Influence of exercise intensity and hypoxic exposure on physiological, perceptual and biomechanical responses to treadmill running.

Acute physiological, perceptual and biomechanical consequences of manipulating both exercise intensity and hypoxic exposure during treadmill running were determined. On separate days, eleven trained individuals ran for 45 s (separated by 135 s of rest) on an instrumented treadmill at seven running speeds (8, 10, 12, 14, 16, 18 and 20 km.h-1) in normoxia (NM, FiO2 = 20.9%), moderate hypoxia (MH, FiO2 = 16.1%), high hypoxia (HH, FiO2 = 14.1%) and severe hypoxia (SH, FiO2 = 13.0%). Running mechanics were collected over 20 consecutive steps (i.e. after running ∼25 s), with concurrent assessment of physiological (heart rate and arterial oxygen saturation) and perceptual (overall perceived discomfort, difficulty breathing and leg discomfort) responses. Two-way repeated-measures ANOVA (seven speeds × four conditions) were used. There was a speed × condition interaction for heart rate (p = 0.045, ηp2 = 0.22), with lower values in NM, MH and HH compared to SH at 8 km.h-1 (125 ± 12, 125 ± 11, 128 ± 12 vs 132 ± 10 b.min-1). Overall perceived discomfort (8 and 16 km.h-1; p = 0.019 and p = 0.007, ηp2 = 0.21, respectively) and perceived difficulty breathing (all speeds; p = 0.023, ηp2 = 0.37) were greater in SH compared to MH, whereas leg discomfort was not influenced by hypoxic exposure. Minimal difference was observed in the twelve kinetics/kinematics variables with hypoxia (p > 0.122; ηp2 = 0.19). Running at slower speeds in combination with severe hypoxia elevates physiological and perceptual responses without a corresponding increase in ground reaction forces.Highlights The extent to which manipulating hypoxia severity (between normoxia and severe hypoxia) and running speed (from 8 to 20 km.h-1) influence acute physiological and perceptual responses, as well as kinetic and kinematic adjustments during treadmill running was determined.Running at slower speeds in combination with severe hypoxia elevates heart rate, while this effect was not apparent at faster speeds.Arterial oxygen saturation was increasingly lower as running speed and hypoxic severity increased.Overall perceived discomfort (8 and 16 km.h-1) and perceived difficulty breathing (all speeds) were lower in moderate hypoxia than in severe hypoxia, whereas leg discomfort remained unchanged with hypoxic exposure.

The effects of hip- and ankle-focused exercise intervention on lower limb mechanics during single leg squat among physically active females.

OBJECTIVES: There are two types of kinetic chain in dynamic knee valgus (DKV) namely top-down (proximal origins) and bottom-up (distal origins). This study compared the influence of four-week hip- and ankle-focused exercises on lower limb mechanics during single-leg squat (SLS) among physically active females. METHODS: Thirty-six physically active females with excessive DKV were divided into either HIP, ANKLE, or control groups. The intervention groups completed exercises that focused either on the hip or ankle musculature for 12 sessions over four weeks. The SLS test protocol was performed with 3D motion capture at pre- and post-intervention. Data were analyzed with two-way ANOVA test. RESULTS: HIP group showed increased dominant knee (F (2.66) = 9.437, P = .001) and ankle (F(2.66) = 16.465, P = .001) sagittal moment during 45° SLS at post-intervention compared to ANKLE and Control groups. HIP group also showed increased hip flexion angle for dominant (F(2.66) = 12.032, P = .001) and non-dominant leg (F(2.66) = 3.618, P = .032) compared to other groups during 60° SLS. No other significant differences were observed on other variables. CONCLUSION: DKV did not show any significant changes during SLS after a four-week exercise intervention focusing on hip and ankle joints.