1. Effects of Inspiratory Muscle Training on Inspiratory Muscle Fatigue and Breathlessness During Exercise in Hypoxia. Seims, AL, O’Hara, JP, Cooke CB and King RFGJ Discussion IMT increased PImax by 22% which is similar to the increase of 25 and 28% observed by Downey et al. (2006) and Romer et al. (2002) respectively. IMT supported the findings of Downey et al. (2006) by reducing the amount of IMF experienced during exercise in hypoxia, however a similar effect was also shown following SHAM, although this group showed a greater IMF at baseline. Following 8 weeks of IMT, RB was reduced during the walking protocol in hypoxia, however there was no change in RB following SHAM. This preliminary study shows a reduction in IMF and RB during exercise in hypoxia following IMT, however the effect of SHAM confounds attribution due to IMT due to the large variability in response. References Borg, G.A. (1982) Psychophysical bases of perceived exertion. Med. Sci. Sports Exerc, 14, 377-381. Downey, A. E. et al. (2007) Effects of inspiratory muscle training on exercise responses in normoxia and hypoxia. Respir Physiol Neurobiol, 156, 137-46. Gudjonsdottir, M. et al. (2001) Diaphragm fatigue during exercise at high altitude: the role of hypoxia and workload. Eur Respir J, 17, 674-80. Romer, L. M. et al. (2002) Inspiratory muscle fatigue in trained cyclists: effects of inspiratory muscle training. Med Sci Sports Exerc, 34, 785-92. Conclusion IMT may potentially attenuate the typical responses of increased breathlessness experienced during Expeditions above moderate altitudes. Aim To assess the effects of inspiratory muscle training (IMT) on inspiratory muscle fatigue (IMF) and perception of breathlessness (RB) during exercise in hypoxia and normoxia. Introduction Exercise in hypoxia increases the rate and depth of breathing, increasing the work of the inspiratory muscles and can exacerbate breathlessness compared to normoxia (Gudjonsdottir et al., 2001). IMT using inspiratory pressure threshold loading can reduce IMF and the perception of breathlessness at sea-level (Romer et al., 2002), but research into possible benefits in hypoxia is limited (Downey et al., 2006). Methods 13 participants (mean ± SD age, body mass, stature and : 31.24 ± 7.44 years, 75.34 ± 8.45 kg, 179.35 ± 4.28 cm and 57.37 ± 6.05 ml. kg -1. min -1 respectively) were matched on baseline resting maximal inspiratory muscle pressure (PImax) and completed 8 weeks of IMT [(POWERbreathe ®, HaB International Ltd (n = 7, PImax = 168.14 ± 40.67 cmH 2 O)] requiring 30 breaths twice a day at a load of 50% of PImax or sham training (SHAM, n = 6, PImax = 164.83±24.18 cmH 2 O) requiring 60 breaths twice a day at a load of 15% of PImax. All participants completed a loaded (12.5kg backpack) 39 minutes incremental walking protocol (starting at 3km. hr -1 at 1% gradient, increasing every 3 minutes to a final workload of 5km. hr -1 on a 16% gradient) in normoxia and hypoxia (~14.5% O 2, equivalent to ~3000m altitude) pre- and post-training. Maximum inspiratory muscle pressure (PImax) was measured pre and post-walking test using a respiratory pressure meter (Micromedical, Basingstoke), with the difference (ΔPImax) indicating the magnitude of IMF. Rating of breathlessness (RB) was measured every 3 minutes during the walk using a modified 10 point Borg scale (Borg, 1982). Inspiratory muscle fatigue was measured as the change in inspiratory muscle strength (MIP) pre and post the walking protocol. Ethical approval was received from Leeds Metropolitan University Carnegie Faculty ethics committee. Results Figure 1 shows that after 8 weeks, resting PImax increased following IMT (from 168.14 ± 40.67 cmH 2 O to 196.79 ± 36.70 cmH 2 O, an increase of 21.81 ± 37.53%), and showed a small increase (from 164.83 ± 24.18 to 169.92 ± 39.04 cmH 2 O, an increase of 2.42 ± 14.51%) following SHAM. Figure 2 shows that the pre-training magnitude of IMF was similar in normoxia and hypoxia. Following IMT, IMF was less in normoxia and hypoxia compared to SHAM. Following SHAM, IMF in normoxia showed a similar change, and was also attenuated to a similar extent as IMT in hypoxia, due to the initial large magnitude of IMF. Figure 3 shows that following IMT, RB was reduced during exercise in hypoxia, and showed little change in normoxia. SHAM showed little change in RB in normoxia, but RB began to increase at 30 minutes of walking exercise in hypoxia. Figure 1: Change in mean (± SD) resting PImax pre and post IMT and SHAM Figure 2: IMF during walking exercise in normoxia and hypoxia pre and post IMT or SHAM training Figure 3: Median Change in exercise Rating of Breathlessness following 8 weeks of IMT or SHAM training