Abstract
PurposeNeural drive and contractile properties are well-defined physiological determinants of explosive strength, the influence of muscle architecture and related morphology on explosive strength is poorly understood. The aim of this study was to examine the relationships between Quadriceps muscle architecture (pennation angle [ΘP] and fascicle length [FL]) and size (e.g., volume; QVOL), as well as patellar tendon moment arm (PTMA) with voluntary and evoked explosive knee extension torque in 53 recreationally active young men.MethodFollowing familiarisation, explosive voluntary torque at 50 ms intervals from torque onset (T50, T100, T150), evoked octet at 50 ms (8 pulses at 300-Hz; evoked T50), as well as maximum voluntary torque, were assessed on two occasions with isometric dynamometry. B-mode ultrasound was used to assess ΘP and FL at ten sites throughout the quadriceps (2–3 sites) per constituent muscle. Muscle size (QVOL) and PTMA were quantified using 1.5 T MRI.ResultThere were no relationships with absolute early phase explosive voluntary torque (≤ 50 ms), but θP (weak), QVOL (moderate to strong) and PTMA (weak) were related to late phase explosive voluntary torque (≥ 100 ms). Regression analysis revealed only QVOL was an independent variable contributing to the variance in T100 (34%) and T150 (54%). Evoked T50 was also related to QVOL and θP. When explosive strength was expressed relative to MVT there were no relationships observed.ConclusionIt is likely that the weak associations of θP and PTMA with late phase explosive voluntary torque was via their association with MVT/QVOL rather than as a direct determinant.
Highlights
Communicated by Olivier Seynnes.Explosive strength can be defined as the ability to increase force or torque as quickly as possible during a rapid voluntary contraction from a low or resting level (Maffiuletti et al 2016)
As there were no relationships between θP, or any musculoskeletal factors, and relative expressions of explosive strength, these findings suggest that any influence of these musculoskeletal factors on explosive strength is via maximum strength rather than a direct and independent effect on explosive strength per se
Muscle size measures had a more pronounced relationship with evoked than voluntary explosive strength, but surprisingly FL and moment arm were unrelated to evoked explosive strength, and θP was weakly associated with evoked explosive strength, this association was no greater than with voluntary explosive strength
Summary
Communicated by Olivier Seynnes.Explosive strength can be defined as the ability to increase force or torque as quickly as possible during a rapid voluntary contraction from a low or resting level (Maffiuletti et al 2016). There has been a growing appreciation of the functional significance of explosive strength, in situations where the time to generate torque is limited; for instance in sprinting and jumping (Weyand et al 2010; Tillin et al 2013b) and during injury-related situations (e.g., anterior cruciate ligament tears within ≤ 50 ms after landing; (Krosshaug et al 2007; Koga et al 2010)). European Journal of Applied Physiology (2021) 121:1099–1110 explosive strength appears to be important for balance, including responding to perturbations and the avoidance of falls in older adults (Izquierdo et al 1999; Pijnappels et al 2008; Bento et al 2010; Behan et al 2018), and has been related to subjective and objective measures of function in musculoskeletal patients (e.g., osteoarthritis; Maffiuletti et al 2010; Winters and Rudolph 2014; Hsieh et al 2015)). The functional importance of explosive strength highlights the need to understand its physiological determinants
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