The combined effect of sprint interval training and blood flow restriction on critical power, capillary growth and mitochondrial proteins in trained cyclists

Sprint interval training (SIT) combined with post-exercise blood-flow restriction (BFR) is a novel method to increase maximal oxygen uptake (V̇ O2max) in trained individuals, and also provides a potent acute stimulus for angiogenesis and mitochondrial biogenesis. The efficacy to enhance endurance performance has however yet to be demonstrated. 21 trained male cyclists (V̇ O2max; 62.8 ± 3.7 ml.min-1 .kg-1 ) undertook 4 weeks of SIT (repeated 30 sec maximal sprints) either alone (CON; n = 10) or with post-exercise BFR (n = 11). Before and after training V̇ O2max, critical power (CP) and Wʹ were determined and muscle biopsies obtained for determination of skeletal muscle capillarity and mitochondrial protein content. CP increased (P = 0.001) by a similar extent following CON (287 ± 39 W to 297 ± 43 W) and BFR (296 ± 40 W to 306 ± 36 W). V̇ O2max increased following BFR by 5.9% (P = 0.02) but was unchanged after CON (P = 0.56). All markers of skeletal muscle capillarity and mitochondrial protein content were unchanged following either training intervention. In conclusion, 4 weeks of SIT increased CP, however this was not enhanced further with BFR. SIT was not sufficient to elicit changes in skeletal muscle capillarity and mitochondrial protein content with or without BFR. However, we further demonstrate the potency of combining BFR with SIT to enhance V̇ O2max in trained individuals.