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Nocturnal Heart Rate Variability Following Supramaximal Intermittent Exercise

Al Haddad Hani, Paul B. Laursen, Ahmaidi Said, and Buchheit Martin

Purpose:

To assess the effect of supramaximal intermittent exercise on long-term cardiac autonomic activity, inferred from heart rate variability (HRV).

Methods:

Eleven healthy males performed a series of two consecutive intermittent 15-s runs at 95% VIFT (i.e., speed reached at the end of the 30-15 Intermittent Fitness Test) interspersed with 15 s of active recovery at 45% VIFT until exhaustion. Beat-to-beat intervals were recorded during two consecutive nights (habituation night and 1st night) before, 10 min before and immediately after exercise, as well as 12 h (2nd night) and 36 h (3rd night) after supramaximal intermittent exercise. The HRV indices were calculated from the last 5 min of resting and recovery periods, and the first 10 min of the first estimated slow wave sleep period.

Results:

Immediate post-supramaximal exercise vagal-related HRV indices were significantly lower than immediate pre-supramaximal exercise values (P < .001). Most vagal-related indices were lower during the 2nd night compared with the 1st night (eg, mean RR intervals, P = .03). Compared with the 2nd night, vagal-related HRV indices were significantly higher during the 3rd night. Variables were not different between the 1st and 3rd nights; however, we noted a tendency (adjusted effect size, aES) for an increased normalized high-frequency component (P = .06 and aES = 0.70) and a tendency toward a decreased low-frequency component (P = .06 and aES = 0.74).

Conclusion:

Results confirm the strong influence of exercise intensity on short- and long-term post exercise heart rate variability recovery and might help explain the high efficiency of supramaximal training for enhancing indices of cardiorespiratory fitness.

Cover International Journal of Sports Physiology and Performance

In International Journal of Sports Physiology and Performance Volume 4 (2009): Issue 4 (Dec 2009)

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Reliability of Physiological Attributes and Their Association With Stochastic Cycling Performance

Gregory T. Levin, Paul B. Laursen, and Chris R. Abbiss

Purpose:

To assess the reliability of a 5-min-stage graded exercise test (GXT) and determine the association between physiological attributes and performance over stochastic cycling trials of varying distance.

Methods:

Twenty-eight well-trained male cyclists performed 2 GXTs and either a 30-km (n = 17) or a 100-km stochastic cycling time trial (n = 9). Stochastic cycling trials included periods of high-intensity efforts for durations of 250 m, 1 km, or 4 km depending on the test being performing.

Results:

Maximal physiological attributes were found to be extremely reliable (maximal oxygen uptake [VO2max]: coefficient of variation [CV] 3.0%, intraclass correlation coefficient [ICC] .911; peak power output [PPO]: CV 3.0%, ICC .913), but a greater variability was found in ventilatory thresholds and economy. All physiological variables measured during the GXT, except economy at 200 W, were correlated with 30-km cycling performance. Power output during the 250-m and 1-km efforts of the 30-km trial were correlated with VO2max, PPO, and the power output at the second ventilatory threshold (r = .58–.82). PPO was the only physiological attributed measured during the GXT to be correlated with performance during the 100-km cycling trial (r = .64).

Conclusions:

Many physiological variables from a reliable GXT were associated with performance over shorter (30-km) but not longer (100-km) stochastic cycling trials.

Cover International Journal of Sports Physiology and Performance

In International Journal of Sports Physiology and Performance Volume 9 (2014): Issue 2 (Mar 2014)

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Day-to-Day Heart-Rate Variability Recordings in World-Champion Rowers: Appreciating Unique Athlete Characteristics

Daniel J. Plews, Paul B. Laursen, and Martin Buchheit

Purpose:

Heart-rate variability (HRV) is a popular tool for monitoring autonomic nervous system status and training adaptation in athletes. It is believed that increases in HRV indicate effective training adaptation, but these are not always apparent in elite athletes.

Methods:

Resting HRV was recorded in 4 elite rowers (rowers A, B, C, and D) over the 7-wk period before their success at the 2015 World Rowing Championships. The natural logarithm of the square root of the mean sum of the squared differences (Ln rMSSD) between R–R intervals, Ln rMSSD:R-R ratio trends, and the Ln-rMSSD–to–R-R-interval relationship were assessed for each championship-winning rower.

Results:

The time course of change in Ln rMSSD was athlete-dependent, with stagnation and decreases apparent. However, there were consistent substantial reductions in the Ln rMSSD:R-R ratio: rower A, baseline toward wk 5 (–2.35 ± 1.94); rower B, baseline to wk 4 and 5 (–0.41 ± 0.48 and –0.64 ± 0.65, respectively); rower C, baseline to wk 4 (–0.58 ± 0.66); and rower D, baseline to wk 4, 5, and 6 (–1.15 ± 0.91, –0.81 ± 0.74, and –1.43 ± 0.69, respectively).

Conclusions:

Reductions in Ln rMSSD concurrent with reductions in the Ln rMSSD:R-R ratio are indicative of parasympathetic saturation. Consequently, 3 of 4 rowers displayed substantial increases in parasympathetic activity despite having decreases in Ln rMSSD. These results confirm that a combination of indices should be used to monitor cardiac autonomic activity.

Cover International Journal of Sports Physiology and Performance

In International Journal of Sports Physiology and Performance Volume 12 (2017): Issue 5 (May 2017)

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Effect of ad Libitum Ice-Slurry and Cold-Fluid Ingestion on Cycling Time-Trial Performance in the Heat

Ed Maunder, Paul B. Laursen, and Andrew E. Kilding

Purpose:

To compare the physiological and performance effects of ad libitum cold-fluid (CF) and ice-slurry (IS) ingestion on cycling time-trial (TT) performance in the heat.

Methods:

Seven well-trained male triathletes and cyclists completed 2 maximaleffort 40-km cycling TTs in hot (35°C) and humid (60% relative humidity) conditions. In randomized order, participants ingested CF or IS (initial temperatures 4°C and –1°C, respectively) ad libitum during exercise. At each 5-km interval, time elapsed, power output, rectal and skin temperature, heart rate, and perceptual measures were recorded. The actual CF and IS temperatures during the 40-km TT were determined post hoc.

Results:

Performance time (2.5% ± 2.6%, ES = 0.27) and mean power (–2.2% ± 3.2%, ES = –0.15) were likely worse in the IS trial. Differences in thermoregulatory and cardiovascular measures were largely unclear between trials, while feeling state was worse in the later stages of the IS trial (ES = –0.31 to –0.95). Fluid-ingestion volume was very likely lower in the IS trial (–29.7% ± 19.4%, ES = –0.97). The temperatures of CF and IS increased by 0.37°C/min and 0.02°C/min, respectively, over the mean TT duration.

Conclusions:

Ad libitum ingestion of CF resulted in improved 40-km cycling TT performance compared with IS. Participants chose greater fluid-ingestion rates in the CF trial than in the IS trial and had improved feeling state. These findings suggest that ad libitum CF ingestion is preferable to IS during cycling TTs under conditions of environmental heat stress.

Cover International Journal of Sports Physiology and Performance

In International Journal of Sports Physiology and Performance Volume 12 (2017): Issue 1 (Jan 2017)

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Evaluating Training Adaptation With Heart-Rate Measures: A Methodological Comparison

Daniel J. Plews, Paul B. Laursen, Andrew E. Kilding, and Martin Buchheit

The aim of this study was to compare 2 different methodological assessments when analyzing the relationship between performance and heart-rate (HR) -derived indices (resting HR [RHR] and HR variability [HRV]) to evaluate positive adaptation to training. The relative change in estimated maximum aerobic speed (MAS) and 10-km-running performance was correlated to the relative change in RHR and the natural logarithm of the square root of the mean sum of the squared differences between R-R intervals on an isolated day (RHRday; Ln rMSSDday) or when averaged over 1 wk (RHRweek; Ln rMSSDweek) in 10 runners who responded to a 9-wk training intervention. Moderate and small correlations existed between changes in MAS and 10-km-running performance and RHRday (r = .35, 90%CI [–.35, .76] and r = –.21 [–.68, .39]), compared with large and very large correlations for RHRweek (r = –.62 [–.87, –.11] and r = .73 [.30, .91]). While a trivial correlation was observed for MAS vs Ln rMSSDday (r = –.06 [–.59, .51]), a very large correlation existed with Ln rMSSDweek (r = .72 [.28, .91]). Similarly, changes in 10-km-running performance revealed a small correlation with Ln rMSSDday (r = –.17 [–.66, .42]), vs a very large correlation for Ln rMSSDweek (r = –.76 [–.92, –.36]). In conclusion, the averaging of RHR and HRV values over a 1-wk period appears to be a superior method for evaluating positive adaption to training compared with assessing its value on a single isolated day.

Cover International Journal of Sports Physiology and Performance

In International Journal of Sports Physiology and Performance Volume 8 (2013): Issue 6 (Nov 2013)

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Heart-Rate Variability and Training-Intensity Distribution in Elite Rowers

Daniel J. Plews, Paul B. Laursen, Andrew E. Kilding, and Martin Buchheit

Purpose:

Elite endurance athletes may train in a polarized fashion, such that their training-intensity distribution preserves autonomic balance. However, field data supporting this are limited.

Methods:

The authors examined the relationship between heart-rate variability and training-intensity distribution in 9 elite rowers during the 26-wk build-up to the 2012 Olympic Games (2 won gold and 2 won bronze medals). Weekly averaged log-transformed square root of the mean sum of the squared differences between R-R intervals (Ln rMSSD) was examined, with respect to changes in total training time (TTT) and training time below the first lactate threshold (>LT1), above the second lactate threshold (LT2), and between LT1 and LT2 (LT1–LT2).

Results:

After substantial increases in training time in a particular training zone or load, standardized changes in Ln rMSSD were +0.13 (unclear) for TTT, +0.20 (51% chance increase) for time >LT1, –0.02 (trivial) for time LT1–LT2, and –0.20 (53% chance decrease) for time >LT2. Correlations (±90% confidence limits) for Ln rMSSD were small vs TTT (r = .37 ± .80), moderate vs time >LT1 (r = .43 ± .10), unclear vs LT1–LT2 (r = .01 ± .17), and small vs >LT2 (r = –.22 ± .50).

Conclusion:

These data provide supportive rationale for the polarized model of training, showing that training phases with increased time spent at high intensity suppress parasympathetic activity, while low-intensity training preserves and increases it. As such, periodized low-intensity training may be beneficial for optimal training programming.

Cover International Journal of Sports Physiology and Performance

In International Journal of Sports Physiology and Performance Volume 9 (2014): Issue 6 (Nov 2014)

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Hyperthermic Fatigue Precedes a Rapid Reduction in Serum Sodium in an Ironman Triathlete: A Case Report

Paul B. Laursen, Greig Watson, Chris R. Abbiss, Bradley A. Wall, and Kazunori Nosaka

Purpose:

To monitor the hydration, core temperature, and speed (pace) of a triathlete performing an Ironman triathlon.

Methods:

A 35-year-old experienced male triathlete participated in the Western Australian Ironman triathlon on December 1, 2006. The participant was monitored for blood Na+ concentration before the race (PRE), at the transitions (T1 and T2), halfway through the run (R21), and after the race (POST; 2hPOST). Core body temperature (T ; pill telemetry) was recorded continuously, and running speed (s3 stride sensor) was measured during the run.

Results:

The participant completed the race in 11 h 38 min, in hot conditions (26.6 ± 5.8°C; 42 ± 19% rel. humidity). His Tc increased from 37.0 to 38.6°C during the 57-min swim, and averaged 38.4°C during the 335-min bike (33.5 km·h-1). After running at 12.4 km·h-1 for 50 min in the heat (33.1°C), T increased to 39.4°C, before slowing to 10.0 km·h-1 for 20 min. T decreased to 38.9°C until he experienced severe leg cramps, after which speed diminished to 6 km·h-1 and T fell to 38.0°C. The athlete’s blood Na+ was constant from PRE to T2 (139-140 mEq·L-1, but fell to 131 mEq·L-1 at R21, 133 mEq·L-1 at POST, and 128 mEq·L-1at 2hPOST The athlete consumed 9.25 L of fuid from PRE to T2, 6.25 L from T2 to POST, and lost 2% of his body mass, indicating sweat losses greater than 15.5 L.

Conclusion:

This athlete slowed during the run phase following attainment of a critically high T and experienced an unusually rapid reduction in blood Na+ that preceded cramping, despite presenting with signs of dehydration.

Cover International Journal of Sports Physiology and Performance

In International Journal of Sports Physiology and Performance Volume 4 (2009): Issue 4 (Dec 2009)

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Carbohydrate Gel Ingestion and Immunoendocrine Responses to Cycling in Temperate and Hot Conditions

Jonathan Peake, Jeremiah J. Peiffer, Chris R. Abbiss, Kazunori Nosaka, Paul B. Laursen, and Katsuhiko Suzuki

Purpose:

Heat stress might attenuate the effects of carbohydrate on immunoendocrine responses to exercise by increasing endogenous glucose production and reducing the rate of exogenous carbohydrate oxidation. The authors compared the efficacy of carbohydrate consumption on immune responses to exercise in temperate vs. hot conditions.

Methods:

Ten male cyclists exercised on 2 separate occasions in temperate (18.1 ± 0.4 °C, 58% ± 8% relative humidity) and on another 2 occasions in hot conditions (32.2 ± 0.7 °C, 55% ± 2% relative humidity). On each occasion, the cyclists exercised in a fed state for 90 min at ~60% VO2max and then completed a 16.1-km time trial. Every 15 min during the first 90 min of exercise, they consumed 0.24 g/kg body mass of a carbohydrate or placebo gel.

Results:

Neutrophil counts increased during exercise in all trials (p < .05) and were significantly lower (40%, p = .006) after the carbohydrate than after the placebo trial in 32 °C. The concentrations of serum interleukin (IL)-6, IL-8, and IL-10 and plasma granulocyte-colony-stimulating factor, myeloperoxidase, and calprotectin also increased during exercise in all trials but did not differ significantly between the carbohydrate and placebo trials. Plasma norepinephrine concentration increased during exercise in all trials and was significantly higher (50%, p = .01) after the carbohydrate vs. the placebo trial in 32 °C.

Conclusion:

Carbohydrate ingestion attenuated neutrophil counts during exercise in hot conditions, whereas it had no effect on any other immune variables in either temperate or hot conditions.

Cover International Journal of Sport Nutrition and Exercise Metabolism

In International Journal of Sport Nutrition and Exercise Metabolism Volume 18 (2008): Issue 3 (Jun 2008)

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The Effect of Dietary Nitrate Supplementation on Physiology and Performance in Trained Cyclists

Joseph A. McQuillan, Deborah K. Dulson, Paul B. Laursen, and Andrew E. Kilding

Purpose:

To determine the effect of dietary nitrate (NO3 –) supplementation on physiology and performance in well-trained cyclists after 6–8 d of NO3 – supplementation.

Methods:

Eight competitive male cyclists (mean ± SD age 26 ± 8 y, body mass 76.7 ± 6.9 kg, VO2peak 63 ± 4 mL · kg–1 · min–1) participated in a double-blind, placebo-controlled, crossover-design study in which participants ingested 70 mL of beetroot juice containing ~4 mmol NO3 – (NIT) or a NO3 –-depleted placebo (PLA), each for 8 d. Replicating pretreatment measures, participants undertook an incremental ramp assessment to determine VO2peak and first (VT1) and second (VT2) ventilatory thresholds on d 6 (NIT6 and PLA6), moderate-intensity cycling economy on d 7 (NIT7 and PLA7), and a 4-km time trial (TT) on d 8 (NIT8 and PLA8).

Results:

Relative to PLA, 6 d of NIT supplementation produced unclear effects for VO2peak (mean ± 95% confidence limit: 1.8% ± 5.5%) and VT1 (3.7% ± 12.3%) and trivial effects for both VT2 (–1.0% ± 3.0%) and exercise economy on d 7 (–1.0% ± 1.6%). However, effects for TT performance time (–0.7% ± 0.9%) and power (2.4% ± 2.5%) on d 8 were likely beneficial.

Conclusions:

Despite mostly unclear outcomes for standard physiological determinants of performance, 8 d of NO3 – supplementation resulted in likely beneficial improvements to 4-km TT performance in well-trained male endurance cyclists.

Cover International Journal of Sports Physiology and Performance

In International Journal of Sports Physiology and Performance Volume 12 (2017): Issue 5 (May 2017)

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Oral Presence of Carbohydrate and Caffeine in Chewing Gum: Independent and Combined Effects on Endurance Cycling Performance

Katherine T. Oberlin-Brown, Rodney Siegel, Andrew E. Kilding, and Paul B. Laursen

The oral presence of carbohydrate (CHO) and caffeine (CAF) may independently enhance exercise performance, but their influence on performance during prolonged exercise is less known.

Aim:

To determine the independent and combined effects of CHO and CAF administered in chewing gum during a cycling time trial (TT) after prolonged exercise.

Method:

Eleven male cyclists (32.2 ± 7.5 y, 74.3 ± 6.8 kg, 60.2 ± 4.0 mL · kg–1 · min–1 V˙O2peak) performed 4 experimental trials consisting of 90-min constant-load cycling at 80% of their second ventilatory threshold (207 ± 30 W), followed immediately by a 20-km TT. Under double-blinded conditions, cyclists received placebo (PLA), CHO, CAF, or a combined CHO+CAF chewing gum at 0-, 5-, 10-, and 15-km points of the TT.

Results:

Overall TT performance was similar across experimental and PLA trials (%mean difference ± 90%CL 0.2% ± 2.0%, 0.4% ± 2.2%, 0.1% ± 1.8% for CHO, CAF, and CHO+CAF). Compared with PLA, mean power output tended to be higher in the first 2 quarters of the TT with CHO (1.6% ± 3.1% and 0.8% ± 2.0%) and was substantially improved in the last 2 quarters during CAF and CHO+CAF trials (4.2% ± 3.0% and 2.0% ± 1.8%). There were no differences in average heart rate (ES <0.2) and only small changes in blood glucose (ES 0.2), which were unrelated to performance. Blood lactate was substantially higher post-TT for CAF and CHO+CAF (ES >0.6).

Conclusion:

After prolonged constant-load cycling, the oral presence of CHO and CAF in chewing gum, independently or in combination, did not improve overall performance but did influence pacing.

Cover International Journal of Sports Physiology and Performance

In International Journal of Sports Physiology and Performance Volume 11 (2016): Issue 2 (Mar 2016)