Effect of long‐term maximum strength training on explosive strength, neural, and contractile properties

Thomas G Balshaw,Marcel B Lanza,Jonathan P Folland,Thomas M Maden‐Wilkinson,Garry J Massey

doi:10.1111/sms.14120

Abstract

The purpose of this cross‐sectional study was to compare explosive strength and underpinning contractile, hypertrophic, and neuromuscular activation characteristics of long‐term maximum strength‐trained (LT‐MST; ie, ≥3 years of consistent, regular knee extensor training) and untrained individuals. Sixty‐three healthy young men (untrained [UNT] n = 49, and LT‐MST n = 14) performed isometric maximum and explosive voluntary, as well as evoked octet knee extension contractions. Torque, quadriceps, and hamstring surface EMG were recorded during all tasks. Quadriceps anatomical cross‐sectional area (QACSAMAX; via MRI) was also assessed. Maximum voluntary torque (MVT; +66%) and QACSAMAX (+54%) were greater for LT‐MST than UNT ([both] p < 0.001). Absolute explosive voluntary torque (25–150 ms after torque onset; +41 to +64%; [all] p < 0.001; 1.15≤ effect size [ES]≤2.36) and absolute evoked octet torque (50 ms after torque onset; +43, p < 0.001; ES = 3.07) were greater for LT‐MST than UNT. However, relative (to MVT) explosive voluntary torque was lower for LT‐MST than UNT from 100 to 150 ms after contraction onset (−11% to −16%; 0.001 ≤ p ≤ 0.002; 0.98 ≤ ES ≤ 1.11). Relative evoked octet torque 50 ms after onset was lower (−10%; p < 0.001; ES = 1.14) and octet time to peak torque longer (+8%; p = 0.001; ES = 1.18) for LT‐MST than UNT indicating slower contractile properties, independent from any differences in torque amplitude. The greater absolute explosive strength of the LT‐MST group was attributable to higher evoked explosive strength, that in turn appeared to be due to larger quadriceps muscle size, rather than any differences in neuromuscular activation. In contrast, the inferior relative explosive strength of LT‐MST appeared to be underpinned by slower intrinsic/evoked contractile properties.

Highlights

Explosive strength, the ability to increase force or torque rapidly from a low or resting level,1-3 is widely considered to be important for the performance of athletic tasks and daily living activities
Due to increases in maximum strength in these studies, but no/minor increases in absolute explosive strength, relative explosive strength decreased after MST.12-15 This might be because the intrinsic contractile properties showed a slowed timecourse independent of any changes in absolute force amplitude, principally longer evoked twitch and octet time to peak tension, and lower relative evoked explosive forces of the trained muscle after 12 weeks of maximum strength training, which was the case following explosive strength training.[12]
The prior experience (≥3 years) of maximum strength training was confirmed by the long-term maximum strength-trained (LT-MST) group's pronounced 66% greater maximum strength

Summary

Introduction

The ability to increase force or torque rapidly from a low or resting level,1-3 is widely considered to be important for the performance of athletic tasks (ie, sprinting and jumping4) and daily living activities (standing from a seated position, brisk walking[5]). Explosive strength training with short, rapid contractions performed as explosively as possible was most effective at developing explosive strength (ie, rapid, explosive force production), and maximum strength training with sustained contractions at high loads, but no emphasis on generating force quickly, was superior for developing maximum strength.[12,13] the changes in neuromuscular activation appeared to be specific to the type of training performed (ie, only explosive strength training increased explosive phase neuromuscular activation) In these isometric studies, perhaps surprisingly maximum strength training produced no benefits in early phase explosive force production (≤100 ms),[12,13] and this was the case for short-term isoinertial/dynamic maximum strength training.[14,15] isometric,[12,13] but not isoinertial,[14,15] MST increased late phase (>100 ms) explosive force production. Slower intrinsic contractile properties and no improvement in explosive phase neuromuscular activation likely explain the minor (absolute) or negative (relative) changes in explosive strength after short-term maximum strength training.[12,13] the short-term value of conventional maximum strength training for explosive strength development may appear limited

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