The Effects of Long-Lasting Exercise Involvement on the Physiological Profile of Moderately Active Women of Varying Age

Background: To explore the rate of adjustment of the exercising muscle oxidative metabolism – the on-transient exercise model widely used in general, clinical and aging populations. Although a large number of studies using a step-transition exercise model were performed on men, less is known regarding changes in the rate of muscle oxidative metabolism for the active female population, in part due to the technical limitations of measuring near infrared spectroscopy (NIRS) in ageing women. Moreover, data on the cardiovascular response during on-transient exercise in women are also sparse, and this is especially important since the previous work of Hart et al. (2009) showed sex specifics in both blood pressure regulation and muscle sympathetic nerve activity. Taken together, the application of the above-mentioned integrative model, combined with tensiomyography (TMG) evaluation, could provide a more comprehensive insight into the prognostic role of different factors attributed to the cardiopulmonary exercise testing (CPET) performance in women.

Aim: We studied the effects of age on different physiological parameters, including those derived from the i) maximal (CPET), ii) moderate-intensity step-transitions, and iii) (TMG)-derived variables, in moderately active women of varying age.

Methods: Twenty-eight women (age range from 19 to 53 y), completed three laboratory visits, including baseline data collection, TMG assessment, V̇O2 max test via CPET, and a step-transition test from 20 W to a moderate-intensity cycling power output (PO), corresponding to V̇O2 at a 90% gas exchange threshold. Following preliminary measurements, these women were then divided into young (age range 19-30 y) and middle-aged (age range 36-53 y) groups. During the step-transitions breath-by-breath pulmonary oxygen uptake (V̇O2p), near infrared spectroscopy derived muscle deoxygenation (ΔHHb), and beat-by-beat cardiovascular response (Finapres) were continuously monitored.

Results: There were no differences observed between the young and middle-aged women in their V̇O2 max and peak PO, while the HR max was 12 bpm lower in middle-aged compared to young women (p=.016). In addition, no differences were observed between the age groups in τV̇O2p, ΔHHb, and τHR during on-transients. The first regression model showed that age did not attenuate the maximal CPET capacity in the studied population (p=.638), while in the second model a faster τV̇O2p, combined with shorter TMG-derived contraction time (Tc) of the vastus lateralis (VL) were associated with a higher V̇O2 max (~30% of explained variance, p=.039).

Conclusion: We found that long-lasting exercise involvement protects against V̇O2 max and τV̇O2p deterioration in moderately active women. More specifically, no differences between age groups were found in τV̇O2p, τΔHHb, τHR, during on-transients, while faster pulmonary τV̇O2p and shorter contraction time (Tc) of the VL explain 33% of the variance in superior V̇O2 max attainment.