-1.)min(-1)) performed an incremental cycling test and a 16 km cycling time trial before and after 3 wk of double leg and counterweighted single leg cycle training (2 training sessions per wk). Training involved either 3 (double) or 6 (single) maximal 4 min intervals with 6 min recovery. Mean power output during the single leg intervals (198 ± 29W) was more than half that of the double leg intervals (344 ± 38W; P<0.05). Skeletal muscle biopsy samples obtained from the vastus lateralis revealed a training-induced increase in phosphorylated AMPKα(T172) for both groups (P<0.05). However, there was a greater increase in cytochrome c oxidase subunits II (COX II) and IV (COX IV) and GLUT-4 protein concentration following single compared with double leg cycling (P<0.05). Training-induced improvements in VO(2max):(3.9 ± 6.2% vs 0.6 ± 3.6%) and time trial performance (1.3 ± 0.5% vs 2.3 ± 4.2%) were similar following both interventions. We conclude that short-term high-intensity single leg cycle training can elicit greater enhancement in the metabolic and oxidative potential of skeletal muscle compared with traditional double leg cycling. Single leg cycling may therefore provide a valuable training stimulus for trained and clinical populations.

Comment

This study looks at isolated leg pedaling in a different way than what most think of isolated leg pedaling in that the other pedal is counterbalanced. From Jim Martin, the senior author of the study: "By adding a counterweight to one crank, you can pedal with one leg but with biomechanics that are similar to those during normal double leg cycling. Much different than you would do during non-counterweighted single leg cycling." This is closer to what the condition PowerCranks puts on the athlete, in that all that is required when pedaling with two legs with PowerCranks is to fully unweight on the backstroke to keep the pedal going, similar to the requirements of this study.

The results really support the benefits of counterweighted isolated leg training. Not only were the athletes able to generate substantially more wattage one legged than would be expected taking half of the two legged interval power (25 watts - indicating, most likely, improved efficiency) but other metabolic changes indicated this to be a more effective way of training cycling musculature. Even though overall improvements were not seen in this study, as the senior author has stated about this study: "While it is true that we did not obtain a performance improvement we did not really expect it after only 6 total workouts over three weeks. Anytime you design a study you are constrained by what you believe the participants are will to do and how much time they will take off of their normal training. We decided on three weeks knowing it might not improve performance. That's where the analysis of muscle biopsies came in. We pulled biopsies before and after each block of training (single and double) and analyzed the tissue. The results for increases in glut-4 (insulin and contraction mediated glucose transporter) and CoxII and CoxIV (limiting steps in the respiratory chain) are highly compelling. They suggest that this will be a potent training stimulus as well as clinical modality. "

Link to study: PubMed
5. Physiological and biomechanical factors associated with elite endurance cycling performance

The most commonly cited study that supposedly "proves" that "just pushing harder" is the way to go and that learning to pedal in the PowerCranks fashion is counter productive. Find out what the study really says and how the study is misrepresented or misunderstood by the "naysayers".

Physiological and biomechanical factors associated with elite endurance cycling performance

E. F. Coyle, M, E. Feltner, S, A. Kautz, M. T. Hamilton, S. J. Montain, A. M. Baylor, L. D. Abraham, and G. W. Petrek

ABSTRACT

In this study we evaluated the physiological and biomechanical responses of "elite-national class" (i.e., group I; N = 9) and "good-state class" (i.e., group 2; N = 6) cyclists while they simulated a 40 km time-trial in the laboratory by cycling on an ergometer for I h at their highest power output. Actual road racing 40 km time-trial performance was highly correlated with average absolute power during the I h laboratory performance test (r = -0.88; P < 0.001). In turn, I h power output was related to each cyclists' V02 at the blood lactate threshold (r = 0.93; P < 0.00 I). Group I was not different from group 2 regarding V02max(approximately 70 ml.kg-I.min-I and 5.01 I.min-I) or lean body weight. However, group I bicycled 40 km on the road 10% faster than group 2 (P < 0.05; 54 vs 60 min). Additionally, group I was able to generate II % more power during the I h performance test than group 2 (P< 0.05), and they averaged 90 :i: 1% V02maxcompared with 86 :i: 2% V02ma>in group 2 (P = 0.06). The higher performance power output of group I was produced primarily by generating higher peak torques about the center of the crank by applying larger vertical forces to the crank arm during the cycling downstroke. Compared with group 2, group I also produced higher p.eak torques and vertical forces during the downstroke even when cycling at the same absolute work rate as group 2. Factors possibly contributing to the ability of group I to produce higher "downstroke power" are a greater percentage of Type I muscle fibers (P < 0.05) and a 23% greater (P < 0.05) muscle capillary density compared with group 2. We have also observed a strong relationship between years of endurance training and percent Type I muscle fibers (r = 0.75; P < 0.001). It appears that "elitenational class" cyclists have the ability to generate higher "downstroke power", possibly as a result of muscular adaptations stimulated by more years of endurance training.

The entire manuscript can be downloaded here: http://www.edb.utexas.edu/coyle/publications.php. Choose article #40

COMMENT: This study is frequently referenced by PC naysayers as having "proved" that "just pushing harder" is better than trying to pedal in circles. It does no such thing. There are only really three things that can be taken from this study.

1. The faster cyclists put out more power than the lesser cyclists.

2. The faster cyclists had better aerodynamics/bike handling skills than the lesser cyclists.

3. The faster cyclists had much better aerobic backgrounds than the lesser cyclists.

But, to go into more specifics:

First, Yes, there was a difference between how the two groups pedaled, with the faster group "pushing harder", and the lesser group "pulling up" more, but the pulling up difference did not reach statical significance. And, this difference was only present when riding at their maximum sustainable power. There was no difference in technique when riding at lower power. From page 101. Interestingly, the general pedaling technique of the cyclists in each group remained the same when the subject were all compared at the same power output (162 W for SLP) and at a cadence of 90 rpm (Fig. 7 and Table 7)." Even the "pushing harder" conclusion is slightly suspect since the authors (and all those who refer to this study to "prove" their point) fail to take into account the fact that downward forces during the pushing phase are a combination of both how hard the cyclists pushes and how heavy the leg is. Table 2 on page 97 shows the elite group had substantially more massive legs than the lesser group. Yet no attempt was made to account for this when analyzing how hard they were actually "pushing" - they simply assumed downward pedal force was equivalent to pushing. Further, no mention was made that this group also had to do more work on the backstroke to put more potential energy into the leg to simply unweight and raise it up to TDC. While it is probable that this group did push somewhat harder because they had more muscle mass to do so, it is also true they had to work harder on the backstroke (they essentially completely unweighted on the backstroke) such that the extra power they generated was probably balanced between both the "pushing" and "pulling" phase. This is what PowerCranks does, better balances these two phases of the bicycle stroke (and the top and the bottom also) such that these results actually support the PowerCranks position.

Second, there was a rational explanation to explain the "pulling up" difference. From page 105. "Data from our laboratory (Kautz et aI., submitted for publication) indicate that the torque production patterns exhibited by a cyclist were similar with increasing work rates, with the major difference at higher power outputs being increased peak torque during the downstroke and, to a much lesser extent, reduced negative torque during the upstroke." So, the Kautz data, shows that the closer one is to their maximum, the more they pull up on the backstroke. Even the elites do this. It is reasonable to conclude that the group 2 people were trying harder than the group 1 people since their pedaling patterns were essentially identical at lower power. It suggests that the differences that many think are so remarkable are not differences at all.

Third, the author writes this: "it is not surprising that a measure of effectiveness based solely on the orientation of the applied force fails to yield a meaningful measure of the true "effectiveness" of the movement. It is clear that any future research attempting to quantify effectiveness must consider more than the orientation of the applied pedal forces. This finding makes it unclear whether feedback devices that allow a cyclist to improve pedaling effectiveness (2,3,21) will lead to improved performance." According to the author, nothing can be concluded from this result as to whether feedback devices (such as PowerCranks), designed to improve pedaling effectiveness, will or will not lead to improved performance.

Fourth, the results of this study with regard to pedal forces goes against pretty much every study ever done before. From page 105. "Differences between the power output and pedaling cadence utilized in the present investigation and those used in previous studies (10,11,16,18,19,21,27) made it difficult to compare the present data with previous biomechanical data. This is especially so since none of the previous studies characterized competitive cyclists under conditions similar to those of the 1 h performance ride. A consistent conclusion of the previous studies was that cyclists did not pull up on the pedal during the upstroke. However, the present study found less negative torque during the upstroke than the previous studies. In some instances this reduction in negative torque was produced by pulling up on the pedal." It would mean more if one of the groups were shown to actually pedal as almost every study done to date has shown most cyclist pedal.

Fifth, only one side was analyzed for pedal forces. this presents the possibility if a rider has a right/left difference that the recorded data is not representative of what is actually going on.

Sixth, we don't know what the participants were told. If they were told the study would be looking at pedaling technique maybe the second group were more motivated to pedal as they thought the better athletes would pedal so they wouldn't look so bad, so they tried harder to "pull up" when the better people just rode as they normally do.

Seventh, as noted above, the elite group had substantially larger leg muscles with significantly more aerobic capacity than the lesser group. Is it surprising that they might have been able to "push harder" than the lesser cyclists?

 

6. The influence of pedaling rate on bilateral asymmetry in cycling

Many "naysayers" say that pedaling style doesn't matter, that the most important thing is to "just push harder". This one study puts such arguments to rest and proves as best as could ever be proved that pedaling style does matter for the purpose of pedaling power. In fact, in its comparisons between right and left legs it actually found that less powerful leg actually pushed harder but lost this advantage because of increased amount of negative force on the upstroke. So much for "just push harder". Replace that old, wrong, mantra with "just unweight, baby". Many thanks to Dr. A. Coggan for pointing us towards this study.

The influence of pedaling rate on bilateral asymmetry in cycling

Smak W, Neptune RR, Hull ML, Biomedical Engineering Department, UC Davis

ABSTRACT

The objectives of this study were to (1) determine whether bilateral asymmetry in cycling changed systematically with pedaling rate, (2) determine whether the dominant leg as identified by kicking contributed more to average power over a crank cycle than the other leg, and (3) determine whether the dominant leg asymmetry changed systematically with pedaling rate. To achieve these objectives, data were collected from 11 subjects who pedaled at five different pedaling rates ranging from 60 to 120 rpm at a constant workrate of 260 W. Bilateral pedal dynamometers measured two orthogonal force components in the plane of the bicycle. From these measurements, asymmetry was quantified by three dependent variables, the percent differences in average positive power (%AP), average negative power (%AN), and average crank power (%AC). Differences were taken for two cases--with respect to the leg generating the greater total average for each power quantity at 60 rpm disregarding the measure of dominance, and with respect to the dominant leg as determined by kicking. Simple linear regression analyses were performed on these quantities both for the subject sample and for individual subjects. For the subject sample, only the percent difference in average negative power exhibited a significant linear relationship with pedaling rate; as pedaling rate increased, the asymmetry decreased. Although the kicking dominant leg contributed significantly greater average crank power than the non-dominant leg for the subject sample, the non-dominant leg contributed significantly greater average positive power and average negative power than the dominant leg. However, no significant linear relationships for any of these three quantities with pedaling rate were evident for the subject sample because of high variability in asymmetry among the subjects. For example, significant linear relationships existed between pedaling rates and percent difference in total average power per leg for only four of the 11 subjects and the nature of these relationships was different (e.g. positive versus negative slopes). It was concluded that pedaling asymmetry is highly variable among subjects and that individual subjects may exhibit different systematic changes in asymmetry with pedaling rate depending on the quantity of interest.

J Biomech. 1999 Sep;32(9):899-906

COMMENT: While this study was not designed to look at pedaling style it is hard to imagine a better study to actually answer the basic question, does "style" matter? It is hard to imagine a study with better controls since we are comparing the right and left leg. The sex, age, athletic history, and essentially every other metric must be essentially identical between these two groups. What this study found was that the less powerful leg, compared to the other, in this group actually pushed harder than the more powerful leg but was made less powerful overall because of the increased negative forces on the back stroke. To those who say pedaling style is unimportant so "just push harder," we say, poke this study in your eye and see if it hurts.

Many thanks to Dr. Andrew Coggan for pointing us towards this study.

 

7. Cadence, efficiency, and performance in elite cyclists.

This study looked at optimal cadence in cycling and how it might affect performance since many studies have shown that cyclists tend to freely choose cadences that are above their most efficient cadence. The conclusion: "This study demonstrated that elite cyclists perform best at their most efficient cadence despite the maximal energy turnover rate being larger at a higher cadence." Efficiency is king when it comes to time-trial type efforts. Shows why the efficiency improvements achieved by Armstrong could make him the dominant cyclist of his era and why the efficiency improvements achieved by using PowerCranks, as demonstrated by Luttrell, are so important in explaining, in part, the improvements reported by most users.

Cadence and performance in elite cyclists.

Foss Ø, Hallén J.

ABSTRACT

Many studies have attempted to describe the optimal cadence in cycling. However, the effect on performance has received little attention. The aim of the present study was therefore to examine the effect of cadence on performance during prolonged cycling (approximately 30 min). Fourteen male elite cyclists performed two or five time trials at different cadences [60, 80, 100, 120 rpm or freely chosen cadence (FCC)]. The total work was the same between the time trials, and the subjects were instructed to complete each time trial as fast as possible by adjusting the workload with buttons mounted on the handlebar. Accumulated work and cadence was visualised on a monitor. Oxygen uptake was measured continuously and blood lactate concentration every fifth minute. Compared to 80 rpm, finishing times at 60, 100 and 120 rpm were 3.5, 1.7 and 10.2% slower (P<0.05). Finishing time at FCC (mean 90 rpm) was indistinguishable from 80 and 100 rpm. Gross efficiency at 80 rpm was 2.9, 2.3, 3.4 and 12.3% larger than at 60, FCC, 100 and 120 rpm, respectively (P<0.05). The maximal energy turnover rate was 1.7% higher at 100 than at 80 rpm (P<0.05). This could not, however, compensate for the 3.4% lower efficiency at 100 rpm. This study demonstrated that elite cyclists perform best at their most efficient cadence despite the maximal energy turnover rate being larger at a higher cadence.

COMMENT: Many have argued for years that the fact that cyclists tend to race at cadences above cadences shown to be most efficient by studies "proves" that effiency is not important to racing performance. This study proves that cycling efficiency is important to performance, at least for time-trial type efforts.

So, why do cyclists tend to ride at higher cadences than are most efficient? It is probably because higher cadences, while a little less efficient, allow the cyclist to more quickly respond to surges by opponents in races that are much more tactical. That doesn't mean that higher cadences are optimum for time trial performances as demonstrated by this study.

This study also helps explain why that 8% improvement in cycling efficiency measured by Dr. Coyle in Lance Armstrong (Improved muscular efficiency displayed as Tour de France champion matures.) after he was World Champion helped transform him into the dominant cyclist of his era and, in view of the Luttrell study (Effects of short-term training using powercranks on cardiovascular fitness and cycling efficiency.), which showed an overall 10% improvement in cycling efficiency from training with PowerCranks compared to controls, helps explain, in part, the huge performance improvements reported by PowerCrankers.

Link to study: PubMed

Running

1. Factors affecting running economy in trained distance runners.

A study that looks at the different factors that affect running economy. While PowerCranks are not specifically mentioned you will find that many of the factors mentioned are directly influenced by PowerCranks training.

Factors affecting running economy in trained distance runners

Saunders PU, Pyne DB, Telford RD, Hawley JA.

ABSTRACT

Running economy (RE) is typically defined as the energy demand for a given velocity of submaximal running, and is determined by measuring the steady-state consumption of oxygen (VO2) and the respiratory exchange ratio. Taking body mass (BM) into consideration, runners with good RE use less energy and therefore less oxygen than runners with poor RE at the same velocity. There is a strong association between RE and distance running performance, with RE being a better predictor of performance than maximal oxygen uptake (VO2max) in elite runners who have a similar VO2max). RE is traditionally measured by running on a treadmill in standard laboratory conditions, and, although this is not the same as overground running, it gives a good indication of how economical a runner is and how RE changes over time. In order to determine whether changes in RE are real or not, careful standardisation of footwear, time of test and nutritional status are required to limit typical error of measurement. Under controlled conditions, RE is a stable test capable of detecting relatively small changes elicited by training or other interventions. When tracking RE between or within groups it is important to account for BM. As VO2 during submaximal exercise does not, in general, increase linearly with BM, reporting RE with respect to the 0.75 power of BM has been recommended. A number of physiological and biomechanical factors appear to influence RE in highly trained or elite runners. These include metabolic adaptations within the muscle such as increased mitochondria and oxidative enzymes, the ability of the muscles to store and release elastic energy by increasing the stiffness of the muscles, and more efficient mechanics leading to less energy wasted on braking forces and excessive vertical oscillation. Interventions to improve RE are constantly sought after by athletes, coaches and sport scientists. Two interventions that have received recent widespread attention are strength training and altitude training. Strength training allows the muscles to utilise more elastic energy and reduce the amount of energy wasted in braking forces. Altitude exposure enhances discrete metabolic aspects of skeletal muscle, which facilitate more efficient use of oxygen. The importance of RE to successful distance running is well established, and future research should focus on identifying methods to improve RE. Interventions that are easily incorporated into an athlete's training are desirable.

The PubMed link to this article is here:

COMMENT: There are very few published studies looking at factors affecting running economy and speed. Of course, this study does not describe PowerCranks as a "recent intervention" but I suspect that is because the authors had never heard of us and they had no studies to support running improvement. That being said, PowerCranks do several things that should enhance running ability from improving VO2max to changing any number of physiological and biomechanical factors mentioned. In addition, PowerCranks "are easily incorporated into an athlete' training" which is desirable.

 

2. Tips on maximizing your running economy

While not a study per se, this article is well referenced regarding running economy. Again, you will find much of what is said is influenced by PowerCranks training.

Tips on maximizing your running economy

Greg Crowther

This is an article written for a magazine and publshed on the web that is well referenced with scientific studies. Here is an interesting excerpt: "An interesting follow-up study on stride length was conducted by Morgan et al. (Journal of Applied Physiology 77: 245-51, 1994). They examined 45 recreational runners and, like Cavanagh & Williams, found that most demonstrated a near-optimal stride length for the speed at which they were tested. However, nine of the runners were diagnosed as overstriders and were subsequently trained to reduce their strides to a more optimal length. After three weeks of training, these nine showed significant improvements in running economy relative to a control group."

Read the entire article here

 

Injury and rehabilitation

1. Factors associated with recurrent hamstring injuries

A published study trying to look at all the factors associated with hamstring injury. One will find that many of the factors are addressed by training on PowerCranks

Factors associated with recurrent hamstring injuries.

Croisier JL.

ABSTRACT

A history of muscle injury represents a predominant risk factor for future insult in that muscle group. The high frequency of re-injury and persistent complaints after a hamstring strain comprise major difficulties for the athlete on return to athletic activities. Some of the risk factors associated with the possible recurrence of the injury are, in all probability, already implicated in the initial injury. One can distinguish between those events peculiar to the sport activity modalities (extrinsic factors) and other contributing factors based on the athletes individual features (intrinsic factors). For both categories, the persistence of mistakes or abnormalities in action represent an irrefutable component contributing to the re-injury cycle. Additional factors leading to chronicity can come from the first injury per se through modifications in the muscle tissue and possible adaptive changes in biomechanics and motor patterns of sporting movements. We emphasise the role of questionable approaches to the diagnosis process, drug treatment or rehabilitation design. To date, the risk factors examined in the literature have either been scientifically associated with injury and/or speculated to be associated with injury. In this context, quantifying the real role of each factor remains hypothetical, the most likely ones corresponding to inadequate warm-up, invalid structure and the content of training, muscle tightness and/or weakness, agonist/antagonist imbalances, underestimation of an extensive injury, use of inappropriate drugs, presence of an extensive scar tissue and, above all, incomplete or aggressive rehabilitation. Such a list highlights the unavoidable necessity of developing valid assessment methods, the use of specific measurement tools and more rigorous guidelines in the treatment and rehabilitation. This also implies a scientific understanding as well as specifically qualified medical doctors, physiotherapists and trainers acting in partnership.

The PubMed link to this article is here:

COMMENT: Of course, many factors can cause injury, some of them out of the control of the athlete. However, many of the listed potential risk factors listed above are addressed by training or rehabilitation with PowerCranks. Specifically, PowerCranks address weaknesses and specifically prevent agonist/antagonist imbalances and prevent incomplete rehabilitation because diagnosis of continued weakness and injury is so obvious.

 

2. Preseason strength and flexibility imbalance associated with athletic injuries in female collegiate athletes

Find out how muscle imbalance is one of the major factors leading to injuries in these athletes. Muscle imbalances is one of the major areas addressed by PowerCranks in both rehabilitation and injury prevention programs.

Preseason strength and flexibility imbalances associated with athletic injuries in female collegiate athletes

Joseph J. Knapik, et. al.

ABSTRACT

One hundred thirty-eight female collegiate athletes, participating in eight weightbearing varsity sports, were administered preseason strength and flexibility tests and followed for injuries during their sports seasons. Strength was measured as the maximal isokinetic torque of the right and left knee flexors and knee extensors at 30 and 180 deg/sec. Flexibility was measured as the active range of motion of several lower body joints. An athletic trainer evaluated and recorded injuries occurring to the athletes in practice or competition. Forty percent of the women suffered one or more injuries. Athletes experienced more lower extremity injuries if they had: 1) a right knee flexor 15% stronger than the left knee flexor at 180 deg/sec; 2) a right hip extensor 15% more flexible than the left hip extensor; 3) a knee flexor/knee extensor ratio of less than 0.75 at 180 deg/sec. There was a trend for higher injury rates to be associated with knee flexor or hip extensor imbalances of 15% or more on either side of the body. These data demonstrate that specific strength and flexibility imbalances are associated with lower extremity injuries in female collegiate athletes.

The PubMed link to this article is here:

COMMENT: Notice how the recurrent theme of muscle imbalance associated with injury

keeps occurring regardless of the sport or injury being described. Specifically, PowerCranks prevent or rehabilitate agonist/antagonist and right left imbalances of the lower extremity and core and can be useful for injury reduction in any sport.