Effects of Pedal Speed and Crank Length on Pedaling Mechanics during Submaximal Cycling.

UNLABELLED: During submaximal cycling, the neuromuscular system has the freedom to select different intermuscular coordination strategies. From both a basic science and an applied perspective, it is important to understand how the central nervous system adjusts pedaling mechanics in response to changes in pedaling conditions. PURPOSE: To determine the effect of changes in pedal speed (a marker of muscle shortening velocity) and crank length (a marker of muscle length) on pedaling mechanics during submaximal cycling. METHODS: Fifteen trained cyclists performed submaximal isokinetic cycling trials (90 rpm, 240 W) using pedal speeds of 1.41 to 1.61 m·s(-1) and crank lengths of 150 to 190 mm. Joint powers were calculated using inverse dynamics. RESULTS: Increases in pedal speed and crank length caused large increases knee and hip angular excursions and velocities (P < 0.05), whereas ankle angular kinematics stayed relatively constant (P > 0.05). Joint moments and joint powers were less affected by changes in the independent variables, but some interesting effects and trends were observed. Most noteworthy, knee extension moments and powers tended to decrease, whereas hip extension power tended to increase with an increase in crank length. CONCLUSIONS: The distribution of joint moments and powers is largely maintained across a range of pedaling conditions. The crank length induced differences in knee extension moments, and powers may represent a trade-off between the central nervous system's attempts to simultaneously minimize muscle metabolic and mechanical stresses. These results increase our understanding of the neural and mechanical mechanisms underlying multi-joint task performance, and they have practical relevance to coaches, athletes, and clinicians.

Response to Letter to the Editor: a counterweight is not necessary to implement simple, natural and comfortable single-leg cycle training.

Dr. Dolmage and colleagues commented on a recent publication titled, "Cardiovascular responses to counterweighted single-leg cycling: implications for rehabilitation." They assert that a counterweight is not required to facilitate natural single-leg cycling, rather a fixed gear ergometer can also accomplish the same goal. We agree with Dolmage and colleagues that a fixed gear ergometer can facilitate natural single-leg cycling with minimal deviation in the angular velocity of the crank if the kinetic energy of the flywheel is large. We also present some simple comparisons between the two modalities.

Effect of crank length on joint-specific power during maximal cycling.

UNLABELLED: Previous investigators have suggested that crank length has little effect on overall short-term maximal cycling power once the effects of pedal speed and pedaling rate are accounted for. Although overall maximal power may be unaffected by crank length, it is possible that similar overall power might be produced with different combinations of joint-specific powers. Knowing the effects of crank length on joint-specific power production during maximal cycling may have practical implications with respect to avoiding or delaying fatigue during high-intensity exercise. PURPOSE: The purpose of this study was to determine the effect of changes in crank length on joint-specific powers during short-term maximal cycling. METHODS: Fifteen trained cyclists performed maximal isokinetic cycling trials using crank lengths of 150, 165, 170, 175, and 190 mm. At each crank length, participants performed maximal trials at pedaling rates optimized for maximum power and at a constant pedaling rate of 120 rpm. Using pedal forces and limb kinematics, joint-specific powers were calculated via inverse dynamics and normalized to overall pedal power. RESULTS: ANOVAs revealed that crank length had no significant effect on relative joint-specific powers at the hip, knee, or ankle joints (P > 0.05) when pedaling rate was optimized. When pedaling rate was constant, crank length had a small but significant effect on hip and knee joint power (150 vs 190 mm only) (P < 0.05). CONCLUSIONS: These data demonstrate that crank length does not affect relative joint-specific power once the effects of pedaling rate and pedal speed are accounted for. Our results thereby substantiate previous findings that crank length per se is not an important determinant of maximum cycling power production.