News & Views from the Editor-in-Chief: Andrew M. Jones
The June issue of MSSE contains the usual array of high-quality research articles and I’ve chosen three to highlight. Firstly, in their paper ‘Improvements in Maximal Oxygen Uptake after Sprint Interval Training Coincide with Increases in Central Hemodynamic Factors’, Mandic et al. show that sprint-interval training (SIT) leads to robust increases in total hemoglobin mass (tHb), blood volume and cardiac output in parallel with the well-known increases in maximal oxygen consumption (VO2max). Furthermore, they show that tHb, together with body surface area and baseline VO2max, are important predictors of the improvements in VO2max after 6 weeks of SIT. This finding is important as it contrasts with previous research articles in which central hemodynamic factors were excluded from models explaining the mechanisms behind SIT-induced improvements in VO2max. The results of Mandic et al. suggest that both central and peripheral factors need to be considered when delineating the mechanisms behind the increased VO2max observed after SIT. Secondly, in ‘Increased Mass-Specific Maximal Fat Oxidation Rate with Small versus Large Muscle Mass Exercise’, Skettebo address the previously-unidentified mechanisms for reduced fat oxidation as exercise intensity increases. The authors hypothesised that central limitations to exercise influence the maximal fat oxidation rate (MFO). Twelve men conducted step-incremental (30-80% of VO2peak) one- and two-legged cycling exercise, and steady-state pulmonary gas exchange values were used to calculate fat oxidation rates. The mass-specific MFO (MFO divided by the lean mass of the active legs) was 52% higher during one-legged exercise and was associated with a larger exercise-induced elevation of cardiac output per active leg than during two-legged exercise (as an indicator of elevated leg blood flow). These results indicate that increased perfusion (i.e. increased oxygen and substrate deliveries) are sufficient to increase mass-specific MFO and that the skeletal muscles’ maximal ability to consume fat does not limit MFO during two-legged exercise per se. Finally, in ‘The Timing of Thigh Muscle Activity is a Factor Limiting Performance in the Deceleration Phase of the 100-m Dash’, Kakehata et al. investigated thigh muscle activity using electromyography (rectus femoris: RF and biceps femoris: BF) in both legs to clarify why deceleration occurs in the 100-m dash. The authors found that deceleration was associated with decreased step frequency. RF and BF timings were delayed in the running cycle in the deceleration phase (80-100 m) compared to the maximal speed phase (50-70 m) and inter-leg muscular coordination, specifically the timing of the swing leg (RF) relative to the grounded leg (BF), was also altered. These results suggest the importance of considering the inter-leg thigh muscular coordination in the determination of 100-m running performance.
Andrew M. Jones
University of Exeter