Mechanical Alterations to Repeated Treadmill Sprints in Normobaric Hypoxia

PURPOSE: Compelling evidence suggests larger performance decrements during hypoxic versus normoxic repeated sprinting. Yet the underlying mechanical alterations have not been thoroughly investigated. Therefore, we examined the effects of different levels of normobaric hypoxia on running mechanical performance during repeated treadmill sprinting.

METHODS: Thirteen team sport athletes performed eight 5-s sprints with 25 s of passive recovery on an instrumented treadmill in either normoxia near sea level (SL; FiO2 = 20.9%), moderate normobaric hypoxia (MH; FiO2 = 16.8%; corresponding to ~1800 m altitude), or severe normobaric hypoxia (SH; FiO2 = 13.3%; ~3600 m).

RESULTS: Net power output in the horizontal direction did not differ (P > 0.05) between conditions for the first sprint (mean ± SD, pooled values: 13.09 ± 1.97 W·kg) but was lower for the eight sprints in SH compared with SL (-7.3% ± 5.5%, P < 0.001) and MH (-7.1% ± 5.9%, P < 0.01), with no difference between SL and MH (+0.1% ± 8.0%, P = 1.00). Sprint decrement score was similar between conditions (pooled values: -11.4% ± 7.9%, P = 0.49). Mean vertical, horizontal, and resultant ground reaction forces decreased (P < 0.001) from the first to the last repetition in all conditions (pooled values: -2.4% ± 1.9%, -8.6% ± 6.5%, and -2.4% ± 1.9%). This was further accompanied by larger kinematic (mainly contact time: +4.0% ± 2.9%, P < 0.001, and +3.3% ± 3.6%, P < 0.05, respectively; stride frequency: -2.3% ± 2.0%, P < 0.01, and -2.3% ± 2.8%, P < 0.05, respectively) and spring-mass characteristics (mainly vertical stiffness: -6.0% ± 3.9% and -5.1% ± 5.7%, respectively, P < 0.01) fatigue-induced changes in SH compared with SL and MH.

CONCLUSION: In SH, impairments in repeated sprint ability and in associated kinetics/kinematics and spring-mass characteristics exceed those observed near SL and in MH (i.e., no or minimal difference). Specifically, SH accentuates the repeated sprint ability fatigue-related inability to effectively apply forward-oriented ground reaction force and to maintain vertical stiffness and stride frequency.

Medienart:	E-Artikel

Erscheinungsjahr:	2016
Erschienen:	2016

Enthalten in:	Zur Gesamtaufnahme - volume:48
Enthalten in:	Medicine and science in sports and exercise - 48(2016), 8 vom: 04. Aug., Seite 1570-9

Sprache:	Englisch

Beteiligte Personen:	Brocherie, Franck [VerfasserIn] Millet, Grégoire P [VerfasserIn] Morin, Jean-Benoit [VerfasserIn] Girard, Olivier [VerfasserIn]

Links:	Volltext

Themen:	Journal Article Randomized Controlled Trial Research Support, Non-U.S. Gov't

Anmerkungen:	Date Completed 25.09.2017 Date Revised 09.01.2018 published: Print Citation Status MEDLINE

doi:	10.1249/MSS.0000000000000937

funding:
Förderinstitution / Projekttitel:

PPN (Katalog-ID):	NLM258950323