The influence of added mass on muscle activation and contractile mechanics during submaximal and maximal countermovement jumping in humans

Abstract

Muscle contractile mechanics induced by the changing demands of human movement have the potential to influence our movement strategies. This study examined fascicle length changes of the triceps surae during jumping with added mass or increasing jump height to determine whether the chosen movement strategies were associated with relevant changes in muscle contractile properties. Sixteen participants jumped at sub-maximal and maximal intensities while total net work was matched via two distinct paradigms: (1) adding mass to the participant or (2) increasing jump height. Electromyography (EMG) and ultrasound analyses were performed to examine muscle activation, fascicle length and fascicle velocity changes of the triceps surae during jumping. Integrated EMG was significantly higher in the added mass paradigm with no difference in mean or maximal EMG, indicating that the muscle was activated for a significantly longer period of time but not activated to a greater intensity. Fascicle shortening velocity was slower with added mass compared than with increasing jump height; therefore, intrinsic forcevelocity properties probably enabled increased force production. Improved fascicle contractile mechanics paired with a longer activation period probably produced a consistently larger fascicle force, enabling a greater impulse about the ankle joint. This may explain why previous research found that participants used an anklecentred strategy for work production in the added mass paradigm and not in the jump height paradigm. The varied architecture of muscles within the lower limb may influence which muscles we choose to employ for work production under different task constraints.

Muscle Actuators, Not Springs, Drive Maximal Effort Human Locomotor Performance

“…The power model involves a large amount of muscle work (Biewener, 1998). Therefore, the observed optimal performance no longer becomes a factor of tendon storage of elastic energy and efficiency, but of single maximal force contractility of the muscle (Wade et al, 2019). Humans may have the capability to use their muscle-tendon unit in both capacities.…”

Effects of Surface Properties on Gastrocnemius Medialis and Vastus Lateralis Fascicle Mechanics During Maximal Countermovement Jumping

“…Our hypothesis is that this is not the case in humans when jumping over these three sport surfaces. In comparison, ( Wade et al, 2019 ) recently demonstrated that adding mass during CMJ increased the time to perform the movement, resulting in lower shortening velocity of gastrocnemius lateralis and soleus muscles, and probably increasing their force and work generation without increasing mean or maximal EMG amplitude. In our study, we could speculate that surface properties tend to affect GM muscle activation level rather than altering the timing of muscle activation and/or the time to perform CMJ.…”

“…Previously, Kurokawa et al (2003) estimated that GM sarcomeres operated on favorable portion of the force-length curve (i.e., over the plateau and upper part of the ascending part) during CMJ, “where fascicles could generate more than 75% of the maximal” fascicle force ( Kurokawa et al, 2003 ). Previous findings in vertical jumping suggest that the difference in muscle architecture and function between the monoarticular soleus and the biarticular GM and gastrocnemius lateralis, both contributing to the generation of ankle power during the push-off phase of the CMJ, may result in different fascicle behavior and elastic mechanisms ( Kurokawa et al, 2003 ; Farris et al, 2016 ; Wade et al, 2019 ). It is also possible that soleus fascicle behavior was affected on the more deformable surfaces and contributed to the greater ankle plantar flexion velocity observed in this study.…”

“…Maximal vertical jumping performance mainly depends on the mechanical power generated by the lower limb muscle-tendon units (MTU) during the push-off phase ( Bobbert et al, 1986 ; Anderson and Pandy, 1993 ; Kurokawa et al, 2003 ; Farris et al, 2016 ; Nikolaidou et al, 2017 ; Wade et al, 2019 ). As such, jumping movement has been analyzed in light of muscle and tendon behaviors ( Bobbert et al, 1986 ; Anderson and Pandy, 1993 ; Kurokawa et al, 2003 ; Farris et al, 2016 ; Nikolaidou et al, 2017 ; Wade et al, 2019 ) and there is evidence for a decoupling mechanism between muscle fascicles and joint motion thanks to the compliance of the tendinous tissues ( Alexander, 1974 ; Holt, 2019 ). Specifically, tendinous tissues (connective tissues: extracellular matrix, aponeurosis, tendon) can act like springs by storing elastic strain energy and rapidly releasing it to power body movements ( Alexander and Bennet-Clark, 1977 ; Roberts, 2016 ).…”

“…This “catapult-like” mechanism allows the amplification of MTUs’ power outputs far beyond the contractile power capabilities of the muscle ( Alexander and Bennet-Clark, 1977 ; Roberts and Azizi, 2011 ). These mechanical interactions between muscle and tendon are modulated by the nervous system, and the level and timing at which a muscle is activated directly influences power amplification by the tendinous tissues ( Anderson and Pandy, 1993 ; Bobbert et al, 1996 ; Wade et al, 2019 ) as well as the direction of energy flow (e.g., from muscle to tendon to body) ( Roberts and Azizi, 2011 ; Roberts, 2019 ). During jumping, a proximal-to-distal timing of leg muscle excitation patterns from the hip to the ankle was previously reported ( Bobbert and van Ingen Schenau, 1988 ; Voigt et al, 1995 ).…”