Nathaniel J. Thom

Effects of incremental exercise on cerebral oxygenation measured by near-infrared spectroscopy: A systematic review

We conducted a systematic review and meta-regression analysis to quantify effects of exercise on brain hemodynamics measured by near-infrared spectroscopy (NIRS). The results indicate that acute incremental exercise (categorized relative to aerobic capacity (VO(2)peak) as low - <30% VO(2)peak; moderate - ≥30% VO(2)peak to <60% VO(2)peak; hard - ≥60% VO(2)peak to <VO(2)peak; and very hard - ≥VO(2)peak intensities) performed by 291 healthy people in 21 studies is accompanied by moderate-to-large increases (mean effect, dz±95% CI) in the prefrontal cortex of oxygenated hemoglobin (O(2)Hb) or other measures of oxygen level (O(2)Hbdiff) or saturation (SCO(2)) (0.92±0.67, 1.17), deoxygenated hemoglobin (dHb) (0.87±0.56, 1.19), and blood volume estimated by total hemoglobin (tHb) (1.21±0.84, 1.59). After peaking at hard intensities, cerebral oxygen levels dropped during very hard intensities. People who were aerobically trained attained higher levels of cortical oxygen, dHb, and tHb than untrained people during very hard intensities. Among untrained people, a marked drop in oxygen levels and a small increase in dHb at very hard intensities accompanied declines in tHb, implying reduced blood flow. In 6 studies of 222 patients with heart or lung conditions, oxygenation and dHb were lowered or unchanged during exercise compared to baseline. In conclusion, prefrontal oxygenation measured with NIRS in healthy people showed a quadratic response to incremental exercise, rising between moderate and hard intensities, then falling at very hard intensities. Training status influenced the responses. While methodological improvements in measures of brain oxygen are forthcoming, these results extend the evidence relevant to existing models of central limitations to maximal exercise.

Effects of cycling exercise on vigor, fatigue, and electroencephalographic activity among young adults who report persistent fatigue.

We previously reported that 6 weeks of exercise training had positive effects on feelings of vigor and fatigue among college students who reported persistent fatigue. Here we examined whether transient mood changes after single sessions of exercise would mimic those chronic effects and whether they would be related to changes in brain activity measured by electroencephalography (EEG). Feelings of vigor were higher after both low- and moderate-intensity exercise during Weeks 1, 3, and 6 compared to a control condition. Feelings of fatigue were lower after low-intensity exercise during Weeks 3 and 6. Posterior theta activity accounted for about half the changes in vigor. Studies that manipulate mood, EEG activity, or both during exercise are needed to determine whether EEG changes after exercise are causally linked with mood.

Meeting U.S. Healthy People 2010 levels of physical activity: agreement of 2 measures across 2 years.

BACKGROUND Measuring the way people vary across time in meeting recommended levels of physical activity should be a fundamental component of public health surveillance. However, we were unaware of prospective cohort studies that had examined this in a population base using convergent measures. PURPOSE We examined agreement between two validated measures used to estimate periodic change in the rate of meeting U.S. Healthy People 2010 guidelines for participation in moderate or vigorous physical activity. METHODS A cohort (N = 497) from a random, multiethnic sample of adults living in Hawaii was assessed every 6-months for 2 years starting spring 2004. Latent transition analysis classified people as meeting or not meeting the guidelines. Intra-class kappa statistics and multinomial logistic regression analysis were used to evaluate agreement. RESULTS Agreement for classifying stable classes of people who met or did not meet the guideline each time was substantial for vigorous activity (kappa approximately 0.65-0.70) but fair-to-moderate for moderate activity (kappa approximately 0.38-0.48). Agreement was poorer for classifying people who transitioned between meeting and not meeting the vigorous guideline (kappa approximately 0.45) or the moderate guideline (kappa approximately 0.21-0.29). CONCLUSIONS Rates of meeting the guidelines varied across time and were estimated differently by the two measures, especially for moderate activity. This finding illustrates an understudied problem for public health promotion. Accurate classification of change within people is necessary for determining exposure in outcome studies, personal determinants of sufficient activity, and for evaluating whether interventions are successful in sustaining increases in rates of meeting physical activity guidelines.

Effects of exercise on male copulatory behavior after β-adrenoreceptor blockade

UNLABELLED Chronic activity-wheel running enhances male copulation and is associated with brain noradrenergic adaptations that may be modulated by the neuropeptide galanin (GAL). When injected into the medial pre-optic area (MPOA) of the hypothalamus, norepinephrine facilitates, and the beta-adrenoreceptor antagonist propranolol inhibits, male copulation. The present experiment tested whether chronic exercise mitigates copulatory decrements induced by adrenergic blockade in the MPOA. It was hypothesized that 3 weeks of activity-wheel running would (1) reverse deficits in male copulatory performance and (2) increase GAL mRNA in the MPOA after beta-adrenoreceptor blockade with propranolol. MATERIALS AND METHODS Long-Evans male rats were randomly assigned to three experimental groups: sedentary/propranolol, activity-wheel/propranolol, and home-cage control. Animals were chronically administered propranolol in saline vehicle (6 microm/day) via an osmotic mini-pump connected to a cannula implanted into the third ventricle. After 3 weeks of activity-wheel running, rats underwent copulatory testing. After rapid decapitation 24h later, rat brains were analyzed utilizing in situ hybridization histochemistry for GAL mRNA in the MPOA. RESULTS Chronic exercise mitigated reductions in the percentage of males that intromitted and ejaculated after propranolol treatment, but there was no effect of exercise on GAL mRNA. CONCLUSION The findings are consistent with noradrenergic adaptations in the MPOA that facilitate male copulation after wheel running independently of GAL mRNA expression.