Functional Inspiratory Muscle Training (IMT) Improves Load Carriage Performance Greater than Traditional IMT Techniques

Abstract

The addition of thoracic loads is common in occupational groups such as the military. The positioning upon the thorax poses a unique challenge to breathing mechanics and causes respiratory muscle fatigue (RMF) following exercise. IMT techniques provide a positive impact to exercise performance as well as attenuating RMF in both health and athletic populations. However in occupational groups, despite increased inspiratory muscle strength and performance, IMT has failed to attenuate RMF, potentially limiting the performance enhancement of IMT. It has been suggested that functional inspiratory muscle training (IMTF) may elicit adaptations above that of traditional IMT techniques as it targets the inspiratory muscles throughout the length-tension range adopted during exercise. PURPOSE: To investigate the use IMTF techniques on performance in exercise tasks with thoracic load carriage. METHODS: All participants (n=17) completed 4-week foundation IMT using a Powerbreathe device (2 x 30 breaths, daily at 50% maximal inspiratory pressure (MIP), either side of a pre-loaded time-trial (LCTT) while carrying a 25 kg thoracic load. Participants were randomly assigned to either IMTF (n=9) or a maintenance group (CON, n=8) and completed 4 additional weeks of training. IMTF consisted of 3 sessions per week whilst simultaneously breathing through the training device at 50% MIP and conducting 4 predetermined core exercises. CON, comprised of 30 breaths at 50% MIP, 3 times weekly. RESULTS: Baseline LCTT was 15.93 ± 2.30 and improved to 14.73 ± 2.40 min post 4 week IMT LCTT (P &lt0.01). Post IMTF, LCTT further improved (13.59 ± 2.33 min, P &lt0.05). Relative to baseline (151 ± 36 cmH2O), MIP was greater post IMT (172 ± 39 cmH2O, P<0.05) but was similar post IMTF (179 ± 25 cmH2O, P >0.05) and CON (P>0.05). The post exercise reduction in MIP in all trials remained unchanged. CONCLUSION: IMT improves MIP and exercise performance with thoracic load carriage and the improvement is enhanced by incorporating a period of IMTF, which provides an additional ergogenic effect to exercise performance. This appears to be the result of improved coordination between core and respiratory muscle groups that are tasked heavily via load carriage exercise and IMTF. However, it did not attenuate respiratory muscle fatigue after load carriage activities.