Muscle Oxygenation, Neural, and Cardiovascular Responses to Isometric and Workload-matched Dynamic Resistance Exercise

Abstract

Differences in blood flow patterns and energy cost between isometric and dynamic resistance exercise may result to variant cardiovascular, neural, and muscle metabolic responses. We aimed to compare the cardiovascular, baroreceptor sensitivity, and muscle oxygenation responses between workload-matched, large muscle-mass isometric and dynamic resistance exercises. Twenty-four young men performed an isometric and a dynamic double leg-press protocol (4 sets×2 min) with similar tension time index (workload). Beat-by-beat hemodynamics, baroreceptor sensitivity, muscle oxygenation, and blood lactate were assessed. The increase in blood pressure was greater (p<0.05) in the 1st set during dynamic than isometric exercise (by ~4.5 mmHg), not different in the 2nd and 3rd sets, and greater in the 4th set during isometric exercise (by ~5 mmHg). Dynamic resistance exercise evoked a greater increase in heart rate, stroke volume, cardiac output, and contractility index (p<0.05), and a greater decline in peripheral resistance, baroreceptor sensitivity, and cardiac function indices than isometric exercise (p<0.05). Participants exhibited a greater reduction in muscle oxyhemoglobin and a greater increase in muscle deoxyhemoglobin in dynamic versus isometric exercise (p<0.001–0.05), with no differences in total hemoglobin and blood lactate. In conclusion, large muscle-mass, multiple-set isometric exercise elicits a relatively similar blood pressure but blunted cardiovascular and baroreceptor sensitivity responses compared to workload-matched dynamic resistance exercise. Differences in blood pressure responses between protocols appear small (~5 mmHg) and are affected by the number of sets. The muscle oxidative stimulus is greater during dynamic resistance exercise than workload-matched isometric exercise.

Comparing the effects of dynamic and holding isometric contractions on cardiovascular, perceptual, and near-infrared spectroscopy parameters: A pilot study

“…The different blood flow patterns between modes of contractions, the higher oxygen consumption, and the lower peripheral resistance with dynamic contractions are some of the factors that influence blood pressure response [ 50 ] presenting higher values in dynamic contractions in our study. RPP, also known as double product, was lower during ISO in consonance with previous studies [ 46 ] implying less myocardial effort and oxygen consumption.…”

“…This means that after an intervention program, the increase in deoxygenation is a favourable indicator. Only two studies compared this variable with the increment of dynamic and isometric contractions, using an equivalent load, and one of the studies did not show differences [ 36 ] while the other did [ 46 ], the latter corroborated by the results obtained in this study.…”

“…Concerning cardiovascular responses, namely, HR, there were higher values with the implementation of the DYN, as well as described elsewhere [ 46 ]. The higher values of HR evidenced during dynamic contractions may be explained by the higher cost of muscle activation and energy requirements [ 48 , 49 ].…”

“…Regarding tHb, it is important to know that it is not a valid indicator for assessing blood flow and its interpretation should be done carefully [ 12 ]. In a previous study [ 46 ], no significant differences were also observed between types of muscle contraction.…”

Comparison of Isometric and Dynamic Bridging Exercises on Low Back Muscle Oxygenation

“…A previous study evaluated the intramuscular pressure at different contraction levels to understand the capillary blood flow and tissue oxygenation and showed reduced oxygenation of lumbar paraspinal muscle at initial isometric contraction [14]. Current literature has shown a more significant decrease in oxyhemoglobin levels but an increase in deoxyhemoglobin when performing dynamic workload-matched leg-press exercise compared to isometric exercise [15]. An increase in muscle deoxygenation is essential as it determines vascular and muscular mitochondrial adaptations.…”