The Effects Of Age On Exercise-induced Abdominal Muscle Fatigue In Healthy Younger And Older Men.

Abstract

PURPOSE: Older men have a greater amount of expiratory flow limitation and abdominal muscle pressure generation during high intensity exercise compared to younger men. This may result in a higher prevalence of exercise-induced abdominal muscle fatigue. However, this is currently unknown. Therefore, we investigated the effects of age on exercise-induced abdominal muscle fatigue in healthy younger and older men. METHODS: Eight younger (29 ± 4 years) and eight older (69 ± 4 years) men completed a constant load cycling test at 85% of maximal power output to the limit of tolerance. The percentage of expiratory flow limitation was quantified by superimposing pre-exercise maximum flow volume loops with tidal breaths meeting or exceeding the expiratory portion of the maximum flow volume loops. Gastric pressures were measured using a micro-transducer esophageal catheter. To determine supramaximal nerve stimulation, three single twitches were obtained at intensities of 50, 60, 70, 80, 85, 90, 95, and 100% of maximal stimulator output pre-exercise. Fatigue of the abdominal muscles was assessed by measuring the reduction in magnetically evoked gastric twitch pressure (Pga,tw) responses pre- and post-exercise at 0, +15 and + 30 min. Abdominal muscle fatigue was defined as ≥10% reduction in potentiated Pga,tw relative to pre-exercise values. Comparisons between younger and older men for the prevalence of abdominal muscle fatigue were made using Fisher’s exact test. RESULTS: As the power output of the stimulator increased there were proportional increases in Pga,tw. Supramaximality was achieved from 90% for younger men (P ≥ 0.230) and from 95% for older men (P ≥ 0.940). Older men had higher expiratory flow limitation and gastric pressure time products than younger men (P < 0.05). Five of eight (63%) younger men (-28 ± 14%) vs. seven of eight (88%) older men (-37 ± 18) exhibited abdominal muscle fatigue (P = 0.038). CONCLUSION: We investigated the effects of age on exercise-induced abdominal muscle fatigue in healthy younger and older men. Older men experienced a greater amount of expiratory flow limitation and abdominal muscle pressure generation compared to younger men which resulted in a higher prevalence of exercise-induced abdominal muscle fatigue.