Sport-Specific Capacity to Use Elastic Energy in the Patellar and Achilles Tendons of Elite Athletes

Abstract

Introduction: During running and jumping activities, elastic energy is utilized to enhance muscle mechanical output and efficiency. However, training-induced variations in tendon spring-like properties remain under-investigated. The present work extends earlier findings on sport-specific profiles of tendon stiffness and cross-sectional area to examine whether years of distinct loading patterns are reflected by tendons' ability to store and return energy.Methods:Ultrasound scans were performed to examine the morphological features of knee extensor and plantar flexor muscle-tendon units in elite ski jumpers, distance runners, water polo players, and sedentary controls. Tendon strain energy and hysteresis were measured with combined motion capture, ultrasonography, and dynamometry.Results: Apart from the fractional muscle-to-tendon cross-sectional area ratio being lower in the knee extensors of ski jumpers (−31%) and runners (−33%) than in water polo players, no difference in the considered muscle-tendon unit morphological features was observed between groups. Similarly, no significant difference in tendon energy storage or energy return was detected between groups. In contrast, hysteresis was lower in the patellar tendon of ski jumpers (−33%) and runners (−30%) compared to controls, with a similar trend for the Achilles tendon (significant interaction effect and large effect sizes η2 = 0.2). Normalized to body mass, the recovered strain energy of the patellar tendon was ~50% higher in ski jumpers than in water polo players and controls. For the Achilles tendon, recovered strain energy was ~40% higher in ski jumpers and runners than in controls.Discussion: Advantageous mechanical properties related to tendon spring-like function are observed in elite athletes whose sport require effective utilization of elastic energy. However, the mechanisms underpinning the better tendon capacity of some athletes to retain elastic energy could not be ascribed to intrinsic or morphological features of the lower limb muscle-tendon unit.

The Free Achilles Tendon Is Shorter, Stiffer, Has Larger Cross-Sectional Area and Longer T2* Relaxation Time in Trained Middle-Distance Runners Compared to Healthy Controls

“…The Achilles tendon stores and recovers strain energy to improve mechanical energy generation-absorption of the triceps surae muscles and reduce metabolic cost during dynamic activities ( Alexander and Bennet-Clark, 1977 ; Roberts et al, 1997 ; Lichtwark and Wilson, 2005 ; Wiesinger et al, 2017 ). In vivo studies have shown that Achilles tendon geometry and/or mechanical properties adapt to long-term mechanical loading in a manner that is specific to the type and duration of the applied loads ( Bohm et al, 2015 ; Wiesinger et al, 2015 , 2016 ).…”

Muscle‐tendon morphology and function following long‐term exposure to repeated and strenuous mechanical loading

“…In terms of the exact mechanism behind the differences in fascicle behavior and EMG activity between the groups, we hypothesize that this is related to the chronic repetitive overloading experienced by the cadets 12,18,57 . We are unable to detect the location of these physiological adaptations, but it is reasonable to assume that changes in the elastic elements of the MTU (eg, altered tendon and aponeuroses stiffness) might have facilitated the more economical function of the contractile elements of the cadets' triceps surae muscles.…”

“…Although a primary scientific consensus regarding short to medium exposure (<20 weeks) to external overloading and its effects on knee and ankle musculotendinous structures has been gradually formulated, 2,5,6,9 the evidence on long‐term exposure is more variable. The studies examining adaptations to prolonged overloading (>6 months) have mainly targeted specific populations (eg, long‐distance runners) who had undergone some years of habitual overloading due to their routine physical activity 7,10‐18 . This is understandable as long‐term monitoring designs with pre‐post measurements pose considerable challenges to the researcher.…”

Tendon Adaptations to Eccentric Exercise and the Implications for Older Adults

“…Finally, when comparing concentric and eccentric contractions, it is worth noting that the overwhelming majority of research is carried out on lower limb tendons (patellar and Achilles). This apparent bias may be due to their specific role within energy retention and power amplification during movement [31,32]. Thus, both the patellar and Achilles tendon have high functional significance and, hence, high research interest.…”