Limb Hemodynamic Responses to a Single Bout of Inspiratory Muscle Strength Training

Abstract

BackgroundInspiratory muscle strength training (IMST) has been shown to bring about improvements in respiratory muscle strength and reductions in blood pressure after 6 weeks of daily high intensity training. However, there has been little investigation into the effects of IMST on limb blood flow, and it is unclear how hemodynamics are altered within a single bout of training.PurposeTo investigate the acute effects of one session of either low or high intensity IMST on blood flow in the upper and lower limbs.MethodsParticipants (n=7, 57% female) aged 20 to 47 years completed two randomized laboratory visits wherein resting blood flow was measured via duplex Doppler ultrasound at the left brachial and popliteal arteries. Following baseline measures, participants' maximal inspiratory pressure (PImax) was measured using a PowerBreathe K3 device. Participants performed one session (30 breaths) of IMST at either 15% or 75% of their PImax, and blood flow was measured again at each artery for five breaths during the final ten breaths of the training. At their second visit, subjects performed whichever training level had yet to be completed and blood flow was assessed as described above.ResultsMean blood flow at the brachial artery appeared reduced during both 15% (p=0.070) and 75% training (p=0.078), which may be attributed to a significant increase in retrograde blood flow in both cases (p=0.014 and p=0.037, respectively). This increase in retrograde blood flow tended to be greater during the 75% training (p=0.066). Popliteal artery blood flow showed similar trends to brachial artery blood flow.ConclusionsWhile IMST appears to reduce brachial artery mean blood flow during a single training session, this may be due to alterations in retrograde blood flow, which tended to increase in an intensity‐dependent manner. Further investigation into the chronic hemodynamic effects of IMST is warranted.