Modifiability of the history dependence of force through chronic eccentric and concentric biased resistance training

Abstract

The increase and decrease in steady-state isometric force following active muscle lengthening and shortening are referred to as residual force enhancement (RFE) and force depression (FD), respectively. The RFE and FD states are associated with decreased (activation reduction; AR) and increased (activation increase; AI) neuromuscular activity, respectively. Although the mechanisms have been discussed over the last 60 years, no studies have systematically investigated the modifiability of RFE and FD with training. The purpose of the present study was to determine whether RFE and FD could be modulated through eccentric and concentric biased resistance training. Fifteen healthy young adult men (age: 24 ± 2 yr, weight: 77 ± 8 kg, height: 178 ± 5 cm) underwent 4 wk of isokinetic dorsiflexion training, in which one leg was trained eccentrically (−25°/s) and the other concentrically (+25°/s) over a 50° ankle excursion. Maximal and submaximal (40% maximum voluntary contraction) steady-state isometric torque and EMG values following active lengthening and shortening were compared to purely isometric values at the same joint angles and torque levels. Residual torque enhancement (rTE) decreased by ~36% after eccentric training ( P < 0.05) and increased by ~89% after concentric training ( P < 0.05), whereas residual torque depression (rTD), AR, AI, and optimal angles for torque production were not significantly altered by resistance training ( P ≥ 0.05). It appears that rTE, but not rTD, for the human ankle dorsiflexors is differentially modifiable through contraction type-dependent resistance training. NEW & NOTEWORTHY The history dependence of force production is a property of muscle unexplained by current cross bridge and sliding filament theories. Whether a muscle is actively lengthened (residual force enhancement; RFE) or shortened (force depression) to a given length, the isometric force should be equal to a purely isometric contraction—but it is not! In this study we show that eccentric training decreased RFE, whereas concentric training increased RFE and converted all nonresponders (i.e., not exhibiting RFE) into responders.

Differential contributions of fatigue‐induced strength loss and slowing of angular velocity to power loss following repeated maximal shortening contractions

“…In accordance with previous studies (Burnley, Vanhatalo, & Jones, 2012;Pethick, Winter, & Burnley, 2018;Theurel & Lepers, 2008), we considered that doublet torque is an index of peripheral fatigue and VA is an index of central fatigue in the current study. For the dorsiflexors, complete VA is often observed during MVC (Baudry et al, 2007;Chen & Power, 2019;Cheng & Rice, 2009), and this study also found "near maximal activation" throughout ( Figure 1c) as expected. Thus, it is suggested that voluntary drive was maintained and did not explain task failure in the current study.…”

“…Two supramaximal doublet stimulations at 100 Hz were interpolated approximately 2 s after the beginning and end of contraction, respectively, for VA assessment using the following formula: VA (%) = [1 − (interpolated twitch torque/control twitch torque)] × 100. Activation value of 95% VA or higher was deemed “near maximal” (for details please see Chen & Power, ), and all participants met this condition before the fatiguing task. The reliability and validity of the ITT were ensured elsewhere (Behm, St‐Pierre, & Perez, ).…”

“…The purpose of the current study was to investigate the relationship between fatigue‐induced reductions in isometric MVC torque and isotonic power, and to quantify the extent to which the decreases in angular velocity and dynamic torque can explain the power loss immediately following an isotonic fatiguing task and throughout recovery. In the current study, the model we used was dorsiflexion because complete voluntary activation (VA) is often observed with this muscle group (Baudry, Klass, Pasquet, & Duchateau, ; Chen & Power, ; Cheng & Rice, ) during isometric MVCs, and we expected “near maximal activation” during maximal effort dynamic contractions.…”

Influence of isometric training at short and long muscle‐tendon unit lengths on the history dependence of force

“…A cross-sectional study by Siebert et al 16 observed no significant modifiability of rFE with resistance training compared to recreationally active controls. 16 A later study by Chen and Power 17 observed an increase in residual torque enhancement following 4 weeks of concentric dorsiflexion training and a decrease following eccentric training, but no changes in residual torque depression ("torque" is used here because ankle joint torque data were collected using a multi-joint dynamometer, like in the present study; for simplicity's sake, rFD and rFE are used throughout this article to refer to torque data as well). Chen and Power's approach was rooted in the idea of modifying muscle fascicle length, which is believed to at least somewhat reflect serial sarcomere number.…”

“…Pennation angle and fascicle length were determined in accordance with previous studies. 17,32,34 The angle between the fascicle and central aponeurosis was defined as pennation angle, and fascicle length was calculated in each image as the inter-aponeurosis distance divided by the sine component of pennation angle in each image ( Figure 1D). Here, the averaged inter-aponeurosis distance from the proximal, center, and distal ends of the image was used in calculations.…”