BACKGROUND: the magnitude of cardiovascular responses is dependent on the static and dynamic components as well as the duration and intensity of the contraction performed. OBJECTIVE: to evaluate the heart rate responses to different percentages of isometric contractions in 12 patients (63 ± 11.6 years) with coronary artery disease and/or risk factors for coronary artery disease that were participating in a phase III cardiac rehabilitation program. METHODS: heart rate variation (ΔHR) was evaluated during maximum (MVC, five and ten seconds in duration) and submaximal (SMVC, 30 and 60% of MVC-5, until muscle exhaustion) voluntary contraction, using a handgrip dynamometer. Additionally, the representative index of cardiac vagal modulation (RMSSD index) was calculated at rest (pre-contraction), at the final 30 seconds of SMVC and during recovery (post-contraction). RESULTS: ΔHR showed higher values in MVC-10 versus MVC-5 (17 ± 5.5 vs 12 ± 4.2 bpm, p<0.05) and the SMVC-60 vs SMVC-30 (19 ± 5.8 vs 15 ± 5.1 bpm, p<0.05). However, results for CVM-10 showed similar ΔHR compared to results for CVSM (p> 0.05). RICVM at rest decreased (p<0.05) during SMVC-30 (30% = 27.9 ± 17.1 vs 12.9 ± 8.5 ms) and SMVC-60 (60% =25.8 ± 18.2 vs 9.96 ± 4.2 ms), but returned to the baseline values when the contraction was interrupted. CONCLUSIONS: in patients with coronary artery disease and/or risk factors for coronary heart disease, low intensity isometric contraction, maintained over long periods of time, presents the same effect on the responses of HR, compared to a high intensity or maximal isometric contraction of briefly duration.
BACKGROUND: the magnitude of cardiovascular responses is dependent on the static and dynamic components as well as the duration and intensity of the contraction performed. OBJECTIVE: to evaluate the heart rate responses to different percentages of isometric contractions in 12 patients (63 ± 11.6 years) with coronary artery disease and/or risk factors for coronary artery disease that were participating in a phase III cardiac rehabilitation program. METHODS: heart rate variation (ΔHR) was evaluated during maximum (MVC, five and ten seconds in duration) and submaximal (SMVC, 30 and 60% of MVC-5, until muscle exhaustion) voluntary contraction, using a handgrip dynamometer. Additionally, the representative index of cardiac vagal modulation (RMSSD index) was calculated at rest (pre-contraction), at the final 30 seconds of SMVC and during recovery (post-contraction). RESULTS: ΔHR showed higher values in MVC-10 versus MVC-5 (17 ± 5.5 vs 12 ± 4.2 bpm, p<0.05) and the SMVC-60 vs SMVC-30 (19 ± 5.8 vs 15 ± 5.1 bpm, p<0.05). However, results for CVM-10 showed similar ΔHR compared to results for CVSM (p> 0.05). RICVM at rest decreased (p<0.05) during SMVC-30 (30% = 27.9 ± 17.1 vs 12.9 ± 8.5 ms) and SMVC-60 (60% =25.8 ± 18.2 vs 9.96 ± 4.2 ms), but returned to the baseline values when the contraction was interrupted. CONCLUSIONS: in patients with coronary artery disease and/or risk factors for coronary heart disease, low intensity isometric contraction, maintained over long periods of time, presents the same effect on the responses of HR, compared to a high intensity or maximal isometric contraction of briefly duration.
Authors: Ana Márcia Dos Santos António; Marcelo Tavella Navega; Marco Aurélio Cardoso; Luiz Carlos Abreu; Vitor E Valenti Journal: Int Arch Med Date: 2014-09-23