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Prolonged constant load cycling exercise is associated with reduced gross efficiency and increased muscle oxygen uptake
Author(s) -
Hopker J. G.,
O'Grady C.,
Pageaux B.
Publication year - 2017
Publication title -
scandinavian journal of medicine and science in sports
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.575
H-Index - 115
eISSN - 1600-0838
pISSN - 0905-7188
DOI - 10.1111/sms.12673
Subject(s) - cycling , vastus lateralis muscle , oxygen , medicine , time trial , zoology , chemistry , oxygenation , exercise physiology , vo2 max , cardiology , physical therapy , endocrinology , skeletal muscle , heart rate , biology , blood pressure , archaeology , organic chemistry , history
This study investigated the effects of prolonged constant load cycling exercise on cycling efficiency and local muscle oxygen uptake responses. Fourteen well‐trained cyclists each completed a 2‐h steady‐state cycling bout at 60% of their maximal minute power output to assess changes in gross cycling efficiency ( GE ) and muscle oxygen uptake ( mVO 2 ) at time points 5, 30, 60, 90, and 120 min. Near‐infrared spatially resolved spectroscopy ( NIRS ) was used to continually monitor tissue oxygenation of the Vastus Lateralis muscle, with arterial occlusions ( OCC ) applied to assess mVO 2 . The half‐recovery time of oxygenated hemoglobin (HbO 2 ) was also assessed pre and post the 2‐h cycling exercise by measuring the hyperemic response following a 5‐min OCC . GE significantly declined during the 2‐h cycling bout (18.4 ± 1.6 to 17.4 ± 1.4%; P < 0.01). Conversely, mVO 2 increased, being significantly higher after 90 and 120 min than at min 5 (+0.04 mlO 2 /min/100 g; P = 0.03). The half‐recovery time for HbO 2 was increased comparing pre and post the 2‐h cycling exercise (+7.1 ± 19s), albeit not significantly ( d : 0.48; P = 0.27). This study demonstrates that GE decreases during prolonged constant load cycling exercise and provides evidence of an increased mVO 2 , suggestive of progressive mitochondrial or contractile inefficiency.