AIM: The study assessed the effects of different weekly training frequencies performed over a 12 week exercise programme (strength, endurance, balance) on autonomic cardiac activity, blood pressure and cardiorespiratory fitness (CRF) in elderly individuals. METHODS: Fifty-eight individuals participated in the study: 2TG (N=24, 71.1±6.4 yrs; 19 females, 5 males) performing two, 60min sessions/week; and 3TG (N=34, 72.3±7.9 yrs; 25 females, 9 males) performing three, 60min sessions/week. Time domain and spectral analysis of heart rate variability (HRV) quantified autonomic cardiac regulation. RESULTS: Natural logarithm (Ln) transformation was applied to all HRV parameters. There were significant reductions in total power (Ln TP) (p=0.006), low frequency (Ln LF) (p=0.013), high frequency (Ln HF) (p=0.013) and root mean square of successive differences (Ln rMSSD) (p=0.014) post training in 3TG after intervention. Diastolic BP (DBP) decreased significantly in both groups (2TG: P<0.001; 3TG: P<0.001). Both groups showed significant improvements in six-minute walk distance (2TG: P=0.003, 3TG: P=0.001). However, there were significant HRV differences between 2TG and 3TG for Ln TP (P=0.018), Ln LF (P=0.049), Ln HF (P=0.039) and Ln rMSSD (P=0.049). CONCLUSIONS: A combined exercise programme resulted in improved DBP and CRF irrespective of training two or three 60min sessions/week. However, training three, sessions/week induced negative health-related changes in autonomic cardiac activity through reducing HRV parasympathetic function, while HRV was maintained in the group training twice a week.

Discipline of Biokinetics Exercise and Leisure Sciences School of Health Sciences University of KwaZulu Natal Durban South Africa

Discipline of Biokinetics Exercise and Leisure Sciences School of Health Sciences University of KwaZulu Natal Durban South Africa; AFC Bournemouth Bournemouth United Kingdom

Discipline of Biokinetics Exercise and Leisure Sciences School of Health Sciences University of KwaZulu Natal Durban South Africa; Discipline of Sport and Exercise Science UC Research Institute for Sport and Exercise Faculty of Health University of Canberra ACT Australia

Faculty of Physical Culture Palacký University Olomouc Czech Republic

School of Clinical Medicine University of KwaZulu Natal Durban South Africa

Stabilization period before capturing an ultra-short vagal index can be shortened to 60 s in endurance athletes and to 90 s in university students