Contraction type influences the human ability to use the available torque capacity of skeletal muscle during explosive efforts

The influence of contraction type on the human ability to utilise the torque capacity of skeletal muscle during explosive efforts has not been documented. Fourteen male participants completed explosive voluntary contractions of the knee extensors in four separate conditions: concentric (CON) and eccentric (ECC); and isometric at two knee angles (101°, ISO101; and 155°, ISO155). In each condition torque was measured at 25-ms intervals up to 150-ms from torque onset, and then normalised to the maximum voluntary torque (MVT) specific to that joint angle and angular velocity. Explosive voluntary torque after 50-ms in each condition was also expressed as a percentage of torque generated after 50-ms during a supramaximal 300-Hz electrically evoked octet in the same condition. Explosive voluntary torque normalised to MVT was >60% larger in CON than any other condition after the initial 25-ms. The percentage of evoked torque expressed after 50-ms of the explosive voluntary contractions was also greatest in CON (ANOVA; P<0.001), suggesting higher concentric volitional activation. This was confirmed by greater agonist EMG normalised to Mmax (recorded during the explosive voluntary contractions) in CON. These results provide novel evidence that the ability to utilise the muscle’s torque capacity explosively is influenced by contraction type, with concentric contractions being more conducive to explosive performance due to a more effective neural strategy.