A counterweight is not necessary to implement simple, natural and comfortable single-leg cycle training Thomas E. Dolmage, Rachael A. Evans & Roger S. Goldstein
European Journal of Applied Physiology ISSN 1439-6319 Volume 114 Number 11 Eur J Appl Physiol (2014) 114:2455-2456 DOI 10.1007/s00421-014-2948-0
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Author's personal copy Eur J Appl Physiol (2014) 114:2455–2456 DOI 10.1007/s00421-014-2948-0
LETTER TO THE EDITOR
A counterweight is not necessary to implement simple, natural and comfortable single‑leg cycle training Thomas E. Dolmage · Rachael A. Evans · Roger S. Goldstein
Received: 5 June 2014 / Accepted: 25 June 2014 / Published online: 16 July 2014 © Springer-Verlag Berlin Heidelberg 2014
Dear Editor, Reading the article “Cardiovascular responses to counterweighted single-leg cycling: implications for rehabilitation” that appeared in the May 2014 edition of the European Journal of Applied Physiology (Burns et al. 2014), we thought it might be helpful to add another perspective. Burns et al. accurately presented the evidence that singleleg cycle training of patients with chronic obstructive pulmonary disease (COPD) is more effective than conventional training (Bjørgen et al. 2009; Dolmage and Goldstein 2008). By partitioning muscle activity, thereby reducing the ventilatory load, the ventilatory limited patient can increase the peripheral muscle stimulus compared to conventional two-legged cycling. This translates to improved whole body exercise. However, contrary to the conclusions of their article, a counterweight is not necessary to implement simple, effective and tolerable single-leg cycle training when the appropriate ergometer design is chosen. The mechanism within ergometers which drive the heavy flywheel that provides resistance can be either freeor fixed-wheel designs. We presume Burns used a standard, i.e. unmodified, free-wheeling ergometer. A free-wheel, the standard for safety reasons, is essentially a simple ratchet system consisting of a toothed wheel (pinion) and a pivoting, spring-loaded finger (pawl). When stationary or rotated This letter refers to the article doi:10.1007/s00421-014-2830-0. Communicated by Klaas R. Westerterp/Håkan Westerblad. T. E. Dolmage (*) · R. S. Goldstein West Park Healthcare Centre, Toronto, ON, Canada e-mail:
[email protected] R. A. Evans University of Leicester, Leicester, UK
counter-clockwise (back pedaling), the pawl slides over the gently sloped teeth and will not engage the pinion to drive the flywheel. When rotated clock-wise (forward pedaling), the pawl locks against the steeply sloped edge of the tooth, engaging the pinion. Because the rotating pedal is not always engaged with the flywheel, the non-targeted flexors of the leg must pull the pedal up so that the targeted leg is in position for the next stroke. We agree that, when using standard free-wheel ergometers, the recruitment of the less powerful and more fatigable knee and hip flexors makes this activity “unnatural, uncomfortable, hard to coordinate and subsequently an unfavorable exercise modality”. Moreover, it does not partition the exercise but merely redistributes it. Burns et al. demonstrated that affixing a counterweight to the ‘inactive’ pedal, lessening the need for flexor muscle activity, enabled more tolerable single-leg cycling using a free-wheeling ergometer. A simpler option is to implement single-leg cycling using a fixed wheel system. This system does not have the free-wheel ratchet system installed. With a fixed wheel, the rotating pedal is always engaged with the heavy flywheel. Therefore, the pedal will rotate the flywheel and the flywheel will rotate the pedal. Hence, a counter-weight is not required for single-legged cycling. Moreover, this simple design may be applied to both electronically and mechanically braked systems without affecting the calibrated resistance. The studies of one-legged cycling in COPD used fixed wheel ergometers on which participants pedaled, comfortably and without practice, while resting their inactive foot on a crossbar. A counterweight was not needed on the inactive pedal because the pedal cranks remained ‘fixed’ to the heavy flywheel and its inertia carried the active leg up and over into position for the next stroke without flexor activity. Despite not using a toe clip, the foot remained in contact with the pedal confirming that it was carried and
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the leg flexors were not active. Before initiating these studies, we had confirmed that one- and two-legged pedaling a fixed-wheeled ergometer at the same power required similar oxygen uptake. We thought it important to explain the different ergometer designs so as not to discourage this easily applied training modality. We recently incorporated one-legged cycling as the principle aerobic training modality for a clinical pulmonary rehabilitation programme in COPD and found it to be feasible as well as effective. Participants enjoyed it and would recommend it to other patients. Of note, the manufacturers delivered fixed-wheel ergometers, upon request, by not installing the free-wheel sprocket that makes partitioning exercise impossible with the standard ergometer. In summary, we commend Burns’ group for bringing attention to the potential of one-legged exercise training in ventilatory limited patients. We emphasize that is an effective and simple training modality for patients with COPD in a clinical setting that can be implemented with no additional cost. Sincerely, Thomas E. Dolmage Rachael A. Evans Roger S. Goldstein
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References Bjørgen S, Hoff J, Husby VS, Hoydal MA, Tjonna AE, Steinshamn S, Richardson RS, Helgerud J (2009) Aerobic high intensity one and two legs interval cycling in chronic obstructive pulmonary disease: the sum of the parts is greater than the whole. Eur J Appl Physiol 106(4):501–507. doi:10.1007/s00421-009-1038-1 Burns KJ, Pollock BS, Lascola P, McDaniel J (2014) Cardiovascular responses to counterweighted single-leg cycling: implications for rehabilitation. Eur J Appl Physiol 114(5):961–968. doi:10.1007/ s00421-014-2830-0 Dolmage TE, Goldstein RS (2008) Effects of one-legged exercise training of patients with COPD. Chest 133(2):370–376. doi:10.1378/chest.07-1423
