THE USE OF HIGH CADENCE IN CYCLING AND THE APPLICATIONS TO RPM TM A REVIEW John Lythe MHSc, CSCS, BCom

Transcription

1 THE USE OF HIGH CADENCE IN CYCLING AND THE APPLICATIONS TO RPM TM A REVIEW John Lythe MHSc, CSCS, BCom Summary The use of high cadence in the cycling community is encouraged due to the relationship between the use of such cadences and success in elite cycling competition. Although the self-selected cadence of cyclists is usually considered higher than the scientifically estimated optimum, research suggests that muscle force and neuromuscular fatigue are reduced, and cycling power output is maximised with relatively high cadences of rpm. However, these cadences also increase the metabolic cost of cycling and reduce energy efficiency. It is therefore recommended that high cadences are used when speed and power are the key determinants of performance and that lower cadences are used when efficiency and economy are key. It does not appear that cycling at high cadences increases injury risk with the risk factors being mostly related to bike set-up and technique errors and issues around excessive training volume and sudden changes in training intensity. Although it has has been prepared with regard to outdoor cycling it appears that the literature supports the selective use of high cadence during RPM TM. If participants are appropriately skilled and fitted to their bikes then it would appear that the high cadences would increase the exercise stimulus and caloric expenditure, encourage activation of type II muscle fibres while not increasing the injury risk. Introduction RPM is an instructor-led, stationary bike-based indoor cycling program. A typical class involves a single instructor who uses an interval training model to lead participants through a routine that simulates terrain and situations similar to riding a bike outdoors. Some of the movements and positions include hill climbs, sprints and steady efforts. The bikes used during RPM TM have a heavy fly wheel and the level of frictional resistance placed on this fly wheel is one factor that determines the difficulty of the workout. Other factors to modify the exercise intensity are changes in pedalling cadence and body position. Classes have a duration of approximately 50 minutes and have the primary aim of improving the cardiovascular fitness and increasing the caloric expenditure of their participants, who range from novice to experienced. The typical exercise intensity and energy expenditure of an RPM TM class was reported by Lythe and Pfitzinger (2000). By collecting heart rates and expired gases in six subjects they found that RPM TM participants consumed 582 ± 93 calories, exercised at 78.7 ± 7.3% of HR max and exerted an aerobic demand of 36.5 ± 2.6 ml/kg/min. The science of cycling is a passion for countless athletes, coaches and academics and as a consequence the literature is heavy with research. The area is so popular that a recent review into the science of cycling had to be broken into two large 20+ page articles published by E.W. Faria et al in the journal Sports Medicine, each with over 150 references.(faria et al 2005a, Faria et al 2005b) Although the application of cycling research to RPM is relatively intuitive, it is important to remember that objective of the sport of cycling is to maximise performance whereas the primary objectives of RPM are to maximise the physiological training stimulus and to burn calories. With this in mind, the following review and discussion seeks to discuss the variable of pedalling cadence and the effects of, and issues relating to, the use of periods of high cadence during RPM classes. Pedal cadence is widely accepted as an important factor influencing the economy, power output, perceived exertion and the development of fatigue during cycling. Research into cadence has generally fallen into two categories; studies which have documented and discussed the cadences used by elite and recreational cyclists during training and competition and studies which have examined the effects of

2 cadence on a variety of physiological and biomechanical variables such as muscle activity, energy expenditure, pedal forces and aerobic efficiency. Observational research has demonstrated that elite cyclists use a wide range of cadence during competition from 130 rpm (revolutions per minute) during flat stages to 80 rpm during climbing stages.(lucia, 2001). It has been identified that the self-selected cadence that most cyclists choose to ride at is appropriate at high intensity activity levels but during low and moderate activity levels is actually higher than what would be considered the optimal cadence. This self-selected cadence varies significantly between individuals and is affected by age, experience level, maximal aerobic power, muscle fibre types, and the gradient, workload and duration of the required task.(hansen 2009) It appears that these factors combine to create a preferred cadence that becomes set in the central nervous system for each individual. Elite cyclists develop their technique to the extent that they become more efficient at higher cadences compared to recreational cyclists. The Effect of Cadence on Efficiency Despite being used by most elite cyclists it has been found that higher cadences are actually less metabolically efficient than lower cadences. When cycling at constant power outputs, higher cadences result in increased oxygen cost per unit of performance (i.e. reduced gross efficiency)(chavarren, 1999). Much of the reason for a reduced energy efficiency at higher cadences is due to the simple increase in leg movement repetitions.(takaishi et al, 1998). Bieuzen (2007) demonstrated that the most efficient cadence for energy consumption is significantly lower than self selected cadence and Hansen (2009) supported this by commenting that energy efficiency was reduced, there was a shorter time to exhaustion during a maximal cycling test and subjects took longer to complete time trials when using cadences that were faster than the self-selected cadence. In contrast to this however is the reduction in the mechanical cost of cycling when using increased cadences. Marsh et al (1997) showed, using moment based calculations that muscle movement efficiency increases at higher cadences with reductions in muscle forces and reduced neuromuscular fatigue.(abiss, 2009) It is this reduction in fatigue that may cause elite cyclists to adopt this higher than ideal cadence. The Effect of Cadence on Muscle Activity and Joint Forces The muscles work in a coordinated fashion to generate power to the crank during cycling. In the power phase or downstroke, the hip, knee and ankle joints simultaneously extend to create the pushing action, whilst in the recovery phase or upstroke, they flex together to pull the pedal back up to the top dead center of the crank cycle. It appears therefore, that the influence of cadence on the level of EMG or muscle activity depends on the muscle considered and its functional role(bieuzen 2007). In general, muscle activation levels are only slightly affected by increases in cadence. The activity of the knee extensors (vastus lateralis and vastus medialis) is reduced or unaffected whereas muscle activation of gastrocnemius lateralis and biceps femoris has been shown to slightly increase at faster pedal rates. The most significant effect of cadence is on the timing of muscle activation and coordination, particularly for proximal musculature with EMG studies indicating that muscles turn-on earlier in the crank cycle. Alterations in cadence may also influence muscle fibre recruitment patterns, largely due to decreases in muscle force levels. It is believed that a reduction in myoelectrical activity observed during high cadence cycling may indicate less recruitment of fast twitch/type II muscle fibres or, conversely, greater recruitment of slow twitch/type I muscle fibres. The pedalling movement has been divided into muscular and non-muscular components. The muscular component consists of forces or torques provided by muscular activity, while the nonmuscular component comprises all other factors that contribute to the forces or torques acting on the pedal or crank and may include gravity and inertia. Non-muscular pedal forces have been shown to increase linearly as cadence increases from 60 rpm up to 120 rpm while muscular pedal forces decrease

3 (Baum, 2003). The increase in the non-muscular component reflects an increase of the inertial influence on pedal forces at greater cadences. With the heavy flywheel used in RPM TM it seems likely that this intertia would be even greater and result in less force being required from the working muscles. The Effect of Cadence on Power Output The average power output produced over an entire pedal revolution may be determined by the following equation: Power (W) = average net effective pedal torque x average angular velocity (cadence) Based on the above formula, the average force/torque applied to the pedals over an entire pedal revolution at a fixed power output is reduced at higher cadences. This is because the torque that can be applied to the pedals during cycling is reduced at faster muscle contraction velocities [relatively more time is consumed at higher cadences by the activation and relaxation process]. To determine the effect of high pedalling cadences on maximal cycling power output Mora- Rodiguez et al (2006) recruited nine well-trained cyclists to perform a continuous, incremental cycle test either at 80rpm, 100rpm or 120rpm. Power was found to be approximately 9% lower during the 120rpm condition in comparison with 80rpm and 100rpm. Additional increases in blood lactate were also found at both the higher cadences compared to 80rpm. The Effect of Cadence on Injuries The literature relating to injuries in cycling is dominated by traumatic injuries sustained during accidents, in particular injuries to the head. Thankfully these issues do not apply to indoor cycling. Common sites for non-traumatic/overuse cycling-related injuries include the knee, neck/shoulder, hands, buttock and perineum.(dettori, 2006) In recreational cyclists, a very high number (80%+) report overuse injuries.(wilber 1995) with significant differences in causative variables for men and women. Injuries in male cyclists were most affected by distances covered per week, the use of low gears and inexperience. For female cyclists, training characteristics which had the most significant effect upon overuse injuries were frequency of training and competition and the amount of stretching before cycling. The impact of cadence on cycling injuries is only occasionally mentioned in the literature, and usually only in speculation. One such mention was the potential relationship between cadence and an overuse injury to the knee called iliotibial band friction syndrome. It was suggested that a cadence that is too high in conjunction with a high seat position may contribute to the development of this injury.(farrell, 2003) Further investigation revealed however, that other factors such as bike set-up, anatomical leg length discrepancies, varus knee alignment, excessive pronation, and external tibial rotation of more than 20 were more significant issues. Additional issues such as sudden increases in mileage, the inclusion of hills, and time trials were also linked to the injury and were assumed to be more significant than high cadence. In fact, lower cadences were reported by another author to be more responsible for injury symptoms with (Mellion, 1991) commenting that riding with a high pedal resistance is a major cause of overuse problems. Application to RPM TM and Recommendations The research presented above suggests that an increase in cadence results in a variety of changes relating to energy expenditure and efficiency, muscle activity and power output. Given that the primary objectives of RPM TM are to create an intense exercise stimulus and to burn calories it would appear that most of the cycling research findings support the occasional use of high cadences in RPM TM. Specifically: a reduction in energy economy during the high cadence periods results in a greater physical demand and an increased exercise stimulus and caloric expenditure

4 the use of both high, moderate and low cadences results in a thorough muscle activation with both fast twitch/type II muscle fibres and slow twitch/type I muscle fibres being exercised a reduction in power output presents no issue as participants are on stationary bikes and are neither measuring performance or quantitatively competing The significant and unanswered issue around the appropriateness of high cadences in RPM TM classes appears to be the safety of participants. It does not appear that any causative link between high cadences and an increase risk of knee or other injuries has been made. Non-traumatic Injury risk is most closely linked to bike set-up, sudden changes in training and poor technique.(dettori, 2006) As for any exercise programme there are a number of basic physiological principles that should be applied to RPM TM. The first principle is exercise progression. New participants should be advised to spend some time developing a base level of fitness and becoming familiar with the specific activities and skill requirements. If necessary, potential participants may be first encouraged to engage in activities that have a lower intensity level and skill requirement such as aqua aerobics or walking. Once they become involved in the RPM TM programme the periods of high cadence should be viewed as a further progression. Inexperienced and/or unfit participants should be encouraged to reduce the cadence and intensity to allow for gradual skill development. The more experienced that a participant becomes with the techniques of RPM TM the more likely they will have developed the necessary skill and fitness to appropriately exercise at the higher cadences. The principle of progression would suggest that as the skill level improves, the participant may be able to increase the maximum cadence that they achieve during the high speed tracks by a small amount per week. Also and very importantly, the more experienced that are the more likely that they will have identified and refined the ideal bike set up for their physical characteristics. Other physiological principles that apply to RPM TM are periodisation and recovery. Performing activities that require high skill levels when in a state of fatigue will not promote training adaptations and may expose the participant to increased injury risk. Consequently, participants should be encouraged to rest and recover appropriately after intense sessions and after high volume periods of exercise. It is the role of the instructor to appropriately establish the abilities of class participants and to identify if anyone is unsuitable for the task. Participants should be advised on the resistance level, cadence and body positions that are suitable for them and given feedback and refinement each session. Also of significant importance is the issue of bike-fit with correct set-up being stressed at all times to all participants. Proper bicycle fit requires careful review of bicycle selection, saddle height for proper leg extension, fore-and-aft positioning of the knee over the pedal, saddle tilt, handlebar position, and positioning of the upper body for optimum comfort. Provided these basic checks are performed then it does not appear that there are any reasons why high cadence cycling should be restricted to elite level athletes. References 1. Abbiss, C.R., Peiffer, J.J, Laursen, P.B. (2008) Optimal cadence selection during cycling. International SportMed Journal, 10(1): Baum, B.S. & Li, L. (2003) Lower extremity muscle activities during cycling are influenced by load and frequency. J Electromyography and Kinesiology 13: Bieuzen, F., Vercruyssen, F., Hausswirth, C., et al. (2007) Relationship between strength level and pedal rate. Int J Sports Med 28: Bisswalter J, Hausswirth C, Smith D, et al. (2000) Energetically optimal cadence versus freely-chosen cadence during cycling: effect of exercise duration. Int J Sports Med. 20(1): Burke, E.R. (1994) Proper fit of the bicycle. Clin Sports Med. 13(1):1-14

5 6. Chapman, A., Vicenzinoa, B., Blanch, P., Hodges, P. (2009) Do differences in muscle recruitment between novice and elite cyclists reflect different movement patterns or less skilled muscle recruitment? J Sci Med Sport 12, Chavarren J, and Calbet JA. (1999). Cycling efficiency and pedalling frequency in road cyclists. Eur J Appl Physiol Occup Physiol 80: Dettori NJ, Norvell DC. (2006) Non-traumatic bicycle injuries : a review of the literature. Sports Med. 36(1): Ettema G, Lorås HW (2009) Efficiency in cycling: a review. Eur J Appl Physiol 106: Faria, E.W. (2009) Recent advances in specific training for cycling. International SportMed Journal 10(1): Faria, E.W., Parker, D.L., Faria, I.E. (2005a) The science of cycling: physiology and training part 1. Sports Med. 35(4): Faria,E.W., Parker,D.L. & Faria, I.E. (2005b) The science of cycling. Factors affecting performance Part 2. Sports Medicine 35(4): Farrell, K.C., Reisinger, K.D., Tillman MD. (2003) Force and repetition in cycling: possible implications for iliotibial band friction syndrome. Knee 10 (1): Gregor, R. J., & Conconi, F. (2000). Anatomy, biochemistry and physiology of road cycling. In R. J. Gregor, & F. Conconi (Eds.),Road Cycling (pp. 1 17). Oxford: Blackwell Science. 15. Kohler, G., Boutellier, U. (2005) The generalized force-velocity relationship explains why the preferred pedalling rate of cyclists exceeds the most efficient one. Eur J Appl Physiol 94: Lucia, A., Hoyos, J., Chicharro, J.L. (2000) Physiological responses to professional road cycling: Climbers vs. time trialists. Int J Sports Med 2000; 21: Lucia, A., Hoyos, J., Chicharro, J.L. (2001) Preferred pedalling cadence in professional cycling. Med Sci Sports Exerc 33: Lucia, A., San Juan, A.F., Montilla, M. et al. (2004) In professional road cyclists, low pedalling cadences are less efficient. Med Sci Sports Exerc 36: Lythe, J. and Pfitzinger, P. (2000) Caloric expenditure and aerobic demand of Body Step, Body Attack, Body Combat and RPM. University of Auckland. 20. Marsh, A.P., Martin, P.E. (1997) Effect of cycling experience, aerobic power, and power output on preferred and most economical cycling cadences. Med Sci Sports Exerc 29: Marsh, A.P., Martin, P.E., (1995) The relationship between cadence and lower extremity EMG in cyclists and noncyclists, Med Sci Sports Exerc 27: Mellion M.B. (1991) Common cycling injuries. Management and prevention. Sports Med. 11(1): Mora-Rodriguez, R., Aguado-Jimenez, R. (2006) Performance at high pedal cadences in well-trained cyclists. Med Sci Sports Exerc 38: Neptune, R.R. Herzog, W. (1999) The association between negative muscle work and pedaling rate. J. Biomech. 32 (1999) Raasch, C.C., Zajac, F.E., Ma, B., & Levine, W.S. (1997). Muscle coordination of maximum-speed pedaling. J. Biomech 30: So, R. (2005) Muscle recruitment pattern in cycling: a review. Physical Therapy in Sport 6: Takaishi, T., Yamamoto, T., Ono, T., et al. (1998) Neuromuscular, metabolic and kinetic adaptations for skilled pedaling performance in cyclists. Med Sci Sports Exerc 30: Wilber, C.A, Holland, G.J., Madison, R.E., Loy, S.F. (1995) An epidemiological analysis of overuse injuries among recreational cyclists. Int J Sports Med. 16(3):201-6