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. At the present time there are only two studies publically available that have studied the effects of PowerCranks directly. Other studies, both short and long term, are underway right now, and we will publish resultsas they are completed and available. These are:
Effects of short-term training using powercranks on cardiovascular fitness and cycling efficiency.
Physiological responses to training using PowerCranks on trained cyclists.
PowerCranks versus normal bicycle cranks: An EMG comparison
La coordinazione - intermuscolare nel ciclismo

Other studies:

Cycling:
Improved muscular efficiency displayed as Tour de France champion matures.
Physiological and biomechanical factors associated with elite endurance cycling performance

Running:
Factors affecting running economy in trained distance runners.
Tips on maximizing your running economy

Injury and rehabilitation:
Factors associated with recurrent hamstring injuries.
Preseason strength and flexibility imbalances associated with athletic injuries in female collegiate athletes

If you have any suggestions as to other studies (or better studies) that should be included here please contact us. feedback@powercranks.com

Effects of short-term training using powercranks on cardiovascular fitness and cycling efficiency.Mark D. Luttrell, and Jeffrey A.Potteiger
ABSTRACT
Powercranks use a specially designed clutch to promote independent pedal work by each leg during cycling. We examined the effects of 6 wk of training on cyclists using Powercranks (n = 6) or normal cranks (n = 6) on maximal oxygen consumption (O2max) and anaerobic threshold (AT) during a graded exercise test (GXT), and heart rate (HR), oxygen consumption ( O2), respiratory exchange ratio (RER), and gross efficiency (GE) during a 1-hour submaximal ride at a constant load. Subjects trained at 70% of O2max for 1 h?Ed-1, 3 d?Ewk-1, for 6 weeks. The GXT and 1-hour submaximal ride were performed using normal cranks pretraining and posttraining. The 1-hour submaximal ride was performed at an intensity equal to approximately 69% of pretraining O2max with O2, RER, GE, and HR determined at 15-minute intervals during the ride. No differences were observed between or within groups for O2max or AT during the GXT. The Powercranks group had significantly higher GE values than the normal cranks group (23.6 ?? 1.3% versus 21.3 ?? 1.7%, and 23.9 ?? 1.4% versus 21.0 ?? 1.9% at 45 and 60 min, respectively), and significantly lower HR at 30, 45, and 60 minutes and O2 at 45 and 60 minutes during the 1-hour submaximal ride posttraining. It appears that 6 weeks of training with Powercranks induced physiological adaptations that reduced energy expenditure during a 1-hour submaximal ride.

Link to study: PubMed or at The Journal of Strength and Conditioning Research: Vol. 17, No. 4, pp. 785–791, pdf

COMMENT: To be truthful, we were surprised that such a large improvement could be documented in such a short period of time. A 10% improvement in cycling efficiency in 6 weeks in unheard of, although in hindsight quite plausible as the new muscles should be well adapted within this period of time and most users are well past the coordination adaption period in this time.

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 well adapted 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.

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.

La coordinazione - intermuscolare nel ciclismo, from UNIVERSITA’ DEGLI STUDI DI URBINO, Eneko Peña, PhD

This is a study presented in a slide format in which some of the findings are presented on the internet while awaiting word on publication. It is in Italian and demonstrates that coordination changes occur when one trains with PowerCranks and if one stops training with them the changes seen will eventually be lost.

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 the study here.

Related articles and studies

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.

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. About all that can be taken from this regarding the pedaling dynamic is that those who have trained longer and harder have muscles better adapted to high power endurance riding. Even the "pushing harder" conclusion is 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 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.

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.

Tips on maximizing your running economy by 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

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.

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 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.