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 trainin… Show more
“…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.…”
Section: R5 R10supporting
confidence: 85%
“…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, ).…”
Section: Methodsmentioning
confidence: 99%
“…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.…”
The purpose of this study was to investigate the relationship between fatigue‐induced reductions in isometric 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 seven young males and six young females. All measurements were performed with both legs. For dorsiflexion, fatigue‐related time‐course changes in isometric maximal voluntary contraction (MVC) torque, angular velocity, dynamic torque, and power production following repeated maximal isotonic contractions (load: 20% MVC) were investigated before, immediately after, and 1, 2, 5 and 10 min after a fatiguing task. There were no relationships between the fatigue‐related reductions in isometric MVC torque and peak power at any timepoint, suggesting that fatigue‐induced reductions in isometric MVC torque does not entirely reflect fatigue‐induced changes in dynamic performance. The relative contribution of fatigue‐related reduction in dynamic torque on power loss was greater immediately following the task, and lower throughout recovery than the corresponding decrease in angular velocity. Thus, power loss immediately following the task was more strongly related to the decline in dynamic torque; however, this relationship shifted throughout recovery to a greater dependence on slowing of angular velocity for power loss.
“…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.…”
Section: R5 R10supporting
confidence: 85%
“…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, ).…”
Section: Methodsmentioning
confidence: 99%
“…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.…”
The purpose of this study was to investigate the relationship between fatigue‐induced reductions in isometric 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 seven young males and six young females. All measurements were performed with both legs. For dorsiflexion, fatigue‐related time‐course changes in isometric maximal voluntary contraction (MVC) torque, angular velocity, dynamic torque, and power production following repeated maximal isotonic contractions (load: 20% MVC) were investigated before, immediately after, and 1, 2, 5 and 10 min after a fatiguing task. There were no relationships between the fatigue‐related reductions in isometric MVC torque and peak power at any timepoint, suggesting that fatigue‐induced reductions in isometric MVC torque does not entirely reflect fatigue‐induced changes in dynamic performance. The relative contribution of fatigue‐related reduction in dynamic torque on power loss was greater immediately following the task, and lower throughout recovery than the corresponding decrease in angular velocity. Thus, power loss immediately following the task was more strongly related to the decline in dynamic torque; however, this relationship shifted throughout recovery to a greater dependence on slowing of angular velocity for power loss.
“…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.…”
Section: Introductionmentioning
confidence: 85%
“…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.…”
Active muscle shortening and lengthening are prevalent in all sports, and when these motions precede an isometric (ie, constant muscle-tendon unit length) contraction, they influence force production. Specifically, the amount of force produced in an isometric steady-state is less following active shortening (residual force depression; rFD) and more following active lengthening (residual force enhancement; rFE) than a purely isometric contraction at the same muscle length and level of activation. Together, rFD and rFE encompass the intrinsic property of muscle known as the history dependence of force. 1 Since the initial discovery of the history dependence of force by Abbott and Aubert in 1952, 1 rFD and rFE have been observed in single sarcomeres, 2 single human muscle fibers, 3 and humans in vivo during submaximal and maximal contraction intensities. 4-6 The modifiability of the history dependence of force through training has recently become an area of interest: if rFD can be decreased and rFE increased, there is potential to optimize sport performance. 7-10 However, no definitive conclusions have been
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