Enhanced torque due to eccentric preloading relates to greater ease and lower O2 cost of movement

Research Objectives: To examine relationships of stretch-shortening cycle potentiation (SSCP) with ease of movement and oxygen cost of walking at 120°/s, 180°/s, and 240°/s for 3 different ranges of movements (ROMs): small, medium and large.

Design: Cross-sectional study.

Setting: University laboratory.

Participants: Young adults; n=10; Older adults, n = 10

Interventions: Not applicable.

Main Outcome Measures: Ankle plantarflexors were assessed in random order for concentric only and eccentric-preloaded concentric muscle strength at 3 different velocities (120°/s, 180°/s, and 240°/s) at 3 different ROMs (small, medium, and large). Body-mass normalized SSCP (difference between eccentric-preloaded-concentric torque and concentric torque) was calculated for all the conditions. O2 consumption and heart rate (HR) were measured at the patient’s steady state at 0.89 m/s and 1.34 m/s.

Results: In young adults, SSCP for the middle ROM was negatively related to O2 consumption at 0.89 m/s and HR at 1.34 m/s at all velocities (p < 0.05). Additionally in the middle ROM at 240°/s, SSCP was negatively related to HR at 0.89 m/s in younger adults (p < 0.05). For the small ROM, SSCP at 180°/s was negatively related to HR at 0.89 m/s in younger adults (p < 0.05). Whereas in older adults for the small ROM, SSCP at 240°/s was positively related to O2CW at 1.34 m/s.

Conclusions: Enhanced torque after eccentric loading is related to greater ease and lower O2 cost of movement in young adults. Our data suggests differential mechanisms exist for enhanced torque after eccentric loading in older adults. Whether enhanced torque after eccentric loading affects physical activity in adults remains unknown.