Table 2. Mean and standard deviation of HRV indexes and blood pressure (BP) at baseline before and after 8-weeks of HIIE plus strength exercise. Variables HSG (n = 11) CG (n = 10) Mean RR Pre 907.9 ± 106.4 969.3 ± 159.4 Post 978.8 ± 115.7 * 937.7 ± 129.2 Mean HR (beat/min) Pre 67.3 ± 7.5 63.8 ± 9.6 Post 62.5 ± 7.5 * 65.5 ± 8.4 SDNN (ms) Pre 71.3 ± 26.9 82.0 ± 33.6 Post 79.6 ± 21.5 80.8 ± 29.0 RMSSD (ms) Pre 41.4 ± 20.4 62.4 ± 26.7 Post 47.4 ± 17.6 57.6 ± 25.0 LF (nu) Pre 62.5 ± 15.6 †  46.9 ± 11.4 Post 64.5 ± 10.1 †  53.4 ± 15.5 HF (nu) Pre 37.4 ± 15.6 †  52.9 ± 11.4 Post 35.4 ± 10.1 †  46.5 ± 15.5 LF (ms²) Pre 1023.1 ± 821.7 1261.8 ± 881.1 Post 1396.6 ± 942.8 1046.4 ± 899.6 HF (ms²) Pre 743.9 ± 937.2 1063.6 ± 744.2 Post 788.1 ± 615.9 1182.2 ± 728.1 LF/HF Pre 1.3 ± 0.8 1.1 ± 1.1 Post 1.7 ± 1.5 0.8 ± 1.2 SBP (mmHg) Pre 122.8 ± 11.3 124.9 ± 6.8 Post 118.7 ± 9.4 125.2 ± 5.9 DBP (mmHg) Pre 62.3 ± 5.6 65.0 ± 6.6 Post 62.9 ± 5.4 67.1 ± 5.8 Mean ± standard deviation. Mean HR = mean hear rate; Mean RR = mean RR intervals; SDNN = standard deviation of all normal RR intervals written in milliseconds; RMSSD = square root of the square mean of the differences of the adjacent normal RR intervals, in milliseconds; LF ms² = low-frequency component in milliseconds squared; LF nu = low frequency component in unit of measurement; HF ms² = high-frequency component in milliseconds squared; HF nu = high-frequency component in unit of measurement; LF/HF = balance between the low and high frequency component; beat/min = beat per minute; SBP = systolic blood pressure; DBP = diastolic blood pressure; mmHg = millimetres of mercury; HSG = high intensity aerobic exercise combined strength group; CG = control group; Pre = pre-training; Post = post-training; * = significant difference compared with the pre-training moment (p < 0.05); †  = significant difference compared with the control group (p < 0.05).