Contraction speed and type influences rapid utilisation of available muscle force: neural and contractile mechanisms

TY - JOUR

T1 - Contraction speed and type influences rapid utilisation of available muscle force

T2 - neural and contractile mechanisms

AU - Tillin, Neale

AU - Pain, Matthew T.G.

AU - Folland, Jonathan

PY - 2018/12/10

Y1 - 2018/12/10

N2 - This study investigated the influence of contraction speed and type on the human ability to rapidly increase torque and utilise the available maximum voluntary torque (MVT) as well as the neuromuscular mechanisms underpinning any effects. Fifteen young, healthy males completed explosive-voluntary knee-extensions in five conditions: isometric (ISO), and both concentric and eccentric at two constant accelerations of 500°.s-2 (CONSLOW and ECCSLOW) and 2000°.s-2 (CONFAST and ECCFAST). Explosive torque and quadriceps EMG were recorded every 25 ms up to 150 ms from their respective onsets and normalised to the available MVT and EMG at MVT, respectively, specific to that joint angle and velocity. Neural efficacy (explosive Voluntary:Evoked octet torque) was also measured, and torque data were entered into a Hill-type muscle model to estimate muscle performance. Explosive torques normalised to MVT (and normalised muscle forces) were greatest in the concentric, followed by isometric, and eccentric conditions; and in the fast compared with slow speeds within the same contraction type (CONFAST>CONSLOW>ISO, and ECCFAST>ECCSLOW). Normalised explosive-phase EMG and neural efficacy were greatest in concentric, followed by isometric and eccentric conditions, but were similar for fast and slow contractions of the same type. Thus, distinct neuromuscular activation appeared to explain the effect of contraction type but not speed on normalised explosive torque, suggesting the speed effect is an intrinsic contractile property. These results provide novel evidence that the ability to rapidly increase torque/force and utilise the available MVT is influenced by both contraction type and speed, due to neural and contractile mechanisms, respectively.© 2018, The Company of Biologists Ltd. The attached document (embargoed until 22/10/2019) is an author produced version of a paper published in JOURNAL OF EXPERIMENTAL BIOLOGY uploaded in accordance with the publisher’s self- archiving policy. The final published version (version of record) is available online at the link below. Some minor differences between this version and the final published version may remain. We suggest you refer to the final published version should you wish to cite from it.

AB - This study investigated the influence of contraction speed and type on the human ability to rapidly increase torque and utilise the available maximum voluntary torque (MVT) as well as the neuromuscular mechanisms underpinning any effects. Fifteen young, healthy males completed explosive-voluntary knee-extensions in five conditions: isometric (ISO), and both concentric and eccentric at two constant accelerations of 500°.s-2 (CONSLOW and ECCSLOW) and 2000°.s-2 (CONFAST and ECCFAST). Explosive torque and quadriceps EMG were recorded every 25 ms up to 150 ms from their respective onsets and normalised to the available MVT and EMG at MVT, respectively, specific to that joint angle and velocity. Neural efficacy (explosive Voluntary:Evoked octet torque) was also measured, and torque data were entered into a Hill-type muscle model to estimate muscle performance. Explosive torques normalised to MVT (and normalised muscle forces) were greatest in the concentric, followed by isometric, and eccentric conditions; and in the fast compared with slow speeds within the same contraction type (CONFAST>CONSLOW>ISO, and ECCFAST>ECCSLOW). Normalised explosive-phase EMG and neural efficacy were greatest in concentric, followed by isometric and eccentric conditions, but were similar for fast and slow contractions of the same type. Thus, distinct neuromuscular activation appeared to explain the effect of contraction type but not speed on normalised explosive torque, suggesting the speed effect is an intrinsic contractile property. These results provide novel evidence that the ability to rapidly increase torque/force and utilise the available MVT is influenced by both contraction type and speed, due to neural and contractile mechanisms, respectively.© 2018, The Company of Biologists Ltd. The attached document (embargoed until 22/10/2019) is an author produced version of a paper published in JOURNAL OF EXPERIMENTAL BIOLOGY uploaded in accordance with the publisher’s self- archiving policy. The final published version (version of record) is available online at the link below. Some minor differences between this version and the final published version may remain. We suggest you refer to the final published version should you wish to cite from it.

KW - Concentric and eccentric contractions

KW - force-velocity relationship

KW - intrinsic contractile properties

KW - muscle strength

KW - neural activation

KW - rate of force development

U2 - 10.1242/jeb.193367

DO - 10.1242/jeb.193367

M3 - Article

SN - 0022-0949

VL - 221

JO - JOURNAL OF EXPERIMENTAL BIOLOGY

JF - JOURNAL OF EXPERIMENTAL BIOLOGY

M1 - jeb193367

ER -