Hemodynamic responses during lower-limb resistance exercise with blood flow restriction in healthy subjects.

AIM: The purpose of this study was to compare hemodynamic responses during low-intensity resistance exercise, with (LI-BFR) and without (LI) blood flow restriction, with high-intensity resistance exercise (HI). METHODS: In a randomized crossover design, 17 healthy subjects performed 3 sets (15 repetitions, 20% 1RM, 45-second rest interval between sets) of 45° bilateral leg press exercises for the LI-BFR and LI protocols; and 3 sets (8 repetitions; 80% 1RM; 1-minute rest interval between sets) for the HI protocol. The BFR was established using two sphygmomanometers (18x90 cm) inflated to partially occlude blood flow to the femoral artery. Systolic blood pressure (SBP), diastolic blood pressure (DBP), heart rate (HR), stroke volume (SV), cardiac output (CO) and total peripheral resistance (TPR) were evaluated continuously and noninvasively by beat-to-beat measurements during each protocol. RESULTS: Significantly smaller values were demonstrated during the LI-BFR session versus the HI session between the first and second sets for SBP; during the first, second and third sets for DBP; during the first set for HR; during the first, second and third sets for SV; during the first set for CO, and during the second set for TPR. Conversely, perceived exertion was significantly higher in the LI-BFR session versus the HI session. CONCLUSION: The LI-BFR session was associated with significantly reduced cardiovascular responses versus the HI session, but showed higher values of subjective perceived exertion.

Cardiovascular adaptations to resistance training in elderly postmenopausal women.

The purpose of this study was to investigate the effect of resistance training on resting blood pressure and heart rate variability in elderly postmenopausal women. 29 untrained, non-hypertensive elderly women were randomly assigned to 2 groups: an intervention group (n=15, 65.5±5.0 years, 57.3±6.5 kg, 156.7±5.1 cm) that underwent a supervised resistance training program (8 exercises, 2 sets, 10-15 repetitions, 3 times/week) or a control group (n=14, 66.2±4.1 years, 61.1±11.7 kg, 157.5±7.1 cm) that participated in a supervised stretching program (25-30 min/session, 2 times/week). Resting auscultatory blood pressure, heart rate variability, evaluated from short recordings in a seated position, and maximal dynamic strength (1-RM test) were measured at baseline and after 12 weeks. A group x time ANOVA revealed that muscular strength increased significantly in the resistance training group (+ 10.2% for bench press and +12.7% for leg extension, P<0.05). Systolic blood pressure was reduced significantly in the resistance training group from pre- to post-intervention period (- 5 mmHg; P<0.05), while no significant effect was noted for diastolic blood pressure and heart rate variability indexes (P>0.05). None of these variables changed in the control group throughout the study. In conclusion, a supervised resistance training program improved muscular strength and reduced systolic blood pressure without affecting diastolic blood pressure and heart rate variability in elderly postmenopausal women.

Cardiac autonomic responses to repeated shuttle sprints.

Team sport match play requires athletes to perform a number of repeated shuttle sprints. However, the acute effects of these repeated sprint sequences on lactic acidosis and resulting autonomic state perturbation are not known. The aim of this study was to observe and compare the blood lactate and post-exercise cardiac autonomic responses of a repeated shuttle-sprint ability test with the 30-15 Intermittent Fitness Test (30-15 (IFT)); the latter test representing a standard for exhaustive supramaximal effort. Thirteen adult team sport players performed the repeated shuttle-sprint ability test and the 30-15 (IFT) on separate days in a counter-balanced order. The repeated shuttle-sprint ability test consisted of six repetitions of maximal 2x15 m shuttle sprints ( approximately 5 s) departing every 20 s, while the 30-15 (IFT) involved progressive 30 s shuttle runs interspersed with 15 s of passive recovery until exhaustion. Blood lactate was measured before and after the tests, while autonomic responses were assessed using immediate heart rate recovery and heart rate variability indices. Peak blood lactate (10.6+/-2.1 vs. 10.2+/-2.8 mM) and heart beats recovered in one minute after exercise cessation (36.4+/-7.8 vs. 39.3+/-7.9 bpm) were similar after both the repeated shuttle-sprint ability test and the 30-15 (IFT). With the exception of the vagal-related time-varying root mean square of successive R-R interval differences at each 30 s, which recovered earlier after the repeated shuttle-sprint ability test compared with 30-15 (IFT), all heart rate variability indices decreased similarly after both tests in comparison to baseline values. In conclusion, the repeated shuttle-sprint ability test was shown to induce comparable levels of lactic acidosis and post-exercise autonomic state as the 30-15 (IFT). These levels of metabolic and autonomic states are likely to occur during team sport match play.