ADAPTATIONS IN TRICEPS SURAE MUSCLE-TENDON UNIT MECHANICAL PROPERTIES IN ELITE JUMPERS

The purpose of this study was to analyse the triceps surae (TS) muscle-tendon unit (MTU) mechanical properties (muscle strength, maximal tendon strain and tendon stiffness) in elite track and field jumpers (long jump, triple jump, high jump, pole vault) over several years, in order to examine potential alterations in the uniformity of adaptation within the TS MTU. The findings demonstrated a higher TS muscle strength and tendon stiffness for the take-off leg in comparison to the swing leg, irrespective of the jumping discipline. Similar symmetry indexes for muscle strength and tendon stiffness indicated to a uniform TS MTU adaptation in healthy elite track and field jumpers. Longitudinal investigation demonstrated greater fluctuations in TS MTU properties over one year in elite jumpers compared to age-matched controls, predominantly for the take-off leg, irrespective of the training period (preparation vs. competition period). Nevertheless, athletes with lower adaptive similarities between muscle and tendon adaptation may experience temporary increased demand on the tendon and potentially be at greater risk for tendon injuries

Improving Trip- and Slip-Resisting Skills in Older People:Perturbation Dose Matters

Aging negatively affects balance recovery responses after trips and slips. We hypothesize that older people can benefit from brief treadmill-based trip and slip perturbation exposure despite reduced muscular capacities, but with neuropathology, their responsiveness to these perturbations will be decreased. Thus, to facilitate long-term benefits and their generalizability to everyday life, one needs to consider the individual threshold for perturbation dose

MUSCLE-TENDON ADAPTATION MONITORING IN ELITE ATHLETES: PRELIMINARY RESULTS FROM A LONGITUDINAL INVESTIGATION

In this study, we analysed the triceps surae (TS) muscle-tendon unit (MTU) mechanical properties (muscle strength and tendon stiffness) in elite jumping event athletes (long jump, triple jump, high jump, pole vault) and monitored the training-induced alterations in these properties over one year in nine elite jumpers, in order to detect potential changes in the uniformity of adaptation within the TS MTU. The findings indicate to a higher TS muscle strength and Achilles tendon stiffness in the take-off leg in comparison to the swing leg. The longitudinal monitoring revealed a concordant muscle and tendon adaptation in the TS MTU in both legs in the selected athletes

Effects of triceps surae muscle strength and tendon stiffness on the reactive dynamic stability and adaptability of older female adults during perturbed walking

This study aimed to examine whether the triceps surae (TS) muscle-tendon unit (MTU) mechanical properties affect gait stability and its reactive adaptation potential to repeated perturbation exposure in older adults. Thirty-four older adults each experienced eight separate unexpected perturbations during treadmill walking, while a motion capture system was used to determine the margin of stability (MoS) and base of support (BoS). Ankle plantar flexor muscle strength and Achilles tendon (AT) stiffness were analyzed using ultrasonography and dynamometry. A median split and separation boundaries classified the subjects into two groups with GroupStrong (n = 10) showing higher ankle plantar flexor muscle strength (2.26 +/- 0.17 vs. 1.47 +/- 0.20 N center dot m/kg, means +/- SD: P < 0.001) and AT stiffness (544 +/- 75 vs. 429 +/- 86 N/mm; P = 0.004) than GroupWeak in = 12). The first perturbation caused a negative Delta MoS (MoS in relation to unperturbed baseline walking) at touchdown of perturbed step (Pert(R)), indicating an unstable position. GroupStrong required four recovery steps to return to Delta MoS zero level, whereas GroupWeak was unable to return to baseline within the analyzed steps. However, after repeated perturbations, both groups increased Delta MoS at touchdown of Pert(R) with a similar magnitude. Significant correlations between Delta BoS and Delta MoS at touchdown of the first recovery step and TS MTU capacities (0.41 < r < 0.57: 0.006 < P < 0.048) were found. We conclude that older adults with TS muscle weakness have a diminished ability to control gait stability during unexpected perturbations, increasing their fall risk, but that degeneration in muscle strength and tendon stiffness may not inhibit the ability of the locomotor system to adapt the reactive motor response to repeated perturbations. NEW & NOTEWORTHY Triceps surae muscle weakness and a more compliant Achilles tendon partly limit older adults' ability to effectively enlarge the base of support and recover dynamic stability after an unexpected perturbation during walking, increasing their fail risk. However, the degeneration in muscle strength and tendon stiffness may not inhibit the ability of the locomotor system to adapt the reactive motor response to repeated perturbations

MATCHING TRICEPS SURAE MUSCLE STRENGTH AND TENDON STIFFNESS ELIMINATES AGE-RELATED DIFFERENCES IN DROP-JUMP PERFORMANCE

We aimed to determine the influence of triceps surae (TS) muscle strength and Achilles tendon (AT) stiffness on age-related changes in locomotor performance and motor task execution strategy during a drop jump (DJ) task. After matching 12 young and 12 middleaged adults for TS muscle strength and AT stiffness, all subjects performed a series of DJs from different starting heights. Matched young and middle-aged adults showed similar DJ performance but the middle-aged adults showed significantly longer ground contact times, lower values in maximum vertical ground reaction force during the support phase and lower mechanical power, independent of starting height. These results suggest that leg extensor muscle strength and tendon stiffness are the primary drivers of age-related changes in locomotor performance, but not motor task execution strategy selection during jumping

Differences in run-up, take-off, and flight characteristics: successful vs. unsuccessful high jump attempts at the IAAF world championships

Studies previously conducted on high jump have yielded important information regarding successful performance. However, analyses in competitive scenarios have often disregarded athletes’ unsuccessful attempts. This study aimed to investigate the biomechanical differences between successful and unsuccessful jumps during competition. High-speed video footage (200 Hz) was obtained from 11 athletes during the 2018 Men's World Athletics Indoor Championship Final. From each athlete, one successful (SU) and one unsuccessful (UN) jump at the same bar height were included in the analysis, leaving seven athletes in total. Following whole-body 3D manual digitization, several temporal and kinematic variables were calculated for the run-up, take-off, and flight phases of each jump. During SU jumps, athletes raised the center of mass to a greater extent (p < 0.01) from take-off. Touchdown in SU jumps was characterized by a faster anteroposterior velocity (p < 0.05), lower backward lean (p < 0.05), and changes in joint angles for the stance and trail limbs (p < 0.05). Athletes also shortened the final contact time during SU jumps (p < 0.01) after producing a longer flight time in the final step of the run-up (p < 0.05). Elite-level high jumpers undertake a series of adjustments to successfully clear the bar after UN jumps. These adjustments reinforce the importance of the run-up in setting the foundations for take-off and bar clearance. Furthermore, the findings demonstrate the need for coaches to be mindful of the adjustments required in stance and trail limbs when looking to optimize feedback to athletes during training and competition

Evidence of a Uniform Muscle-Tendon Unit Adaptation in Healthy Elite Track and Field Jumpers: A Cross Sectional Investigation

Different adaptive responses to mechanical loading between muscle and tendon can lead to non-uniform biomechanical properties within the muscle-tendon unit. The current study aimed to analyze the mechanical properties of the triceps surae muscle-tendon unit in healthy male and female elite track and field jumpers in order to detect possible inter-limb differences and intra-limb non-uniformities in muscle and tendon adaptation. The triceps surae muscle strength and tendon stiffness were analyzed in both limbs during maximal voluntary isometric plantar flexion contractions using synchronous dynamometry and ultrasonography in sixty-seven healthy young male (n = 35) and female (n = 32) elite international level track and field jumpers (high jump, long jump, triple jump, pole vault). Triceps surae muscle-tendon unit intra-limb uniformity was assessed using between limb symmetry indexes in the muscle strength and tendon stiffness. Independent from sex and jumping discipline the take-off leg showed a significantly higher (p &lt; 0.05) triceps surae muscle strength and tendon stiffness, suggesting different habitual mechanical loading between legs. However, despite these inter-limb discrepancies no differences were detected in the symmetry indexes of muscle strength (5.9 ± 9.4%) and tendon stiffness (8.1 ± 11.5%). This was accompanied by a significant correlation between the symmetry indexes of muscle strength and tendon stiffness (r = 0.44; p &lt; 0.01; n = 67). Thus, the current findings give evidence for a uniform muscle-tendon unit adaptation in healthy elite track and field jumpers, which can be reflected as a protective mechanism to maintain its integrity to meet the functional demand