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 (P_Imax) 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 (LC_TT) either side of a double-blind six week intervention. Prior to the intervention, P_Imax was reduced relative to baseline, post-LC and post-LC_TT in both groups (pooled data: 13 ± 7% and 16 ± 8%, respectively, p < .05) and similar changes were observed post-PLA. Post-IMT only, resting P_Imax increased +31% (p < .05) and relative to pre-IMT was greater post-LC (+19%) and post-LC_TT (+18%, p < .05), however, the relative reduction in P_Imax 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.

Keywords:

• Inspiratory muscle training
• fatigue
• load carriage
• performance

Acknowledgements

The authors would like to thank Dr Michael Johnson for proofreading the manuscript.

Ethics standards: All experimental procedures and methods of assessment used in this study were approved by the host universities ethics committee and conform to the laws of the UK.

Disclosure statement

No potential conflict of interest was reported by the authors.