Capillary Cortisol Sampling during High-Intensity Exercise

Brief exercise enhances intrusive memories of traumatic stimuli

Brief physical exercise enhances memories for neutral events, and recently has been shown to modulate fear learning in animals. To date there is no evidence pertaining to the impact of exercise on emotional memories in humans. Accordingly, this study investigated the role of brief exercise in the development of emotional intrusive memories. Forty-nine university students (18-29year olds) viewed a car accident film depicting accident and injury, and were then randomly assigned to engage in either 10min of intense exercise or easy walking. Two days following the experiment participants were assessed for both intrusive memories of the film and intentional recall of film details. Results indicated that participants in the exercise relative to the walking condition reported more intrusive memories, but not voluntarily recalled memories, of the car accident film two days later. These findings are consistent with recent evidence of exercise-induced emotional learning in animals, and point to the potential for physical activity to contribute to the development of intrusions in the context of encoding emotionally-laden information.

The utility of salivary testosterone and cortisol concentration measures for assessing the stress responses of junior athletes during a sporting competition

BACKGROUND

This study examined the utility of salivary testosterone (T) and cortisol (C) concentration measures for assessing the acute stress responses of junior athletes during a sporting competition.

METHODS

Paired capillary blood and saliva samples were taken from 71 junior athletes (45 males, 26 females) before and after a simulated Olympic weightlifting competition. The concentration measures of salivary T and C were referenced against blood total T (TT) and C (TC) concentrations. All hormones were tested by immunoassay.

RESULTS

The competition promoted an increase in the blood TT concentrations of the male (10.1%±18.7%) and female (12.9%±19.9%) athletes (P<.05), with TC also rising in females (37.5%±69%) and tending to increase in males (23.2%±56.1%). No significant changes in salivary T or C were identified. Locally-weighted regression revealed that salivary T was strongly related to blood TT in males (r² =.84), but not females (r² =-.15), whereas salivary C was moderately related to blood TC in both sexes (r² =.43, r² =.48), respectively.

CONCLUSIONS

A short, high-intensity competition promoted a predictable stress-induced rise in blood TT and TC concentrations. We observed no hormonal stress responses in saliva under the current format, which could be explained by individual variability and blood-saliva differences in hormone kinetics. Still, the salivary T and C measures did show a moderate to strong ability to track individual blood TT (males only) and TC (both sexes) concentrations in a young athletic cohort across a broad physiological range. Recommendations for researchers and practitioners are presented.

Role of BDNF val66met polymorphism in modulating exercised-induced emotional memories

Brief physical exercise enhances memories for neutral events, and modulates fear learning in animals. Exercise-induced arousal induces the release of brain-derived neurotrophic factor (BDNF), which may moderate memory-enhancing effects. This study investigated the effect of exercise, and the extent to which the BDNF val66met polymorphism (which limits BDNF activity-dependent secretion) influenced emotional memories. Sixty-two healthy participants were randomly assigned to either 10min of intense exercise (n=31) or slow walking (control condition; n=31), and then immediately viewed positive and negative images. Saliva samples were collected to index salivary cortisol, and to determine BDNF val66met genotype. Participants completed memory questionnaires two days later. Participants in the exercise had a significant increase in cortisol, and recalled more emotional images relative to the walking condition. Regression analyses indicated that the interaction between the BDNF val/val allele and cortisol response predicted stronger emotional memory in the exercise condition. These findings are consistent with evidence of acute exercise-induced emotional learning in animals, and suggests that a genetic predisposition involving BDNF may be important in determining the impact of acute exercise on emotional memory formation.

A single bout of resistance exercise can enhance episodic memory performance

Acute aerobic exercise can be beneficial to episodic memory. This benefit may occur because exercise produces a similar physiological response as physical stressors. When administered during consolidation, acute stress, both physical and psychological, consistently enhances episodic memory, particularly memory for emotional materials. Here we investigated whether a single bout of resistance exercise performed during consolidation can produce episodic memory benefits 48 h later. We used a one-leg knee extension/flexion task for the resistance exercise. To assess the physiological response to the exercise, we measured salivary alpha amylase (a biomarker of central norepinephrine), heart rate, and blood pressure. To test emotional episodic memory, we used a remember-know recognition memory paradigm with equal numbers of positive, negative, and neutral IAPS images as stimuli. The group that performed the exercise, the active group, had higher overall recognition accuracy than the group that did not exercise, the passive group. We found a robust effect of valence across groups, with better performance on emotional items as compared to neutral items and no difference between positive and negative items. This effect changed based on the physiological response to the exercise. Within the active group, participants with a high physiological response to the exercise were impaired for neutral items as compared to participants with a low physiological response to the exercise. Our results demonstrate that a single bout of resistance exercise performed during consolidation can enhance episodic memory and that the effect of valence on memory depends on the physiological response to the exercise.

Direct measurement of cell-free DNA from serially collected capillary plasma during incremental exercise

To investigate the kinetics of cell-free DNA (cfDNA) due to exercise, we established a direct real-time PCR for the quantification of cfDNA from unpurified capillary plasma by amplification of a 90- and a 222-bp multilocus L1PA2 sequence. Twenty-six male athletes performed an incremental treadmill test. For cfDNA measurement, capillary samples were collected serially from the fingertip preexercise, during, and several times postexercise. Venous blood was drawn before and immediately after exercise to compare capillary and venous cfDNA values. To elucidate the strongest association of cfDNA accumulations with either cardiorespiratory or metabolic function during exercise, capillary cfDNA values were correlated with standard measures like heart rate, oxygen consumption, or lactate concentrations. The venous cfDNA concentrations were significantly higher compared with the capillary plasma, but in both fractions cfDNA increased 9.8-fold and the values correlated significantly ( r = 0.796). During incremental treadmill running, the capillary cfDNA concentrations increased nearly parallel to the lactate values. The values correlated best with heart rate and energy expenditure, followed by oxygen consumption, Borg values, and lactate levels (0.710 ≤ r ≥ 0.808). With this article, we present a sensitive procedure for the direct quantification of cfDNA in unpurified capillary plasma instead of purified venous plasma. Further studies should investigate the differences between capillary and venous cfDNA that might mirror different physiological mechanisms. Enhanced cardiorespiratory function during exercise might lead to the accumulation of cfDNA via the release of stress hormones that already increase at intensities below the anaerobic threshold. Furthermore, cfDNA might be released by neutrophil extracellular traps.