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Effects of unloading (HS) and loading (exercise training) on overall work capacity in rats.
Author(s) -
Silva Fatima,
Bederman Ilya,
Liggett Alex,
Cabrera Marco
Publication year - 2008
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.22.2_supplement.121
Subject(s) - treadmill , aerobic capacity , anaerobic exercise , blood lactate , respiratory exchange ratio , chemistry , aerobic exercise , incremental exercise , lactate threshold , running economy , vo2 max , medicine , basal (medicine) , zoology , heart rate , endocrinology , cardiology , physical therapy , biology , blood pressure , insulin
Physiological changes associated with muscle disuse (unloading) lead to reductive remodeling of postural muscles, which in turn, could affect aerobic capacity and reduce performance. Conversely, exercise training increases aerobic capacity and performance. Our aim was to determine the effect of altered energy states (loading/unloading) on performance. We measured O 2 uptake (VO 2 ml/kg/min), CO 2 output (VCO 2 ml/kg/min), respiratory exchange ratio (RER) and blood lactate (mmol/L). Adult rats underwent either one week of hindlimb suspension (HS) or two weeks of exercise training on a motorized treadmill, 5 d/wk, 45 min/d. Training intensity was ∼75% VO 2 max. As the result of HS, higher (∼25%) basal VO 2 , VCO 2 , and lactate were observed. Exercise training increased total running time (26±4 vs 33±3 min), peak speed (35±3 vs 43±4 m/min), VO 2 (74±16 vs 84±15), and VCO 2 (75±18 vs 85±16) during the maximal exercise test. In contrast, after HS, running time (29±4 vs 21±4), peak speed (38±4 vs 30±4), and peak lactate (7±0.4 vs 5±0.2) were markedly decreased, but no changes were observed in peak VO 2 and VCO 2 . Our data suggests that the increase in baseline values in HS animals is due to the stress of unloading. Data also shows that while HS does not affect aerobic capacity, it impairs exercise performance. On the contrary, exercise training greatly improves both physical performance and aerobic capacity.