Training the inspiratory muscles improves running performance when carrying a 25 kg thoracic load in a backpack

Abstract

Load carriage (LC) exercise in physically demanding occupations is typically characterised by periods of low-intensity steady-state exercise and short duration, high-intensity exercise while carrying an external mass in a backpack; this form of exercise is also known as LC exercise. This induces inspiratory muscle fatigue and reduces whole-body performance. Accordingly we investigated the effect of inspiratory muscle training (IMT, 50% maximal inspiratory muscle pressure (PImax) twice daily for six week) upon running time-trial performance with thoracic LC. Nineteen healthy males formed a pressure threshold IMT (n = 10) or placebo control group (PLA; n = 9) and performed 60 min LC exercise (6.5 km h(-1)) followed by a 2.4 km running time trial (LCTT) either side of a double-blind six week intervention. Prior to the intervention, PImax was reduced relative to baseline, post-LC and post-LCTT in both groups (pooled data: 13 ± 7% and 16 ± 8%, respectively, p < .05) and similar changes were observed post-PLA. Post-IMT only, resting PImax increased +31% (p < .05) and relative to pre-IMT was greater post-LC (+19%) and post-LCTT (+18%, p < .05), however, the relative reduction in PImax at each time point was unchanged (13 ± 11% and 17 ± 9%, respectively, p > .05). In IMT only, heart rate and perceptual responses were reduced post-LC (p < .05). Time-trial performance was unchanged post-PLA and improved 8 ± 4% after IMT (p < .05). In summary, when wearing a 25 kg backpack, IMT attenuated the cardiovascular and perceptual responses to steady-state exercise and improved high-intensity time-trial performance which we attribute in part to reduced relative work intensity of the inspiratory muscles due to improved inspiratory muscle strength. These findings have real-world implications for occupational contexts.

Whole-body active warm-up and inspiratory muscle warm-up do not improve running performance when carrying thoracic loads

“…This is surprising since AWU consistently improves running and cycling performance during exercise of a similar intensity and duration as the present study including 7 min all out cycling (Burnley et al 2005) and 800 m running timetrial performance (Ingham et al 2013). Why AWU failed to improve load carriage performance is therefore interesting especially since load carriage performance can be improved through a variety of whole body (Knapik, 1997) and inspiratory muscle training interventions (Faghy and Brown, 2015). Accordingly, the lack of effect upon performance is likely the design of the AWU.…”

Inspiratory muscle training improves exercise capacity with thoracic load carriage

“…). To date, only one study has investigated the effects of IMT on exercise performance with thoracic LC (Faghy and Brown ). While their findings that IMT improved performance in a 2.4 km running time‐trial and reduced the amount of global inspiratory muscle fatigue following exercise were novel, their primary measure of inspiratory muscle fatigue was volitional maximal inspiratory mouth pressure ( P Imax ).…”

Respiratory Effects of Thoracic Load Carriage Exercise and Inspiratory Muscle Training as a Strategy to Optimize Respiratory Muscle Performance with Load Carriage

“…Despite the potential benefits of IMT on LC exercise, only two studies to date have sought to identify whether respiratory muscle training improves physical performance during LC [29, 105]. In the first study [105], military personnel accustomed to wearing body armor completed 6 weeks of daily inspiratory muscle training (2 × 30 breath cycles set at 90% of maximal inspiratory mouth pressure).…”

“…The second study investigating the effects of IMT and LC exercise studied 19 healthy, physically active males who were habituated to recreational LC activities [29]. The authors found that 6 weeks of pressure-threshold IMT (2 × 30 breath cycles daily set at 50% of P Imax ) attenuated the cardiovascular and perceptual responses to steady-state exercise and improved running time trial performance while wearing a 25-kg backpack.…”

“…The choice of placebo in this study [29] is particularly concerning because alternative sham IMT placebo protocols that do not elicit any changes in inspiratory muscle function are well described in the literature [13, 91]. Therefore, the findings of this recent study [29], although novel, do not demonstrate significant internal and external validity when considered in the context of the limitations of the study. Thus, further investigation is warranted to confirm these findings and better describe the effects of IMT on LC exercise tolerance.…”