The interactive effects of age and sex on the neuro-cardiovascular responses during fatiguing rhythmic handgrip exercise

The impact of age on exercise pressor responses is equivocal, likely because of sex-specific neuro-cardiovascular changes with age. However, assessments of the interactive effects of age and sex on muscle sympathetic nerve activity (MSNA) responses to exercise are lacking. We tested the hypothesis that older females would exhibit exaggerated increases in blood pressure (BP) and MSNA discharge patterns during handgrip exercise compared with similarly aged males and young adults. Twenty-five young (25 (2) years; mean (SD)) males (YM; n = 12) and females (YF; n = 13) and 23 older (71 (5) years) males (OM; n = 11) and females (OF; n = 12) underwent assessments of BP, total peripheral resistance (TPR; Modelflow) and MSNA action potential (AP) discharge patterns (microneurography) during incremental rhythmic handgrip exercise and post-exercise circulatory occlusion (PECO). OM demonstrated larger ?BP and ?TPR from baseline than YM (both P < 0.001) despite smaller increases in ?APs/burst (OM: 0.4 (3) vs. YM: 5 (3) spikes/burst, P < 0.001) and ?AP clusters/burst (OM: 0.1 (1) vs. YM: 1.8 (1) clusters/burst, P < 0.001) during exercise. Testosterone was lower in OM than YM (P < 0.001) and was inversely related to ?BP but positively related to ?AP clusters/burst in males (both P = 0.03). Conversely, YF and OF demonstrated similar ?BP and ?AP discharge during exercise (range: P = 0.75-0.96). Age and sex did not impact haemodynamics or AP discharge during PECO (range: P = 0.08-0.94). Altogether, age-related changes in neuro-cardiovascular reactivity exist in males but not females during fatiguing exercise and seem to be related to testosterone. This sex-specific impact of age underscores the importance of considering biological sex when assessing age-related changes in neuro-cardiovascular control during exercise.

Automated summary

The impact of age on exercise pressor responses differs between males and females. Older males exhibit larger increases in blood pressure and total peripheral resistance during handgrip exercise compared to younger males. However, age does not have a significant effect on these responses in females. Testosterone levels play a role in the observed sex-specific differences. These findings highlight the importance of considering biological sex when studying age-related changes in neuro-cardiovascular control during exercise.