Movement Strategies for Countermovement Jumping are Potentially Influenced by Elastic Energy Stored and Released from Tendons

Abstract

The preferred movement strategies that humans choose to produce work for movement are not fully understood. Previous studies have demonstrated an important contribution of elastic energy stored within the Achilles tendon (AT) during jumping. This study aimed to alter energy available for storage in the AT to examine changes in how jumpers distribute work among lower limb joints. Participants (n = 16) performed maximal and sub-maximal jumps under two paradigms, matched for increasing total work output by manipulating jump height or adding body mass. Motion capture and ground reaction force data were combined in an inverse dynamics analysis to compute ankle, knee and hip joint kinetics. Results demonstrated higher peak moments about the ankle joint with added body mass (+26 Nm), likely resulting in additional energy storage in the AT. Work at the ankle joint increased proportionally with added mass, maintaining a constant contribution (~64%) to total work that was not matched with increasing jump height (−14%). This implies greater energy storage and return by the AT with added mass but not with increased height. When total work during jumping is constant but energy stored in tendons is not, humans prioritise the use of stored elastic energy over muscle work.

Comparisons of laboratory‐based methods to calculate jump height and improvements to the field‐based flight‐time method

“…Rigid-body modeling tracks individual segments within the body; however, this method requires complex data processing, commonly uses generic geometry scaling, ignores soft tissue deformation 16 and often combines the head, arms, and trunk to form a single segment. 1,9,17 The hybrid method calculates heel-lift from marker-based video tracking and therefore only requires force plate data to be integrated once to calculate flight distance, reducing errors due to integration drift while eliminating the need for complex data processing. As this method combines two separate measurements, it is critical that data are synchronized accurately.…”

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

“…Muscle work may be increased by increasing muscle force, increasing muscle contractile length change (fibre or fascicle length change) or a combination of the two. Our previous study demonstrated that when mass was added there was an increase in peak Achilles tendon force and peak ankle moment compared with when achieving the same work output by increasing jump height (Wade et al, 2018). We postulated that the additional net work produced at the ankle in the added mass paradigm was probably due to increased force production by plantar flexor muscles.…”

“…In our previous study, net work about the hip increased similarly in the two paradigms to meet increasing net work demands. In contrast, net work at the ankle was increased to a greater extent in the added mass paradigm, which we believe is due to the influence of the compliant Achilles tendon on muscle contractile mechanics (Wade et al, 2018). To investigate this, and therefore understand the factors influencing control strategies, the underlying muscle mechanics must be examined.…”

“…Understanding how humans coordinate movement during everyday tasks necessitates the study of how we adapt movement to overcome various task constraints. Using jumping as a highly controlled multijoint movement, previous studies have examined leg joint-level control strategies as jump height was increased, finding that ankle musculature is relied on during submaximal jumps and hip musculature is relied on during maximal jumps (Vanrenterghem et al, 2004;Wade et al, 2018). Carrying added mass is a common constraint that is placed on the body during everyday life; however, there has been little research into muscular coordination under this constraint during careful experimental manipulations, such as during jumping tasks.…”

“…Carrying added mass is a common constraint that is placed on the body during everyday life; however, there has been little research into muscular coordination under this constraint during careful experimental manipulations, such as during jumping tasks. We have previously (Wade et al, 2018) designed a jumping experiment where two paradigms were used to match the total net work output during jumping, by either adding mass to the participant or increasing the required jump height. We found a distinct difference in strategy for generating the same total net work between increasing added mass or increasing jump height paradigms.…”