The skin blood flow response to exercise in boys and men and the role of nitric oxide.

PURPOSE: Children thermoregulate effectively during exercise despite sweating rate being consistently lower when compared with adults. The skin blood flow (SkBF) response of children to exercise is inconsistent, when compared with adults. We examined the SkBF response to exercise in children and adults, along with the potential contribution of nitric oxide to the SkBF response. METHODS: Forearm SkBF during cycling (30 min at 60% [Formula: see text]O2max) was investigated in 12 boys (10 ± 1 years) and 12 men (22 ± 2 years) using laser-Doppler flowmetry and Nω-nitro-L-arginine methyl ester (L-NAME) iontophoresis to inhibit nitric oxide synthase. RESULTS: The exercise-induced SkBF increase was similar in boys and men (mean ± SD, 540 ± 127 vs. 536 ± 103% baseline, respectively, p = 0.43, d = 0.01 [- 0.8 to 0.8]). However, the total hyperaemic response to exercise (area-under-the-curve, AUC) indicated that boys had a greater vasodilatory response (cutaneous vascular resistance, CVC) (p < 0.01, d = 0.6 [- 1.2 to 2.8] than the men (134,215 ± 29,207 vs. 107,257 ± 20,320 CVC·s-1). L-NAME blunted the SkBF response more in boys than in men (group-by-treatment interaction, p < 0.001) and resulted in smaller AUC in boys (56,411 ± 23,033 CVC·s-1; p < 0.001, d = 1.4 [- 0.4 to 3.2] compared with men (80,556 ± 28,443 CVC·s-1; p = 0.08, d = 0.8 [0.0-1.6]). Boys had a shorter delay from the onset of exercise to onset of SkBF response compared with men (205 ± 48 and 309 ± 71 s, respectively; p < 0.01, d = 1.7 [0.9-2.8]). L-NAME increased the delay in boys and men (to 268 ± 90 and 376 ± 116 s, respectively; p = 0.01, d = 1.0 [0.4-2.1]) but this delay was not significantly different between the groups (p = 0.85). CONCLUSIONS: These findings suggest that boys experience greater vasodilation and faster increases in SkBF during exercise compared with men. The contribution of nitric oxide to the SkBF response to exercise appears to be greater in boys than in men.

Correction to: The skin blood flow response to exercise in boys and men and the role of nitric oxide.

One of the co-authors, Raffy Dotan, wishes to remove his name from the original version of this article. The corrected author group should be.

Effects of detraining on left ventricular mass in endurance-trained individuals: a systematic review and meta-analysis.

AIMS: Detraining refers to a loss of training adaptations resulting from reductions in training stimulus due to illness, injury, or active recovery breaks in a training cycle and is associated with a reduction in left ventricular mass (LVM). The purpose of this study was to conduct a systematic review and meta-analysis to determine the influence of detraining on LVM in endurance-trained, healthy individuals. METHODS AND RESULTS: Using electronic databases (e.g. EMBASE and MEDLINE), a literature search was performed looking for prospective detraining studies in humans. Inclusion criteria were adults, endurance-trained individuals with no known chronic disease, detraining intervention >1 week, and pre- and post-detraining LVM reported. A pooled statistic for random effects was used to assess changes in LVM with detraining. Fifteen investigations (19 analyses) with a total of 196 participants (ages 18-55 years, 15% female) met inclusion criteria, with detraining ranging between 1.4 and 15 weeks. The meta-analysis revealed a significant reduction in LVM with detraining (standardized mean difference = -0.586; 95% confidence interval = -0.817, -0.355; P < 0.001). Independently, length of detraining was not correlated with the change in LVM. However, a meta-regression model revealed length of the detraining, when training status was accounted for, was associated with the reduction of LVM (Q = 15.20, df = 3, P = 0.0017). Highly trained/elite athletes had greater reductions in LVM compared with recreational and newly trained individuals (P < 0.01). Limitations included relatively few female participants and inconsistent reporting of intervention details. CONCLUSION: In summary, LVM is reduced following detraining of one week or more. Further research may provide a greater understanding of the effects of sex, age, and type of detraining on changes in LVM in endurance-trained individuals.

In healthy, endurance-trained individuals, detraining results in significant reductions in left ventricular mass. When accounting for training status, the length of the detraining period is positively associated with reductions in left ventricular mass. Limited research on this topic hinders the ability to assess sex differences or the impact of the type of detraining (i.e. only activities of daily living vs. reduced training load) on the response to detraining.

Effects of endurance exercise training on left ventricular structure in healthy adults: a systematic review and meta-analysis.

AIMS: To determine the impact of endurance training (ET) interventions on left ventricular (LV) chamber size, wall thickness, and mass in healthy adults. METHODS AND RESULTS: Electronic databases including CINAHL, MEDLINE, PsycINFO, SPORTDiscus, Cochrane library, and EBM Reviews were searched up to 4 January 2022. Criteria for inclusion were healthy females and/or males (>18 years), ET intervention for ≥2 weeks, and studies reporting pre- and post-training LV structural parameters. A random-effects meta-analysis with heterogeneity, publication bias, and sensitivity analysis was used to determine the effects of ET on LV mass (LVM) and diastolic measures of interventricular septum thickness (IVSd), posterior wall thickness (PWTd), and LV diameter (LVDd). Meta-regression was performed on mediating factors (age, sex, training protocols) to assess their effects on LV structure. Eighty-two studies met inclusion criteria (n = 1908; 19-82 years, 33% female). There was a significant increase in LVM, PWTd, IVSd, and LVDd following ET [standardized mean difference (SMD) = 0.444, 95% confidence interval (CI): 0.361, 0.527; P < 0.001; SMD = 0.234, 95% CI: 0.159, 0.309; P < 0.001; SMD = 0.237, 95% CI: 0.159, 0.316; P < 0.001; SMD = 0.249, 95% CI:0.173, 0.324; P < 0.001, respectively]. Trained status, training type, and age were the only mediating factors for change in LVM, where previously trained, mixed-type training, young (18-35 years), and middle-aged (36-55 years) individuals had the greatest change compared with untrained, interval-type training, and older individuals (>55 years). A significant increase in wall thickness was observed in males, with a similar augmentation of LVDd in males and females. Trained individuals elicited an increase in all LV structures and ET involving mixed-type training and rowing and swimming modalities conferred the greatest increase in PWTd and LVDd. CONCLUSION: Left ventricular structure is significantly increased following ET. Males, young and trained individuals, and ET interventions involving mixed training regimes elicit the greatest changes in LV structure.

Heart structure significantly increases the following endurance training (ET) ≥2 weeks.Changes in heart structure were most prominent in males, who are young (18­35 years), already trained, and following concurrent continuous and interval training.Changes in heart size were not shown in older individuals (>55 years) compared with young and middle-aged individuals.While both males and females similarly increase their cavity size and heart mass, sex differences were revealed for wall thickness where significant increases were seen in males but not females.