Inspiratory Muscle Fatigue Significantly Affects Breathing Frequency, Stroke Rate, and Stroke Length during 200-m Front-Crawl Swimming

Abstract

The aim of the current study was to assess the impact of inspiratory muscle fatigue (IMF) on total breaths taken (f(tot)), breaths per minute (f(b)), stroke count (SC), stroke rate (SR), and stroke length (SL) during constant velocity front-crawl swimming. Eight collegiate swimmers undertook a 200-m front-crawl swim on 2 separate occasions. On 1 occasion, IMF was induced immediately before the swim (IMF trial), and on the other occasion, the swim was undertaken in the absence of IMF (control trial). Trials were administered using a randomized crossover design and at a swimming velocity equivalent to 85% of race pace: Pilot testing identified this as being the fastest pace, which did not induce IMF. Maximal inspiratory mouth pressure, which was measured at the mouth and from residual volume, fell by 17% (p < 0.05) in response to IMF but was unchanged in response to the swim itself (p < 0.05). When compared to the control trial, f(tot), f(b), SC, and SR increased (p < 0.05) and SL decreased (p < 0.05) in response to IMF. These data suggest that the increase in f(tot) and f(b) in the presence of IMF occurred, in part, in an attempt to alleviate dyspnea. As a result, SL decreased and SR and SC increased, although variability in the SR and SC response did occur. However, as a number of identical muscles are recruited during deep inspirations and the front-crawl arm stroke, the possibility that arm coordination was changed, in part, to compensate for a reduced force-generating capacity per arm stroke should not be overlooked.

Runners maintain locomotor–respiratory coupling following isocapnic voluntary hyperpnea to task failure

“…The maintenance of LRC despite increases in breathing frequency in the current study is more consistent with recent findings by Fabre et al (2007) and Lomax and Castle (2011). Fabre et al saw no change in degree of coordination between breathing and stroke rate (SR) during rowing in hypoxia compared to normoxia.…”

“…As such, applying the findings from this study to exercise-induced respiratory muscle fatigue necessitates caution. Nonetheless, the declines in maximal volitional mouth pressures in our highly motivated subjects following IVH were similar to, though slightly less than, those seen following exerciseinduced RMF (e.g., 10 and 7 % declines in MIP and MEP, respectively, in our subjects vs. 10-28 % in previous investigations) (Coast et al 1999;Cordain et al 1994;Lomax and Castle 2011;Lomax and McConnell 2003;Romer et al 2002). Moreover, the significant inverse correlations between change in MIP and ventilatory loads (i.e., total volume and time to fatigue) are in agreement with the concept that degree of muscular fatigue is related to muscular work, further implying that the volitional measure, despite its limitations (American Thoracic Society/European Respiratory 2002), was likely indicative of global respiratory fatigue.…”

“…As evidenced by no further declines in MIP and MEP post-exercise, the running bouts in the current study were (per design) not vigorous enough to induce RMF. It appears that exercising at intensities of 85-95 % V O 2max until exhaustion is necessary to fatigue the breathing muscles (Babcock et al 1995;Johnson et al 1993;Lomax and Castle 2011;Spengler et al 2000); whereas, subjects in the present study were working at an average of only 78 % of V O 2peak over the four 5-min stages, and they certainly did not run until exhaustion. It is possible that the metabolic milieu produced with continuous moderate-intensity running post-hyperpnea also attenuated recovery of respiratory muscle strength.…”

Inspiratory Muscle Fatigue After Race-Paced Swimming Is Not Restricted to the Front Crawl Stroke

“…Although IMF is detrimental to terrestrial exercise performance (13,15), it is only recently that its impact on swimming performance has been examined (10). However, such investigations have been restricted to the FC stroke only.…”

“…For example, Jakovljevic and McConnell (8) reported 10% more IMF (p , 0.05) when f b was reduced from 1 breath every second stroke to 1 breath every fourth FC stroke. However, ad libitum f b may actually increase during FC swimming in the presence of IMF (10). Although such an increase will permit greater oxygen uptake (20) and help to alleviate the unpleasant sensation of breathing (13), the propulsive hand force during FC swimming is likely to fall (18).…”