FACTORS CONTRIBUTING TO LOWER METABOLIC DEMAND OF ECCENTRIC THAN CONCENTRIC CYCLING

This study compared muscle-tendon behavior, muscle oxygenation and muscle activity between eccentric and concentric cycling exercise at the same work output to investigate why metabolic demand is lower during eccentric than concentric cycling. Eleven untrained men (27.1 ± 7.0 y) performed concentric cycling (CONC) and eccentric cycling (ECC) for 10 min (60 rpm) at 65% of the maximal concentric cycling power output (191 ± 45 W) four weeks apart. During cycling, oxygen consumption (VO₂), heart rate (HR), vastus lateralis (VL) tissue total hemoglobin (tHb) and oxygenation index (TOI) were recorded, and muscle-tendon behavior was assessed using ultrasonography. The surface electromyogram (EMG) was recorded from VL, vastus medialis (VM), rectus femoris (RF) and biceps femoris (BF) muscles, and cycling torque and knee joint angle during each revolution were also recorded. Average (-65 ± 7%) and HR (-35 ± 9%) were lower and average TOI was greater (16 ± 1%) during ECC than CONC, but tHb was similar between bouts. Positive and negative cycling peak crank torques were greater (32 ± 21% and 48 ± 24%, respectively) during ECC than CONC, but muscle-tendon unit, fascicle and tendinous tissue length changes during pedal revolutions were similar between CONC and ECC. VL, VM, RF and BF peak EMG amplitudes were smaller (24 ± 15%, 22 ± 18%, 16 ± 17% and 18 ± 9%, respectively) during ECC than CONC. These results suggest that the lower metabolic cost of eccentric than concentric cycling was mainly due to a lower level of muscle activation per torque output.

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