Effects of a failure versus a submaximal low load blood flow-restriction training protocol on the Heat Shock Proteins responses

INTRODUCTION: The stress imposed to muscle fibers during blood flow restricted resistance exercise (BFRRE) is poorly investigated. Therefore, we aimed to compare the effect of a failure (FA) vs submaximal (SU) BFRRE protocol on heat-shock protein responses in the exercising muscles.
METHODS: Sixteen untrained men (18-45 yrs) completed 14 BFRRE sessions divided into 2 blocks of 7 sessions in 5 days, interspersed by 10 days of rest. Legs were randomly assigned to either FA (4 sets to voluntary failure) or SU protocol (30-, 15-, 15-, 15 reps) using unilateral knee extensions at 20% of 1 repetition maximum with 30s rest between sets. BFRRE was conducted with partial blood flow restriction (100 mmHg) induced by a 15 cm wide pressure cuff. Biopsies from the m. vastus lateralis were collected before, during and post intervention. The HSP response investigated was changes in αB-crystallin staining intensity on muscle cross sections analyzed by immunofluorescence. RESULTS: Relative to pre-exercise, a significant increase in αB-crystallin staining intensity (reflecting cytoskeletal bound proteins) was observed 2h after the first session in both legs (129 ± 18%, p<0.001 and 77 ± 10%, p<0.05; FA and SU, respectively). There were no significant difference between protocols at any time point, but these changes tended to be larger in FA legs than SU legs. During the rest period and 10 days post intervention, αB-crystallin staining intensity gradually decreased to baseline values. CONCLUSION: The αB-crystallin immunostaining analyses suggest that cytoskeletal proteins are highly stressed after the first session of both FA and SU BFRRE protocols.