The acute cardiovascular and respiratory responses to isotonic versus isometric whole body resistance exercises

Purpose - Aerobic exercise is recommended for blood pressure control rather than resistance exercise. However, resistance exercise is gaining prominence, particularly isometric exercise. The purpose was to compare the cardiorespiratory responses to whole body isotonic (IT) and isometric (IM) resistance exercises.

Methods - 8 normotensive males (21 ± 2 years) completed one familiarisation session, then an IM and IT session in a counter-balanced order, each separated by at least 72 hours. 10-repetition maximum (10-RM) for each exercise was determined in the familarisation session. IM were held in the mid-range for 40 seconds and IT were performed for 10 repetitions with 2 seconds concentric and 2 seconds eccentric. Single sets of dumbbell lunge, barbell bench press, barbell squat, bent-over barbell row, and dumbbell shoulder press were performed, with 150 seconds rest between exercises. Oxygen uptake (V ̇O2) was collected continuously. Blood pressure (BP) and heart rate (HR) were recorded post-exercise. Rate-pressure product (RPP) was calculated from HR and BP. Energy expenditure (EE) was calculated from V ̇O2. Repeated measures analyses were applied to the data.

Results - Mean EE was significantly greater during IT (6.14 ± 0.65 kcal) than IM (4.52 ± 0.73 kcal; p=0.024), with EE greater during IT compared to IM for lunge (6.86 ± 1.55 v 4.98 ± 0.92 kcal; p=0.033), squat (8.32 ± 1.80 v 4.54 ± 1.14 kcal; p=0.002), and row (6.66 ± 0.82 v 5.36 ± 0.77 kcal; p=0.001). Mean systolic BP (137 ± 12 v 134 ± 11 mmHg; p=0.609) and diastolic BP (73 ± 13 v 73 ± 4 mmHg; p=0.923) were not significantly different between IT and IM for the five exercises. Mean RPP was not significantly different between IT (18086 ± 2764) and IM (16879 ± 2386; p=0.300), but was significantly greater during squat in IM (18668 ± 2217) and IT (20080 ± 4017) compared to bench press in IM (15023 ± 2324; p=0.025) and IT (15858 ± 2379; p=0.003). Systolic BP was not significantly reduced 60 minutes following IT (-8 ± 9 mmHg; p=0.053) and IM (-10 ± 15 mmHg; p=1.05) or diastolic BP (-0 ± 9 mmHg; p=1.000) following IT, however diastolic BP significantly reduced following IM (-10 ± 11 mmHg; p=0.028).

Conclusion - An IT resistance exercise session induced significantly greater energy expenditure while an IM resistance exercise session induced significantly greater post-exercise diastolic hypotension.