Effects of including sprints during prolonged cycling on hormonal and muscular responses and recovery in elite cyclists

This study investigated the acute effects of including 30-second sprints during prolonged low-intensity cycling on muscular and hormonal responses and recovery in elite cyclists. Twelve male cyclists (VO2max, 73.4 +/- 4.0 mL/kg/min) completed a randomized crossover protocol, wherein 4 hours of cycling at 50% of VO2max were performed with and without inclusion of three sets of 3 x 30 seconds maximal sprints (E&S vs E, work-matched). Muscle biopsies (m. vastus lateralis) and blood were sampled at Pre, immediately after (Post) and 3 hours after (3 h) finalizing sessions. E&S led to greater increases in mRNA levels compared with E for markers of fat metabolism (PDK4, Delta-Log2 fold change between E&S and E +/- 95%CI Post; 2.1 +/- 0.9, Delta 3h; 1.3 +/- 0.7) and angiogenesis (VEGFA, Delta 3h; 0.3 +/- 0.3), and greater changes in markers of muscle protein turnover (myostatin, Delta Post; -1.4 +/- 1.2, Delta 3h; -1.3 +/- 1.3; MuRF1, Delta Post; 1.5 +/- 1.2, all P < .05). E&S showed decreased mRNA levels for markers of ion transport at 3h (Na+-K+ alpha 1; -0.6 +/- 0.6, CLC1; -1.0 +/- 0.8 and NHE1; -0.3 +/- 0.2, all P < .05) and blunted responses for a marker of mitochondrial biogenesis (PGC-1 alpha, Post; -0.3 +/- 0.3, 3h; -0.4 +/- 0.3, P < .05) compared with E E&S and E showed similar endocrine responses, with exceptions of GH and SHBG, where E&S displayed lower responses at Post (GH; -4.1 +/- 3.2 mu g/L, SHBG; -2.2 +/- 1.9 nmol/L, P < .05). Both E&S and E demonstrated complete recovery in isokinetic knee extension torque 24 hours after exercise. In conclusion, we demonstrate E&S to be an effective exercise protocol for elite cyclists, which potentially leads to beneficial adaptations in skeletal muscle without impairing muscle recovery 24 hours after exercise.