Abstract

--- - "It has been suggested that time spent at a high fraction of maximal oxygen consumption (%V-center dot $\\dot{\\mathrm{V}}$O2max) plays a decisive role for adaptations to interval training. However, previous studies examining how interval sessions should be designed to achieve a high %V-center dot $\\dot{\\mathrm{V}}$O2max have exclusively been performed in males. The present study compared the %V-center dot $\\dot{\\mathrm{V}}$O2max attained during three different 6 x 8 min interval protocols, in female (n = 11; V-center dot $\\dot{\\mathrm{V}}$O2max, 62.5 (6.4) mL min-1kg-1) and male (n = 8; V-center dot $\\dot{\\mathrm{V}}$O2max, 81.0 (5.2) mL min-1kg-1) cyclists. Mean power output during work intervals were identical across the three interval protocols, corresponding to the cyclist's 40 min maximal effort (PO40min): (1) 30 s intervals at 118% of PO40min interspersed with 15 s active recovery at 60% (30/15), (2) constant pace at 100% of PO40min (CON), and (3) altering between 60 s intervals at 110% and 60 s at 90% of PO40min (60/60). Additionally, the study explored whether the m. vastus lateralis characteristics of the cyclists (fiber type proportion, capillarization, and citrate synthase activity) were associated with the %V-center dot $\\dot{\\mathrm{V}}$O2max attained during the interval sessions. Overall, mean %V-center dot $\\dot{\\mathrm{V}}$O2max and time >= 90% of V-center dot $\\dot{\\mathrm{V}}$O2max were higher during 30/15 compared to CON (86.7 (10.1)% and 1123 (787) s versus 85.0 (10.4)% and 879 (779) s, respectively; both p <= 0.01) and 60/60 (85.6 (10.0)% and 917 (745) s, respectively; both p <= 0.05), while no difference was observed between 60/60 and CON (both p >= 0.36). During interval sessions, %V-center dot $\\dot{\\mathrm{V}}$O2max and time >= 90% of V-center dot $\\dot{\\mathrm{V}}$O2max did not differ between sexes. Skeletal muscle characteristics were not related to %V-center dot $\\dot{\\mathrm{V}}$O2max during interval sessions. In conclusion, well-trained cyclists demonstrate highest %V-center dot $\\dot{\\mathrm{V}}$O2max during 30/15, irrespective of sex and skeletal muscle characteristics." - Among the workload-matched sessions investigated (30/15, 60/60, and CON), 30/15 intervals resulted in the highest oxygen consumption and longest periods with oxygen consumption above 90% of the participant's maximal oxygen consumption. For each of the three interval sessions investigated, no significant differences between female and male participants were displayed for average fraction of maximal oxygen consumption achieved during the intervals. The m. vastus lateralis fiber type proportion, capillarization and citrate synthase activity of the participants were not related to the average fraction of maximal oxygen consumption achieved during the different interval sessions.