Inspiratory Muscle Training Improves Shuttle Run Performance in Healthy Subjects

Abstract

Background Respiratory muscle training (RMT) has been extensively investigated over the past two decades. To date no method of ventilatory muscle training has fixed load throughout range in a manner consistent with the general principles of skeletal muscle training. The purpose of this study was to assess the use of computer-generated fixed-load incremental RMT produced by the performance of repeated sustained sub-maximal inspiratory efforts (80% of maximum, generated from RV to TLC; a full range of contraction/muscle shortening) with progressively reduced recovery times in healthy volunteers. Methods A ten-week controlled study of RMT was undertaken in healthy volunteers. Twenty-two subjects (mean age 26 years: 12 women) were randomly allocated to control or training groups. Each group performed the Test of Incremental Respiratory Endurance (TIRE) set at 80% of peak, three times weekly at weeks one and ten. The training group continued with the TIRE-based RMT over the intervening eight weeks. The control group ceased RMT at the end of week one and started training again only during the tenth week of the study. Before and at completion of the investigation each participant performed the multi-stage fitness test (shuttle run) and completed visual analogue scores of dyspnoea and perception of sports performance. Results Respiratory muscle strength (RMS) and endurance (RME) increased (P < 0.002, P < 0.0001) in RMT subjects with a concurrent reduction in breathlessness (P < 0.0001) and a perception of improved sports performance (P < 0.0001). The work per breath, measured as sustained inspiratory pressure and predicted VO2 max derived from the shuttle run also increased in this group (P < 0.01, P < 0.001). Despite the increases seen in shuttle run there was no associated increase in breathlessness scored by modified Borg scale at completion of the test. There were no significant changes in any of the measured parameters in the control group. Conclusions We conclude that TIRE-based RMT set at 80% of peak through range increases RMS, single-breath work capacity and RME and that these improvements result in reduced levels of breathlessness, an increase in predicted VO2 max and a perceived improvement in sports performance. Respiratory muscle training (RMT) has been extensively investigated over the past two decades. To date no method of ventilatory muscle training has fixed load throughout range in a manner consistent with the general principles of skeletal muscle training. The purpose of this study was to assess the use of computer-generated fixed-load incremental RMT produced by the performance of repeated sustained sub-maximal inspiratory efforts (80% of maximum, generated from RV to TLC; a full range of contraction/muscle shortening) with progressively reduced recovery times in healthy volunteers. A ten-week controlled study of RMT was undertaken in healthy volunteers. Twenty-two subjects (mean age 26 years: 12 women) were randomly allocated to control or training groups. Each group performed the Test of Incremental Respiratory Endurance (TIRE) set at 80% of peak, three times weekly at weeks one and ten. The training group continued with the TIRE-based RMT over the intervening eight weeks. The control group ceased RMT at the end of week one and started training again only during the tenth week of the study. Before and at completion of the investigation each participant performed the multi-stage fitness test (shuttle run) and completed visual analogue scores of dyspnoea and perception of sports performance. Respiratory muscle strength (RMS) and endurance (RME) increased (P < 0.002, P < 0.0001) in RMT subjects with a concurrent reduction in breathlessness (P < 0.0001) and a perception of improved sports performance (P < 0.0001). The work per breath, measured as sustained inspiratory pressure and predicted VO2 max derived from the shuttle run also increased in this group (P < 0.01, P < 0.001). Despite the increases seen in shuttle run there was no associated increase in breathlessness scored by modified Borg scale at completion of the test. There were no significant changes in any of the measured parameters in the control group. We conclude that TIRE-based RMT set at 80% of peak through range increases RMS, single-breath work capacity and RME and that these improvements result in reduced levels of breathlessness, an increase in predicted VO2 max and a perceived improvement in sports performance.