Abstract
PurposeExamine the mechanical alterations associated with repeated treadmill sprinting performed in HOT (38°C) and CON (25°C) conditions.MethodsEleven recreationally active males performed a 30-min warm-up followed by three sets of five 5-s sprints with 25-s recovery and 3-min between sets in each environment. Constant-velocity running for 1-min at 10 and 20 km.h-1 was also performed prior to and following sprinting.ResultsMean skin (37.2±0.7 vs. 32.7±0.8°C; P<0.001) and core (38.9±0.2 vs. 38.8±0.3°C; P<0.05) temperatures, together with thermal comfort (P<0.001) were higher following repeated sprinting in HOT vs. CON. Step frequency and vertical stiffness were lower (-2.6±1.6% and -5.5±5.5%; both P<0.001) and contact time (+3.2±2.4%; P<0.01) higher in HOT for the mean of sets 1–3 compared to CON. Running distance per sprint decreased from set 1 to 3 (-7.0±6.4%; P<0.001), with a tendency for shorter distance covered in HOT vs. CON (-2.7±3.4%; P = 0.06). Mean vertical (-2.6±5.5%; P<0.01), horizontal (-9.1±4.4%; P<0.001) and resultant ground reaction forces (-3.0±2.8%; P<0.01) along with vertical stiffness (-12.9±2.3%; P<0.001) and leg stiffness (-8.4±2.7%; P<0.01) decreased from set 1 to 3, independently of conditions. Propulsive power decreased from set 1 to 3 (-16.9±2.4%; P<0.001), with lower propulsive power values in set 2 (-6.6%; P<0.05) in HOT vs. CON. No changes in constant-velocity running patterns occurred between conditions, or from pre-to-post repeated-sprint exercise.ConclusionsThermal strain alters step frequency and vertical stiffness during repeated sprinting; however without exacerbating mechanical alterations. The absence of changes in constant-velocity running patterns suggests a strong link between fatigue-induced velocity decrements during sprinting and mechanical alterations.
Highlights
IntroductionAccelerating over short distances is crucial in many team sports, where short-duration efforts (e.g., accelerated runs over 10–30 m or 3–5 s) are commonplace [1]
Accelerating over short distances is crucial in many team sports, where short-duration efforts are commonplace [1]
Step frequency and vertical stiffness were lower (-2.6±1.6% and -5.5±5.5%; both P
Summary
Accelerating over short distances is crucial in many team sports, where short-duration efforts (e.g., accelerated runs over 10–30 m or 3–5 s) are commonplace [1]. Continuous measurement of the kinetics/kinematics and calculation of spring-mass model characteristics have been performed using this treadmill to elucidate some of the biomechanical correlates of fatigue when sprinting repeatedly in temperate conditions [6,7,8]. These studies demonstrated an increase in contact time along with reductions in step frequency and vertical stiffness during a single series of repeated running sprints
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