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Objective: In type 1 diabetes, autonomic dysfunction may occur early as a decrease in heart rate variability (HRV). In populations without diabetes, the positive effects of exercise training on HRV are well-documented. However, exercise in individuals with type 1 diabetes, particularly if strenuous and prolonged, can lead to sharp glycemic variations, which can negatively impact HRV. This study explores the impact of a 9-day cycling tour on HRV in this population, with a focus on exercise-induced glycemic excursions.Research Design and Methods: Twenty amateur athletes with uncomplicated type 1 diabetes cycled 1,500 km. HRV and glycemic variability were measured by heart rate and continuous glucose monitoring. Linear mixed models were used to test the effects of exercise on HRV, with concomitant glycemic excursions and subject characteristics considered as covariates.Results: Nighttime HRV tended to decrease with the daily distance traveled. The more time the subjects spent in hyperglycemia, the lower the parasympathetic tone was. This result is striking given that hyperglycemic excursions progressively increased throughout the 9 days of the tour, and to a greater degree on the days a longer distance was traveled, while time spent in hypoglycemia surprisingly decreased. This phenomenon occurred despite no changes in insulin administration and a decrease in carbohydrate intake from snacks.Conclusions: In sports enthusiasts with type 1 diabetes, multiday prolonged exercise at moderate-to-vigorous intensity worsened hyperglycemia, with hyperglycemia negatively associated with parasympathetic cardiac tone. Considering the putative deleterious consequences on cardiac risks, future work should focus on understanding and managing exercise-induced hyperglycemia. [ABSTRACT FROM AUTHOR]

Objective: To analyze the consequences on heart rate variability (HRV) of a hospitalization period due to surgery of the knee in sportsmen. Patients: Ten soccer players who had undergone knee surgery took part in this study. Design: HRV was measured before and after hospitalization within a 7-day interval. Results: After the hospitalization phase, heart rate at rest increased significantly (3 beats/minute). A significant decrease of 7% in the cardiac inter beat interval (R-R interval), P < 0.05 and a 66% decrease in total power spectral density: -66%, P < 0.05 were observed. The disturbance of the autonomic nervous system could be due to a variation in cardiac vagal activity resulting in a 64% decrease in the high frequencies (P < 0.05). This variation was not associated with a modification in normalized markers (LFn.u., HFn.u.) and LF/HF ratio (P > 0.05). Conclusion: In sportsmen, a hospitalization period led to an increase in resting heart rate and was associated with a disturbance of the autonomic nervous system. [ABSTRACT FROM AUTHOR]

A bioenergetical analysis of manoeuvrability and agility performance for wheelchair players is inexistent. It was aimed at comparing the physiological responses and performance obtained from the octagon multistage field test (MFT) and the modified condition in “8 form” (MFT-8). Sixteen trained wheelchair basketball players performed both tests in randomized condition. The levels performed (end-test score), peak values of oxygen uptake (VO2peak), minute ventilation (VEpeak), heart rate (HRpeak), peak and relative blood lactate (Δ[Lact−] = peak – rest values), and the perceived rating exertion (RPE) were measured. MFT-8 induced higher VO2peak and VEpeak values compared to MFT (VO2peak: 2.5 ± 0.6 versus 2.3 ± 0.6 L·min−1 and VEpeak: 96.3 ± 29.1 versus 86.6 ± 23.4 L·min−1; P<0.05) with no difference in other parameters. Significant relations between VEpeak and end-test score were correlated for both field tests (P<0.05). At exhaustion, MFT attained incompletely VO2peak and VEpeak. Among experienced wheelchair players, MFT-8 had no effect on test performance but generates higher physiological responses than MFT. It could be explained by demands of wheelchair skills occurring in 8 form during the modified condition. [ABSTRACT FROM AUTHOR]

This study aimed to compare the recovery kinetics of physical performance and subjective ratings in response to a soccer-specific exercise simulation on natural grass and artificial turf. Physical performance tests and subjective ratings were assessed on 13 professional soccer players before, immediately after, 24 h and 48 h after the test. Physical performance tests included squat jump, countermovement jump, 6-s sprint on a non-motorised treadmill and isokinetic eccentric hamstring assessment (2.09 rad · s−1). Hamstring peak torque decrement was higher (P < 0.05) on natural grass than on artificial turf immediately (-4.0%, CI 95%: -10.0 to 2.0%, Effect Size [ES] = 0.29), 24 h (-3.1%, CI 95%: -9.3 to 3.1%, ES = 0.29) and 48 h (-3.8%, CI 95%: -8.5 to 0.9%, ES = 0.43) after the test. Squat jump performance decrement was significantly lower (P < 0.05) on natural grass than artificial turf 48 h after the test (+3.7%, CI 95%: 1.1 to 6.3%, ES = 0.40). Sprint performance showed no change from baseline performance for both trials throughout the protocol. No significant interaction between surface and time was found for countermovement jump and subjective ratings. These results suggest that a one-off exercise on artificial turf does not induce greater fatigue nor does it delay the recovery process when compared to natural grass among regular artificial turf players. [ABSTRACT FROM PUBLISHER]

The article presents a study that compared the power outputs of the intermittent maximal lactate steady state (MLSSi) and the intermittent critical power (CPi), and also compared the perceptual and physiological responses of of people exercising at MLSSi and CPi. The test methodology involved intermittent trials performed by ten subjects on a cycle ergometer.

This study was designed to test the hypothesis that subjects having faster oxygen uptake (VO(2)) kinetics during off-transients to exercises of severe intensity would obtain the smallest decrement score during a repeated sprint test. Twelve male soccer players completed a graded test, two severe-intensity exercises, followed by 6 min of passive recovery, and a repeated sprint test, consisting of seven 30-m sprints alternating with 20 s of active recovery. The relative decrease in score during the repeated sprint test was positively correlated with time constants of the primary phase for the VO(2) off-kinetics (r = 0.85; p < 0.001) and negatively correlated with the VO(2) peak (r = -0.83; p < 0.001). These results strengthen the link found between VO(2) kinetics and the ability to maintain sprint performance during repeated sprints. [ABSTRACT FROM AUTHOR]

The aim of this article is to determine correspondences between three levels of continuous and intermittent exercise (CE and IE, respectively) in terms of steady-state oxygen uptake (VO(2SS)) and heart rate (HR) in children. Fourteen healthy children performed seven exercises on a treadmill: one graded test for the determination of maximal aerobic speed (MAS), three CE at 60, 70 and 80% of MAS (CE60, CE70 and CE80) and three IE (alternating 15 s of exercise intercepted with 15 s of passive recovery) at 90, 100 and 110% of MAS (IE90, IE100 and IE110). Mean VO(2SS) and mean HR were determined for both continuous and intermittent exercises. For comparison, three associations were designed: CE60 versus IE90, CE70 versus IE100 and CE80 versus IE110. No VO(2SS) difference was observed for CE60 versus IE90 and CE70 versus IE100 whereas a significant difference (P < 0.01) was found for CE80 versus IE110 (1.36 +/- 0.45 vs. 1.19 +/- 0.38 L min(-1), respectively). Significant linear regressions were found for the three CE versus IE associations for VO(2SS) (0.60 < r (2) < 0.99, P < 0.05). For the three associations, mean HR presented no significant difference. Only one significant relation was found for CE80 versus IE110 association (r(2) = 0.49, P < 0.05). Correspondences between CE and IE intensities are possible in terms of VO(2SS) whatever the level of exercise; even if for high intensities, VO(2SS) was higher during CE. These results demonstrated that it is possible to diversify the exercise modality while conserving exercise individualization. [ABSTRACT FROM AUTHOR]

The purpose of this study was to observe the effect of high intermittent exercise training on children's heart rate variability (HRV). Thirty-eight children (age 9.6 +/- 1.2 years) were divided into an intermittent (IT, n = 22) and a control group (CON, n = 16). At baseline and after a 7-week training period, HRV parameters, peak oxygen consumption (VO(2peak)) and maximal aerobic velocity (MAV) were assessed. Training consisted of three 30-min sessions composed by short maximal and supramaximal runs at velocities ranging from 100 up to 190% of MAV. HRV was computed in time and frequency domains. Training resulted in a significant increase in MAV and VO(2peak) in IT (P < 0.05) only without any significant change in HRV parameters for the two groups. Thus, 7 weeks of high intermittent exercise training allows to improve aerobic fitness. However, this modality of training was not sufficient enough to underline a possible effect on the heart rate autonomic regulation in children. [ABSTRACT FROM AUTHOR]

The aim of this study was to determine if subjects matched for VO2max but with differing aerobic endurance displayed similar heart rate variability (HRV) at rest and heart rate recovery (HRR) after maximal exercise. We hypothesized that the higher the aerobic endurance, the higher the HRV and the faster the HRR. Twenty-eight well trained middle- and long-distance runners (24 men and 4 women) performed a maximal continuous graded exercise test for the determination of maximal oxygen consumption (VO2max), ventilatory threshold (VT), peak treadmill velocity (PTV) and HRR, as well as a test to measure the autonomic regulation of heart rate during supine rest, using HRV analysis. Once both tests were completed, subjects were matched for VO2max and assigned to the low endurance or the high endurance group, depending on the %PTV at which VT occurred (81.9 +/- 2.9 and 88.3 +/- 3.1%PTV for both groups, respectively; P < 0.0001). Contrary to our hypotheses, neither HRV nor HRR parameters were different between groups or associated with aerobic endurance. VO2max (59.0+/-7.3 ml min(-1) kg(-1)) was inversely correlated with ln SDNN (r = -0.44, P < 0.05), ln HF (r = -0.52, P < 0.05), ln LF + HF (r = -0.53, P < 0.05). These results suggest that aerobic endurance is not associated with cardiovascular autonomic control, as measured by HRV and HRR. [ABSTRACT FROM AUTHOR]

The aim of this study was to analyze the effects of recovery mode (active/passive) on time spent at high percentage of maximal oxygen uptake (VO2max) i.e. above 90% of VO2max (t90VO2max) and above 95% of VO2max (t95VO2max) during a single short intermittent session. Eight endurance-trained male adolescents (15.9 +/- 1.4 years) performed three field tests until exhaustion: a graded test to determine their VO2max (57.4 +/- 6.1 ml min(-1) kg(-1)), and maximal aerobic velocity (MAV; 17.9 +/- 0.4 km h(-1)), and in a random order, two intermittent exercises consisting of repeated 30 s runs at 105% of MAV alternated with 30 s passive (IE(P)) or active recovery (IE(A), 50% of MAV). Time to exhaustion (t(lim)) was significantly longer for IE(P) than for IE(A) (2145 +/- 829 vs. 1072 +/- 388 s, P < 0.01). No difference was found in t90VO2max and t95VO2max between IE(P) (548 +/- 499-316 +/- 360 s) and IE(A) (746 +/- 417-459 +/- 332 s). However, when expressed as a percentage of t(lim), t90VO2max and t95VO2max were significantly longer (P < 0.001 and P < 0.05, respectively) during IE(A) (67.7 +/- 19%-42.1 +/- 27%) than during IE(P) (24.2 +/- 19%-13.8 +/- 15%). Our results demonstrated no influence of recovery mode on absolute t90VO2max or t95VO2max mean values despite significantly longer t(lim) values for IE(P) than for IE(A). In conclusion, passive recovery allows a longer running time (t(lim)) for a similar time spent at a high percentage of VO2max. [ABSTRACT FROM AUTHOR]

The article presents a study which was conducted to compare R-R intervals and the subsequent analysis of heart rate variability obtained from the Polar S810 heart rate monitor (HRM) with an electrocardiogram (ECG) during an orthostatic test. Healthy subjects performed an active orthostatic test during which R-R intervals were simultaneously recorded with the HRM and ECG recorder. The intervals were significantly different in the supine and standing position between the ECG and the HRM uncorrected and corrected signal.