Introduction

How ageing, exercise and disease effect neuromuscular function in adults is complex. The aim of this study was to gain greater insight into this relationship by undertaking a nine-year longitudinal study in a cohort of physiologically defined, highly-active, older cyclists. 

 

Methods

Eighty-two older road cyclists now aged 72.4±5.9 years, were re-tested after nine years¹. On their return, we observed that not all met the original health criteria. Based on their deviation from the original health criteria we re-categorised cyclists in to three groups; i) no declared health issues (Group 1, n=23 males, n= 12  females), ii) exhibiting new but well-controlled health condition(s) unlikely to affect exercise (Group 2, n=14 males, n=10 females and iii) having any poorly controlled underlying condition(s) that had the potential to compromise exercise capacity (Group 3, n=16 males, n= 7 females). We assessed maximum isometric strength of knee extensors (MVT), peak power during explosive cycling (PP), grip strength, and measured time up and go (TUG). DXA scanning determined lower limb fat free mass (LLFFM). In addition, we measured voluntary activation (neural drive) during MVT (MVTVA) through the twitch interpolation method, peroneal nerve conduction velocity (NCV), motoneuron excitability (H-reflex; ratio of H-max to M-max), as well as one-leg balance using the preferred leg in eyes open (B_EO) and eyes closed (B_EC) conditions. Statistical analysis: i) paired t-test to assess overall change with time and ii) multiple regression analysis for between-group interaction over time. Data are presented as mean±SD.

 

Results

All n=82 participants were still cycling now aged 72.4±5.9 years, height (m; 1.7±0.1), and body mass (kg; 68.7±10.7). Data from pre and post nine years showed a decline in self-reported cycling volume (km month⁻¹; 667.7±312.5 vs. 456.2±301.8; p<0.001). MVT (N.m; 160.2±43.4 vs. 149.4±38.8; p = 0.006), and PP (W; 964.4±180.5 vs. 909.3±203.5; p < 0.001) both declined with time. LLFFM (kg) declined from 17.6±3.3 to 15.8±3.4. When MVT was normalised to LLFM there was no age effect (N.m.kg.FFM^-1; 9.1±1.9 vs. 9.6±2.3; p = 0.07), but a decline remained in PP (W.kg.FFM^-1; 55.0±5.8 vs. 58.2±10.4; p = 0.002). Grip strength declined significantly over time (N; 408.5±97.3 vs. 373.3±103.9; p < 0.001), while TUG (s; 5.6±0.8 vs. 5.2±0.9; p < 0.001) improved. With respect to neural function, MVTVA (%; 93.3±6.2 vs. 89.2±6.3; p < 0.001), the H-reflex (%; 0.35±0.24 vs. 0.26±0.20; p < 0.001), NCV (ms^-1; 43.9±5.3 vs. 40.2±9.4; p = 0.001) and BEC (s; 6.4±2.9 vs. 5.1±2.7) all declined significantly over time. There was no change in B_EO sway over time in either the anteroposterior (mm; 6.4±2.0 vs. 6.2±1.9; p = 0.52) or mediolateral (mm; 5.6±1.3 vs. 5.7±1.5; p = 0.15) directions. Importantly, the multiple regression analysis revealed no effect of change in health status (i.e. between the three groups) in any of the indices measured after nine years. 

 

Conclusions:

Whilst neuromuscular function declined after nine years of active ageing, we were unable to differentiate between the three different health groups defined above. This suggests that exercise has a positive effect in maintaining neuromuscular function across a wide variety of ageing phenotypes.