Effects of Different Types of Respiratory Muscle Training on Exercise Performance in Runners

MILITARY MEDICINE, 177, 5:559, 2012 Effects of Different Types of Respiratory Muscle Training on Exercise Performance in Runners Hiromi Uemura, MS*; Claes E.G. Lundgren, MD, PhD*; Andrew D. Ray, BS, MS, PhD*; David R. Pendergast, EdD† ABSTRACT To compare two different types of respiratory muscle training on exercise performance, a protocol was devised consisting of a combination of a 4-week, 12-session resistive respiratory muscle training (RRMT) followed by a 4-week, 12-session voluntary isocapnic hyperpnea training (VIHT) and conducted in experienced runners (4 men, 4 women). Measurements before and 5 days after training included: pulmonary function (spirometry), maximal inspiratory and expiratory mouth pressures, respiratory endurance time, maximal oxygen uptake (VO2max), running time to voluntary exhaustion at 80% VO2max, blood lactate concentration, and minute ventilation. There were no statistically significant differences in pulmonary functions and VO2max post-RRMT and post-VIHT compared to pre-RMT. Following RRMT the inspiratory muscle strength had improved by 23.8 ± 30% and 18.7 ± 21.4% at rest and immediately after the running test, respectively. RRMT did not increase the time intense voluntary isocapnic ventilation could be maintained during rest while VIHT increased it (237 ± 207.8%). The duration of the endurance run was extended 17.7 ± 6.5% after RRMT and 45.5 ± 14.3% after VIHT. INTRODUCTION Respiratory limitations to physical performance during prolonged submaximal1–3 and maximal4 exercise have recently been demonstrated. The work and energy cost of breathing increases from 3–5% to 13–16% of total O2 uptake as exercise intensity increases from low to maximal intensities.5 When the respiratory muscles increase their effort, or become more fatigued, their O2 consumption increases as does their blood flow at the expense of reduced perfusion of locomotor muscles,4,6 thus reducing exercise performance.4,7 Lactate accumulation in the respiratory and locomotor muscles lead to hyperventilation and indirectly to fatigue and reduced exercise tolerance.4 Earlier studies have shown that respiratory muscle training (RMT) improves respiratory muscle performance and prolongs exercise endurance by 24 to 86% at constant submaximal rates of 60 to 85% of maximal O2 uptake. This has been demonstrated for running,8–10 rowing,11 cycling,3,12–18 and swimming.19–22 Controversy over the effects of RMT continues as some studies failed to show significant improvements in exercise performance.10,23,24 One of these studies24 did not allow enough recovery time after RMT and fatigue likely obscured the gains in exercise endurance.8 Another recent article23 failed to demonstrate a benefit of RMT during a graded maximal effort, which is well known not to reflect gains from RMT.8 It has been suggested that influences of RMT on exercise performance are psychological.24 However, several studies with positive results of RMT have used control and placebo groups.8,11,14 *Center for Research & Education in Special Environments, University at Buffalo, 124 Sherman Hall, Buffalo, NY 14214. †Department of Rehabilitation Sciences, University at Buffalo, 515 Kimball Towers, Buffalo, NY 14214. Methodological factors might influence the benefits of RMT. Different training methods such as voluntary isocapnic hyperpnea training (VIHT), resistive respiratory muscle training (RRMT), or inspiratory muscle training13,25 may have different outcomes. So, for instance, is VIHT more effective than RRMT for enhancing running endurance8 or swimming at the surface, while RRMT is superior for improving divers swimming endurance at depth.20–22 The present study employed two modes of RMT in runners: RRMT which enhances respiratory muscle strength25 followed by VIHT which improves respiratory muscle endurance.12 The hypotheses of the present study were: (a) RRMT would improve respiratory muscle strength and running endurance in a constant-load running test; (b) VIHT following RRMT would further enhance respiratory muscle endurance and endurance running performance to exhaustion; (c) combined 4-week RRMT followed by 4-week VIHT would result in enhancement of endurance exercise capacity previously shown in our laboratory for each alone.8,20 METHODS The study protocol was approved by the Human Subjects Institutional Review Board of the University and the subjects signed an informed consent form. SUBJECTS Eight healthy, nonsmoking experienced distance runners (4 men, 4 women) completed the study. They were 34 ± 5 years old, 179 ± 4 and 160 ± 2 cm tall, and weighed 79 ± 9.4 and 56.5 ± 3.6 kg (men and women, respectively). They were experienced in long-distance competitive running and maintained a constant level of training of 35 to 55 miles per week at a pace of 70 to 80% of maximal O2 uptake for the duration of the study. Their fitness levels were as follows: mean maximal O2 uptake for males 51 ± 7 mL/min/kg, range MILITARY MEDICINE, Vol. 177, May 2012 559 Respiratory Training Improves Running Performance 42 to 60 mL/min/kg and for females 43 ± 7 mL/min/kg, range 38 to 53 mL/min/kg. PROTOCOL Before the beginning of each RMT training period and approximately 4 to 5 days after the completion of each type of training (to allow respiratory muscle recovery after the training) the following baseline tests were performed: pulmonary function, maximal inspiratory and expiratory mouth pressures (PImax and PEmax), respiratory endurance time (RET), progressive maximal treadmill running test to voluntary exhaustion, and a constant-load endurance running test to voluntary exhaustion at 80% of maximal O2 uptake. Pulmonary Function Tests Pulmonary function was tested with a computerized spirometer (Morgan Spiroflow Spirometer, Model #131, P. K. Morgan, Rainham, Gillingham, Kent, UK) in accordance with American Thoracic Society standards. Seated, the subjects breathed room air from a mouthpiece and wore a nose clip. Each test was repeated three times with the highest value used for data analysis. Maximal Inspiratory and Expiratory Mouth Pressures Measurements of PImax and PEmax were measured from residual volume and total lung capacity, respectively, with a sensitive pressure transducer (Tycos, Arden, NC) while the subject wore a nose clip. They sustained each inspiratory and expiratory effort for at least 1 second. The maneuvers were performed three times with the highest values used for data analysis. Respiratory Endurance Test This was a timed, isocapnic breathing test, used to assess inspiratory and expiratory muscle endurance. It was conducted with a nose clip and a mouthpiece connected to inspiration and expiration valves and a rebreathing bag to maintain isocapnia. Bag volume was initially set at 50% of each subject’s slow vital capacity (SVC). The paced breathing frequency was selected by dividing 60% of each subject’s best maximal voluntary ventilation (MVV) in 15 seconds by the tidal volume used in the MVV test. The t (...truncated)