The acute response of tendon to loading: implications for rehabilitation

Achilles tendinopathy is a common disorder involving physically active and sedentary individuals alike. Although the processes underlying its development are poorly understood, tendinopathy is widely regarded as an ‘overuse’ injury in which the tendon fails to adapt to prevalent loading conditions. Paradoxically, there is emerging evidence that heavy eccentric loading of the Achilles tendon may be an effective conservative approach for treatment of tendinopathy, with success rates of 60–80% reported. Interestingly, loading exercises involving other forms of muscle action, such as concentric activation, have been shown to be less effective treatment options. However, little is known about the acute response of tendon to exercise at present, and there are few plausible explanatory mechanisms for the observed beneficial effects of eccentric exercise, as opposed to other forms of strain stimuli. This paper presents the findings from a series of experiments undertaken to evaluate the effect of various strain stimuli on the time-dependent response of human Achilles tendon in vivo. It was shown for the first time, that heavy resistive ankle plantarflexion/ dorsiflexion exercises induced an immediate and significant decrease in Achilles tendon thickness (~15%). While thickness returned to pre-exercise levels within 24 hours, the recovery was exponential, with primary recovery occurring in less than 6 hours post-exercise. We proposed that such a diametral strain response with tensile loading reflects collagen realignment, Poison’s effects and radial extrusion of water from the tendon core. With unloading, the recovery of tendon dimensions likely reflects the re-diffusion of water via osmotic and/or inflammatory driven processes. Interestingly, prolonged walking was found to induce a similar diametral strain response. In subsequent studies, we demonstrated that eccentric exercise resulted in a greater reduction (-21%) in Achilles tendon thickness than isolated concentric exercise alone (-5%), despite a similar loading impulse. These novel findings, coupled with observations of a reduced diametral strain response with tendon pathology, highlight the importance of fluid movement to tendon function, nutrition and health. They also provide new insights into potential mechanisms underlying Achilles tendinopathy that impact rehabilitation strategies

Evidence-based practice to improve outcomes of transfemoral amputee fitted with osseointegrated implant: from laboratory to daily recordings of the load regime

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Strength Exercise Results in an Acute Decrease in Achilles Tendon Thickness

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The effect of visual targeting on ground reaction force and temporospatial parameters of gait

Background. Visual targeting has been cited as a confounding factor for gait analysis in which measures of ground reaction force and plantar pressure are obtained. Objective. To investigate the effect of visual targeting on temporospatial and kinetic aspects of gait when small targets, such as pressure platforms, have to be used. Design. A within subjects repeated measure design was used to measure step parameters and ground reaction forces of 11 healthy volunteers. Methods. Subjects were required to walk over a 10 m walkway at a self-selected pace. A 30x24 cm target area was superimposed over a hidden Kistler force plate (60x90 cm) mounted at the midpoint of the walkway. Step parameters and ground reaction forces were measured with and without the presence of the target. Ground reaction forces were analysed within the time-domain. Results. Subjects used visual control strategies when approaching targets of similar dimensions to a pressure platform. These strategies were manifested by an increase in the variability of the step length onto the target (P0.05). Conclusions. Visual control strategies employed while walking toward a target area have no affect on ground reaction force parameters when measured within the time-domain. Relevance - These findings demonstrate that targeting a 30x24 cm target does not affect ground reaction force parameters, when a gait protocol that fine-tunes the start position is employed. The findings are relevant to gait research in which small force or pressure platforms are used to assess gait kinetics. Copyright (C) 2000 Elsevier Science Ltd

Shot trajectory parameters in gold medal stationary shot-putters during world-class competition

The parameters of the shot’s trajectory were reported for male and female gold medalists (classes F52, F53, F54 and F55) who competed at the 2000 Paralympic Games and the 2002 International Paralympic Committee (IPC) World Championships. The specific objective was to determine the magnitude of differences in these parameters across classes and genders. The release velocity of the shot increased with the performance and the classification for both males (8.30 m/s to 9.96 m/s) and females (4.58 m/s to 8.50 m/s). The measured angle of the shot’s trajectory at release also increased with the performance and the classification for both males (27.540 to 32.470) and females (9.020 to 34.520). The position of the shot from a fixed reference point at release revealed a similar trend for both males (2.01 m to 2.68 m) and females (1.16 m to 1.98 m), although it was weaker

A comparison of gait initiation and termination methods for obtaining plantar foot pressures

The midgait protocol is the most commonly used method to collect pressure platform data. Spatial limitations, however, frequently render this technique unsuitable. Alternative gait protocols have focused on gait initiation procedures in obtaining data. The current study investigated whether a commonly cited two-step gait initiation protocol, or a two-step gait termination protocol produced pressure data more representative of the criterion, midgait method. A pressure platform was used to collect data for 25 asymptomatic subjects using the midgait, two-step gait initiation and two-step gait termination walking protocols. The contact duration, percentage contact duration, peak pressure, peak force, pressure-time integral and force-time integral were calculated for seven sites within the foot. Multivariate analysis of variance with repeated measures identified significant protocol by site interactions for all variables except the force-time integral. The gait initiation protocol, although having minimal effect on peak pressures beneath the forefoot, markedly altered the relative timing parameters of the foot. In contrast, the gait termination protocol had minimal effect on temporal parameters, but resulted in a reduction in pressures beneath the forefoot. Abbreviated gait protocols are often employed in plantar pressure studies. This study suggests that the choice between a gait initiation and termination protocol is largely dependent on the gait parameter of interest. Copyright (C) 1999 Elsevier Science B.V

Achilles tendinopathy modulates force frequency characteristics of eccentric exercise

Introduction\ud \ud Previous research has demonstrated that ground reaction force (GRF) recorded during eccentric ankle exercise is characterised by greater power in the 8-12Hz bandwidth when compared to that recorded during concentric ankle exercise. Subsequently, it was suggested that vibrations in this bandwidth may underpin the beneficial effect of eccentric loading in tendon repair. However, this observation has been made only in individuals without Achilles tendinopathy. This research compared the force frequency characteristics of eccentric and concentric exercises in individuals with and without Achilles tendinopathy., \ud \ud Methods\ud \ud Eleven male adults with unilateral mid-portion Achilles tendinopathy and nine control male adults without tendinopathy participated in the research. Kinematics and GRF were recorded while the participants performed a common eccentric rehabilitation exercise protocol and a concentric equivalent. Ankle joint kinematics and the frequency power spectrum of the resultant GRF were calculated.\ud \ud Results\ud \ud Eccentric exercise was characterised by a significantly greater proportion of spectral power between 4.5 and 11.5Hz when compared to concentric exercise. There were no significant differences between limbs in the force frequency characteristics of concentric exercise. Eccentric exercise, in contrast, was defined by a shift in the power spectrum of the symptomatic limb, resulting in a second spectral peak at 9Hz, rather than 10Hz in the control limb. \ud \ud Conclusions\ud \ud Compared to healthy tendon, Achilles tendinopathy was characterised by lower frequency vibrations during eccentric rehabilitation exercises. This finding may be associated with changes in neuromuscular activation and tendon stiffness which have been shown to occur with tendinopathy and provides a possible rationale for the previous observation of a different biochemical response to eccentric exercise in healthy and injured Achilles tendons., (C)2012The American College of Sports Medicin