To investigate the neuromuscular, physiological and perceptual responses to two types of modified high-intensity running sessions typically used in rugby training environments.
Twenty-five male academy rugby union players performed two separate shuttle running protocols eight days apart. Participants completed 50 x 30 m shuttles, alternating maximal running and walking (total 3000 m), for: i) linear acceleration (SL) and ii) multidirectional change of direction with acceleration and deceleration (CoD). Measures of muscle function (i.e. knee flexion, knee extension, shallow range eccentric hamstring and thigh adductor squeeze) were recorded before and immediately after performing both protocols. Blood lactate concentration ([La]), rating of perceived exertion (RPE), heart rate (HR) and movement characteristics via a 10 Hz GPS device were recorded throughout.
Across the same distance, COD HIE demonstrated statistical (p < 0.05) differences for external load measures of HIR, TDLOW, TDMOD, LACC, MACC, LDEC, MDEC and HDEC. Between-condition significance were identified across internal load measurements of RPE (1500 m), sRPE x ET and [La], while greater neuromuscular decrements were observed across all strength measures (FlexionL/R, ExtensionLR, EccHamstringsL/R, Groin) during CoD HIE than SL.
The inclusion of CoD principals within HIE induced increased neuromuscular, physiological and perceptual measures of fatigue compared to SL HIE. It is likely the inclusion of repeated acceleration and deceleration efforts during CoD which will have most influence across the assessed markers of fatigue.