Respiratory Muscle Fatigue in a Mountain Ultramarathon Race
Respiratory Muscle Fatigue in a Mountain Ultramarathon Race
Ultramarathon Performance. Approximately 2500 runners participated, and 85% successfully finished the race (83% of the study participants finished). The average time to complete the race for participants in the present study was 20.1 ± 3.4 h (range, 13.8–25.8 h), resulting in an average velocity of 5.3 ± 0.9 km·h. All participants were able to cover the final kilometer of the race (over a flat portion of the track) at a much higher pace (average, 12.1 ± 1.7 km·h; range, 9.8–16.8 km·h) than their respective average velocity.
Respiratory Muscle Strength. Average and individual changes in MIP, MEP, Pm,tw, and VA are displayed in Figure 2. One participant did not perform any respiratory strength measurement, three participants only performed volitional strength measurements (MIP and MEP), and three participants Pm,tw could not be assessed appropriately after the race because of technical problems; thus, the number of participants varies slightly among parameters. Both MIP and MEP were significantly reduced (P < 0.01, n = 22) after the race, along with significant decrease in Pm,tw (P < 0.01, n = 16) and a tendency for VA to be reduced (P = 0.09, n = 16). Twitch contraction time before (96 ± 13 ms) and after (94 ± 8 ms) remained unchanged (P = 0.35, n = 16), whereas maximal rate of pressure development after the race (578 ± 195 cm H2O·s) was significantly lower than that before the race (702 ± 185 cm H2O·s, P < 0.01, n = 16).
(Enlarge Image)
Figure 2.
Individual changes in Pm,tw (n = 16), volitional MIP (n = 22), MEP (n = 22), and VA (n = 16) from before (set at 100%) to after the race. Open circles represent individual data, whereas closed circles depict average values. *Significantly different from values before the race, P < 0.01.
End-expiratory lung volume before cervical magnetic stimulation did not differ between measurements before and after the race, with an average change of 0.017 ± 0.075 mL (P = 0.39), corresponding to 0.5% ± 1.6% of FRC. The average within-session coefficient of variation (CV) for Pm,tw was 7.1% ± 3.6%.
Lung Function. Absolute values and relative changes in lung function parameters and maximal voluntary ventilation (MVV) are given in Table 2. One participant could not perform lung function measurements after the race because of airway irritation. Apart from FVC, all lung function parameters were significantly reduced after the race (P < 0.05, n = 22). Reductions in variables of respiratory muscle strength and reductions in peak inspiratory flow (PIF), peak expiratory flow (PEF), and MVV were not correlated.
Results
Ultramarathon Performance. Approximately 2500 runners participated, and 85% successfully finished the race (83% of the study participants finished). The average time to complete the race for participants in the present study was 20.1 ± 3.4 h (range, 13.8–25.8 h), resulting in an average velocity of 5.3 ± 0.9 km·h. All participants were able to cover the final kilometer of the race (over a flat portion of the track) at a much higher pace (average, 12.1 ± 1.7 km·h; range, 9.8–16.8 km·h) than their respective average velocity.
Respiratory Muscle Strength. Average and individual changes in MIP, MEP, Pm,tw, and VA are displayed in Figure 2. One participant did not perform any respiratory strength measurement, three participants only performed volitional strength measurements (MIP and MEP), and three participants Pm,tw could not be assessed appropriately after the race because of technical problems; thus, the number of participants varies slightly among parameters. Both MIP and MEP were significantly reduced (P < 0.01, n = 22) after the race, along with significant decrease in Pm,tw (P < 0.01, n = 16) and a tendency for VA to be reduced (P = 0.09, n = 16). Twitch contraction time before (96 ± 13 ms) and after (94 ± 8 ms) remained unchanged (P = 0.35, n = 16), whereas maximal rate of pressure development after the race (578 ± 195 cm H2O·s) was significantly lower than that before the race (702 ± 185 cm H2O·s, P < 0.01, n = 16).
(Enlarge Image)
Figure 2.
Individual changes in Pm,tw (n = 16), volitional MIP (n = 22), MEP (n = 22), and VA (n = 16) from before (set at 100%) to after the race. Open circles represent individual data, whereas closed circles depict average values. *Significantly different from values before the race, P < 0.01.
End-expiratory lung volume before cervical magnetic stimulation did not differ between measurements before and after the race, with an average change of 0.017 ± 0.075 mL (P = 0.39), corresponding to 0.5% ± 1.6% of FRC. The average within-session coefficient of variation (CV) for Pm,tw was 7.1% ± 3.6%.
Lung Function. Absolute values and relative changes in lung function parameters and maximal voluntary ventilation (MVV) are given in Table 2. One participant could not perform lung function measurements after the race because of airway irritation. Apart from FVC, all lung function parameters were significantly reduced after the race (P < 0.05, n = 22). Reductions in variables of respiratory muscle strength and reductions in peak inspiratory flow (PIF), peak expiratory flow (PEF), and MVV were not correlated.
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