Author(s): GARCIA, J., SLAWINSKI, J., DORO, V., YAMASHITA, D., BROCHERIE, F., Institution: FRENCH INSTITUTE OF SPORT (INSEP), Country: FRANCE, Abstract-ID: 1693

INTRODUCTION:
Horizontal deceleration (DEC) is an eccentric-based locomotor skill underpinning all changes of velocity. While eccentric exercise is associated with transient endothelial dysfunction [1], the effects of DEC intensity during repeated-sprint ability (RSA) exercise on vascular responsiveness have not yet been explored. Therefore, this study aimed to investigate the effects of different DEC intensities during an overground RSA protocol on vastus lateralis microvascular responses and oxidative capacity.
METHODS:
Twelve participants (25±3.5 yrs) randomly performed a running RSA protocol [3 sets of 8 × 20 m; 20-s passive recovery between sprints, 5-min rest between sets] with i) self-selected DEC post-sprint (DECfree), (ii) moderate enforced DEC (DEC10; 10-m braking distance post-sprint), and (iii) intense enforced DEC (DEC5; 5-m braking distance post-sprint). DEC performances were assessed using a radar gun. Vastus lateralis oxygenation kinetics was measured using near-infrared spectroscopy (NIRS) via the tissue saturation index (TSI). A supine vascular occlusion test (VOT) was performed before the RSA protocol to assess microvascular reactivity from TSI de- and re-saturation slopes. Muscle oxidative capacity was determined immediately post-exercise using repeated arterial occlusions. TSI desaturation slopes versus time curves during occlusions, reflecting the rate of post-exercise recovery of muscle oxygen consumption, were calculated using linear regression and subsequently fitted with a mono-exponential function to derive the recovery rate constant (k) [2].
RESULTS:
Mean DEC was significantly larger in DEC5 (-3.57±0.32 m/s2) than DEC10 (-2.52±0.37 m/s2, p<0.001) and DECfree (-1.82±0.30 m/s2, p<0.001), and lower in DEC10 than DECfree (p<0.001). Baseline TSI was similar across conditions (DECfree=58±4 %, DEC10=59±6 %, DEC5=58±6 %; p=0.586). No condition effect was observed for NIRS-VOT-derived microvascular reactivity, with comparable TSI desaturation rate (DECfree=-0.10±0.04 %/s, DEC10=-0.10±0.05 %/s, DEC5=-0.11±0.08 %/s; p=0.720) and TSI reperfusion rate (DECfree=0.55±0.33 %/s, DEC10=0.67±0.30 %/s, DEC5=0.62±0.55 %/s; p=0.760). Similarly, muscle oxidative capacity also did not differ between conditions, as reflected by comparable k (DECfree=2.77±0.82 1/min, DEC10=2.52±0.91 1/min, DEC5=2.09±0.47 1/min; p=0.095).
CONCLUSION:
Microvascular reactivity assessed using a supine vascular occlusion test was comparable across conditions, with relatively low values likely related to reduced shear stress associated with body position. Despite markedly different deceleration intensities during repeated-sprint exercise, post-exercise muscle oxidative recovery kinetics were preserved. These findings suggest that acute eccentric demand imposed by deceleration do not compromise endothelial-dependent vascular control or oxygen delivery-utilization coupling at the microvascular level.

[1] Larsen, Physiol Rep, 2019
[2] Adami & Rossiter, J Appl Physiol, 2018