The effect of short and long term endurance training on systemic, and muscle and prefrontal cortex tissue oxygen utilisation in 40 – 60 year old women

Purpose: Aerobic endurance training (ET) increases systemic and peripheral oxygen utilisation, and the time course of these adaptations is not linear. However, the timing and mechanisms of increases, or plateau, in oxygen utilisation, as a function of increased training years beyond one year are not known. This study tested the hypothesis that in women aged 40 - 60 years performing the same current training load; systemic O2 utilisation (VO2) and tissue oxygenation (HHb) at the Vastus Lateralis (VL) and Gastrocnemius (GAST) would be higher in long term trained (LTT; > 5 yr) compared to a short term trained (STT; 6 - 24 months) participants during ramp incremental (RI) cycling exercise, but similar during square-wave constant load (SWCL) cycling exercise performed at the same relative exercise intensity (below ventilatory turn point [VTP]); and secondly that pre-frontal cortex (PFC) HHb would be similar between groups during both conditions. Methods: Thirteen STT and 13 LTT ET participants performed RI and SWCL conditions on separate days. Simultaneous measures of VO2, and VL, GAST, and PFC HHb were conducted. Results: VO2peak was 19% higher in LTT compared to STT, and VO2 was higher in LTT at each of the relative intensities of 25%, 80% and 90% of VTP during the SWCL condition. HHb at the VL was significantly higher in LTT compared to STT at peak exercise (4.54 vs 1.55 μMol/l), and at 25% (0.99 vs 0.04 μMol/l), 80% (3.19 vs 1.14 μMol/l) and 90% (4.62 vs 2.07 μMol/l) of VTP during SWCL. Conclusions: The additional (12.9 ± 9.3) years of ET in the LTT, resulted in higher VO2, and HHB at the VL at peak exercise, and sub- VTP exercise. This indicates that in women 40 - 60 years, systemic and muscle O2 utilisation continues to improve with prolonged regular ET beyond two years.