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Mechanical Alterations to Repeated Treadmill Sprints in Normobaric Hypoxia.

Abstract：

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.

journal_name

Med Sci Sports Exerc

journal_title

Medicine and science in sports and exercise

authors

Brocherie F,Millet GP,Morin JB,Girard O

doi

10.1249/MSS.0000000000000937

subject

Has Abstract

pub_date

2016-08-01 00:00:00

pages

1570-9

issue

eissn

0195-9131

issn

1530-0315

journal_volume

pub_type

杂志文章,随机对照试验

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Mechanical Alterations to Repeated Treadmill Sprints in Normobaric Hypoxia.