Sprint start kinetics of amputee and non-amputee sprinters

The purpose of this study was to explore the relationship between the forces applied to the starting blocks and the start performances (SPs) of amputee sprinters (ASs) and non-amputee sprinters (NASs). SPs of 154 male and female NASs (100-m personal records [PRs], 9.58–14.00 s) and 7 male ASs (3 unilateral above knee, 3 unilateral below knee, 1 bilateral below knee; 100 m PRs, 11.70–12.70 s) with running specific prostheses (RSPs) were analysed during full-effort sprint starts using instrumented starting blocks that measured the applied forces in 3D. Using the NAS dataset and a combination of factor analysis and multiple regression techniques, we explored the relationship between force characteristics and SP (quantified by normalized average horizontal block power). Start kinetics were subsequently compared between ASs and NASs who were matched based on their absolute 100 m PR and their 100 m PR relative to the world record in their starting class. In NASs, 86% of the variance in SP was shared with five latent factors on which measured parameters related to force application to the rear and front blocks and the respective push-off directions in the sagittal plane of motion were loaded. Mediolateral force application had little influence on SP. The SP of ASs was significantly reduced compared to that of NASs matched on the basis of relative 100-m PR (−33.8%; d = 2.11, p < 0.001), while a non-significant performance reduction was observed when absolute 100-m PRs were used (−17.7%; d = 0.79, p = 0.09). These results are at least partially explained by the fact that force application to the rear block was clearly impaired in the affected legs of ASs

The relation between neuromechanical parameters and Ashworth score in stroke patients

Quantifying increased joint resistance into its contributing factors i.e. stiffness and viscosity ("hypertonia") and stretch reflexes ("hyperreflexia") is important in stroke rehabilitation. Existing clinical tests, such as the Ashworth Score, do not permit discrimination between underlying tissue and reflexive (neural) properties. We propose an instrumented identification paradigm for early and tailor made interventions.BioMechanical EngineeringMechanical, Maritime and Materials Engineerin

Spring-Mass behavior during exhaustive run at constant velocity in elite triathletes

Purpose: The aims of this study were i) to evaluate changes in leg-spring behavior during an exhaustive run in elite triathletes and ii) to determine whether these modifications were related to an increase in the energy cost of running (Cr). Methods: Nine elite triathletes ran to exhaustion on an indoor track at a constant velocity corresponding to 95% of the velocity associated with the maximal oxygen uptake (mean ± SD = 5.1 ± 0.3 m·s−1, time to exhaustion = 10.7 ± 2.6 min). Vertical and horizontal ground reaction forces were measured every lap (200 m) by a 5-m-long force platform system. Cr was measured from pulmonary gas exchange using a breath-by-breath portable gas analyzer. Results: Leg stiffness (−13.1%, P < 0.05) and peak vertical (−9.2%, P < 0.05) and propulsive (−7.5%, P < 0.001) forces decreased significantly with fatigue, whereas vertical stiffness did not change significantly. Leg and vertical stiffness changes were positively related with modifications of aerial time (R2 = 0.66, P < 0.01 and R2 = 0.72, P < 0.01, respectively) and negatively with contact time (R2 = 0.71, P < 0.01 and R2 = 0.74, P < 0.01, respectively). Alterations of vertical forces were related with the decrease of the angle of velocity vector at toe off (R2 = 0.73, P < 0.01). When considering mean values of oxygen uptake, no change was observed from 33% to 100% of the time to exhaustion. However, between one-third and two-thirds of the fatiguing run, negative correlations were observed between oxygen consumption and leg stiffness (R2 = 0.83, P < 0.001) or vertical stiffness (R2 = 0.50, P < 0.03). Conclusions: During a constant run to exhaustion, the fatigue induces a stiffness adaptation that modifies the stride mechanical parameters and especially decreases the maximal vertical force. This response to fatigue involves greater energy consumption

Lower limb mechanical properties: Significant References Omitted

Letter to the Edito

Vitamin and mineral supplementation and neuromuscular recovery after a running race

This double-blind study investigated the effects of vitamin and mineral complex supplementation on the neuromuscular function of the knee-extensor muscles after a prolonged trail running race

Validity of the Université de Montréal Track Test to assess the velocity associated with peak oxygen uptake for adolescents.

International audienceThe purpose of the study was to test the ability to determine the velocity associated with peak oxygen uptake for adolescents by means of a simple field test, the Université de Montréal Track Test (UMTT). Fifteen adolescents, 13.4 +/- 1.0 years, performed two maximal field tests where oxygen uptake and heart rate were continuously monitored. The first test (graded field test, first stage 8 km.h-1, increment 1.5 km.h-1, duration 3 min) allowed the subjects to reach a steady-state oxygen uptake. Then, the velocity associated with peak oxygen uptake was calculated from the ratio between peak oxygen uptake above resting level to energy cost of running. The calculated velocity was kept as the criterion velocity. For the second test (UMTT, first stage 8 km.h-1; increment 1 km.h-1; duration 2 min), the velocity measured at the last completed stage was retained. The measured peak oxygen uptake for the graded field test (51.8 +/- 6.5 ml.kg-1.min-1) and for the UMTT (51.0 +/- 7.9 ml.kg-1.min-1) were not significantly different. The calculated velocity (12.9 +/- 1.0 km.h-1) and the measured velocity (12.7 +/- 0.9 km.h-1) were not significantly different and were significantly correlated (r = 0.80, p < 0.001). It was concluded that, for adolescents, the velocity measured at the last completed stage of the UMTT allows a valid estimation of the velocity associated with peak oxygen uptake

Vitamin and mineral supplementation and neuromuscular recovery after a running race

PURPOSE: This double-blind study investigated the effects of vitamin and mineral complex supplementation on the neuromuscular function of the knee-extensor muscles after a prolonged trail running race. METHODS: Twenty-two well-trained endurance runners took either placebo (Pl group) or vitamins and minerals (Vm group) for 21 d before the race and for 2 d after the race. Maximal voluntary contractions (MVC) and surface EMG activity of the vastus lateralis (VL) muscle were recorded before (pre) and 1 h (post), 24 h (post 24) and 48 h (post 48) after the race. Central activation ratio (CAR), neural (M-wave), and contractile (muscular twitch) properties of the quadriceps muscles were analyzed using electrical stimulation techniques. RESULTS: The knee-extensor MVC was significantly (P < 0.01) reduced after exercise for both groups (Vm: 36.5 +/- 3.0 \%; Pl: 36.9 +/- 2.1\%), but MVC recovery was greater for Vm than Pl after 48 h (11\%, P < 0.05). The reduced MVC after exercise was associated with a significant reduction in maximal EMG normalized to the M-wave in VL muscle and in CAR for both groups. Characteristics of the muscular twitch were not significantly altered for either groups, whereas M-wave duration increased significantly (P < 0.05) after exercise. CONCLUSIONS: The reduction of MVC immediately after the race appeared to result from peripheral mechanisms such as a failure in muscle membrane excitation and, to a lesser extent, from reduced central activation. The cause of the depressed MVC 24 h after the race seemed to be located within the muscle itself. A dietary supplementation of a vitamin and mineral complex does not attenuate the loss of contractile function immediately after the running exercise, and it may accelerate the recovery of maximal force capacity

Visual Perception and Decision Making in Dynamic Environments. An experimental study in Beach Volleyball

Velentzas K, Vietmeier N, Pollmann D. Visual Perception and Decision Making in Dynamic Environments. An experimental study in Beach Volleyball. In: Guilhem G, Rabita G, Brocherie F, et al., eds. 28th Annual Congress of the EUROPEAN COLLEGE OF SPORT SCIENCE. Book of Abstracts. European College of Sport Science; 2023: 1052

Handcycling with concurrent lower body low-frequency electromyostimulation increases acute oxygen uptake in elite wheelchair basketball players: An acute crossover trial.

Micke F, Rappelt L, Held S, Wiedenmann T, Kleinöder H, Donath L. Handcycling with concurrent lower body low-frequency electromyostimulation increases acute oxygen uptake in elite wheelchair basketball players: An acute crossover trial. In: Guilhem G, Rabita G, Brocherie F, et al., eds. Book of Abstracts of the 28 th Annual Congress of the European College of Sport Science. 2023: 756