Blood flow-restricted walking in older women: does the acute hormonal response associate with muscle hypertrophy?

Low-load exercise can increase serum hormones such as growth hormone (GH) concentration in young adults when combined with blood flow restriction (BFR), but it is unclear whether walking with BFR (BFR-walk) can elevate them for older adults. Furthermore, it remained untested whether changes in these purported anabolic hormones contribute to BFR-walk-induced muscle hypertrophy. To examine the relationship between the acute and chronic effects of BFR-walk, seven women (age: 64 ± 2 years) performed treadmill walking with (BFR-walk) and without BFR (CON-walk) at 45% of heart rate reserve for 20 min in a randomized crossover design. During BFR-walk, subjects wore 5-cm cuffs on the proximal part of the upper legs. Blood samples were taken before (PRE), immediately after (POST-1) and 15 min post (POST-2) exercise. There was a main effect of time for GH (P<0·01) with levels increasing following exercise. In addition, there was a condition and time main effect for insulin; with insulin increasing to a greater degree with BFR at POST-2. Noradrenaline increased across time for both BFR-walk (P = 0·012) and CON-walk (P<0·001); but BFR-walk induced greater elevations at POST-1 and POST-2. The change in GH, insulin and noradrenaline was not significantly correlated with BFR-walk-induced muscle hypertrophy. These preliminary results suggest that the BFR-walk-induced elevation in the purported anabolic hormones may not have a large impact on muscle growth.