Exercise Physiology of Normal Development, Sex Differences, and Aging

Normative values and reference equation for the six-minute step test to evaluate functional exercise capacity: a multicenter study

Objective: To establish normative values and a reference equation for the number of steps climbed during the six-minute step test (6MST) in healthy adults, and to assess the reliability of the test and of the equation. Methods: This was a multicenter cross-sectional study involving 468 healthy volunteers (age range: 18-79 years) recruited from the general community in six research laboratories across different regions of Brazil, which is a country with continental dimensions. The 6MST was performed twice (30-min interval), and clinical, demographic, and functional variables were evaluated. An independent sample of 24 volunteers was evaluated to test the reference equation a posteriori. Results: The number of steps had excellent test-retest reliability (intraclass correlation coefficient = 0.96 [95%CI: 0.95-0.97]), and the mean number of steps was 175 ± 45, the number being 14% greater in males than in females. The best performance on the test was correlated with age (r = -0.60), sex (r = 0.28), weight (r = 0.13), height (r = 0.41), BMI (r = -0.22), waist circumference (r = -0.22), thigh circumference (r = 0.15), FVC (r = 0.54), and physical activity level (r = 0.17; p < 0.05 for all). In the regression analysis, age, sex, height, and weight explained 42% of the variability of the 6MST. Normative values were established for the 6MST according to age and sex. There was no difference between the 6MST values from the independent sample and its predicted values (157 ± 29 steps vs. 161 ± 25 steps; p = 0.47; 97% of predicted values). Conclusions: The normative values and the reference equation for the 6MST in this study seem adequate to accurately predict the physical functional performance in adults in Brazil.

Sex, gender and the pulmonary physiology of exercise

In this review, we detail how the pulmonary system's response to exercise is impacted by both sex and gender in healthy humans across the lifespan. First, the rationale for why sex and gender differences should be considered is explored, and then anatomical differences are highlighted, namely that females typically have smaller lungs and airways than males. Thereafter, we describe how these anatomical differences can impact functional aspects such as respiratory muscle energetics and activation, mechanical ventilatory constraints, diaphragm fatigue, and pulmonary gas exchange in healthy adults and children. Finally, we detail how gender can impact the pulmonary response to exercise.

Biological sex can influence the pulmonary response to exercise in healthy individuals across the lifespanhttps://bit.ly/3ejMDrv

Associations between cardiorespiratory fitness, sex and long term mortality amongst adults undergoing exercise treadmill testing

BACKGROUND

Cardiorespiratory fitness (CRF) varies with sex and is an independent predictor of mortality. We sought to investigate sex differences in the exercise protocol selected, CRF levels, and their relationships with long term all-cause mortality.

METHODS

In a 25-year stress testing registry spanning from 1991 to 2014, consecutive all-comer patients who underwent exercise stress testing at Cleveland Clinic were categorized by sex, stress protocol and imaging modality. All tests were conducted by one or more of stress test technicians, sonographers and nuclear medicine technologists, and interpreted by cardiologists. The primary outcome all-cause mortality was analyzed in using multivariable Cox regression.

RESULTS

In 120,705 patients, the mean age was 53.3 ± 12.5 years, and 41% were female. Females were more commonly referred for non-Bruce exercise protocols (modified Bruce, Cornell 0, 5 and 10, Naughton and modified Naughton) with odds ratio of 2.62; 95% confidence interval (95%CI) (2.54-2.70) after adjusting for age and comorbidities. When also adjusting for the protocol chosen, females achieved lower CRF with beta -1.40, 95% CI (-1.43, -1.37). There were 8426 (6.9%) deaths during a mean follow-up of 8.7 years. Both female sex and CRF were independently associated with lower all-cause mortality with hazards ratio (95%CI) of 0.44 (0.41-0.46) and 0.41 (0.39-0.42) respectively, after adjusting for age, co-morbidities and protocol chosen.

CONCLUSIONS

Women were more likely referred for less demanding exercise protocols, more imaging protocols and achieved lower CRF than men. Despite this, female sex was associated with significantly lower long term mortality for equivalent CRF level in adjusted analyses.

Face Masks and the Cardiorespiratory Response to Physical Activity in Health and Disease

To minimize transmission of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the novel coronavirus responsible for coronavirus disease (COVID-19), the U.S. Centers for Disease Control and Prevention and the World Health Organization recommend wearing face masks in public. Some have expressed concern that these may affect the cardiopulmonary system by increasing the work of breathing, altering pulmonary gas exchange and increasing dyspnea, especially during physical activity. These concerns have been derived largely from studies evaluating devices intentionally designed to severely affect respiratory mechanics and gas exchange. We review the literature on the effects of various face masks and respirators on the respiratory system during physical activity using data from several models: cloth face coverings and surgical masks, N95 respirators, industrial respirators, and applied highly resistive or high-dead space respiratory loads. Overall, the available data suggest that although dyspnea may be increased and alter perceived effort with activity, the effects on work of breathing, blood gases, and other physiological parameters imposed by face masks during physical activity are small, often too small to be detected, even during very heavy exercise. There is no current evidence to support sex-based or age-based differences in the physiological responses to exercise while wearing a face mask. Although the available data suggest that negative effects of using cloth or surgical face masks during physical activity in healthy individuals are negligible and unlikely to impact exercise tolerance significantly, for some individuals with severe cardiopulmonary disease, any added resistance and/or minor changes in blood gases may evoke considerably more dyspnea and, thus, affect exercise capacity.

Age- and Sex-Differences in Cardiac Characteristics Determined by Echocardiography in Masters Athletes

Background

Cardiac function and morphology are known to differ between men and women. Sex differences seen with echocardiography have not been studied systematically in masters athletes.

Purpose

To evaluate sex differences in cardiac structure, function and left ventricular (LV) systolic global longitudinal strain among masters athletes.

Methods

This cross-sectional study comprises of 163 masters athletes (M = 109, 60 ± 12 years; F = 55, 57 ± 12 years, range 36–91 years) who participated at the 23rd World Masters Athletics Championship held in Málaga, Spain. All athletes underwent state-of-the-art echocardiography including cardiac function, morphology, strain and hemodynamic assessment.

Results

Left ventricular mass was higher in male than in female athletes (174 ± 44 vs. 141 ± 36 g, p < 0.01) due to greater end-diastolic intraventricular septal, LV posterior wall and LV basal diameter. However, LV mass index did not differ between the groups. End-diastolic LV volume and right ventricular area, both indexed to body-surface-area, were greater in men than in women (52.8 ± 11.0 vs. 46.1 ± 8.5 ml/m², p < 0.01, 9.5 ± 2.4 vs. 8.1 ± 1.7 cm²/m², p < 0.01). In contrast, women had higher LV systolic global longitudinal strain (-20.2 ± 2.6 vs. -18.8 ± 2.6%, p < 0.01) and LV outflow tract flow velocity (75.1 ± 11.1 vs. 71.2 ± 11.1 cm/s, p = 0.04). Systolic and diastolic blood pressure, LV ejection fraction, and stroke volume index were not different between sexes.

Conclusion

Cardiac sex differences are present even among masters athletes. Lifelong exercise training does not appear to exasperate morphological difference to a point of cardiac risk or dysfunction in both male and female athletes.

Sex differences in paediatric airway anatomy

NEW FINDINGS

What is the central question of this study? Are sex difference in the central airways present in healthy paediatric patients? What is the main finding and its importance? In patients ≤12 years we found no sex differences in central airway luminal area. After 14 years, the males had significantly larger central airway luminal areas than the females. The sex differences were minimized, but preserved when correcting for height. Luminal area is the main determinant of airway resistance and our finding could help explain sex differences in pulmonary system limitations to exercise in paediatric patients.

ABSTRACT

Cross-sectional airway area is the main determinant of resistance to airflow in the respiratory system. In paediatric patients (<18 years), previous evidence for sex differences in cross-sectional airway area was limited to patients with history of pulmonary disease or cadaveric studies with small numbers of subjects. These studies either only report tracheal data and do not include a range of ages or correct for height. Therefore, we sought to assess sex differences in airway luminal area utilizing paediatric patients of varying ages and no history of respiratory disease. Using three-dimensional reconstructions from high-resolution computed tomography scans, we retrospectively assessed the cross-sectional airway area in healthy paediatric females (n = 97) and males (n = 128) over a range of ages (1-17 years). The areas of the trachea, left main bronchus, left upper lobe, left lower lobe, right main bronchus, intermediate bronchus and right upper lobe were measured at three discrete points by a blinded investigator. No differences between the sexes were noted in the cross-sectional areas of the youngest (ages 1-12 years) patients (P > 0.05). However, in patients ≥14 years the cross-sectional areas were larger in the males compared to females in most airway sites. For instance, the cross-sectional size of the trachea was 25% (218 ± 44 vs. 163 ± 24 mm² , P < 0.01) larger in males vs. females among ages 13-17 years. When accounting for height, these sex differences in airway areas were attenuated, but persisted. Our results indicate that sex differences in paediatric airway cross-sectional area manifest after age ≥14 years and are independent of height.

Does competitive swimming affect lung growth?

Whether the large lungs of swimmers result from intensive training or genetic endowment has been widely debated. Given that peak lung growth velocities occur during puberty, this study examined if competitive swimming during puberty affected lung growth. Eleven- to fourteen-year-old healthy female competitive swimmers and controls were assessed before (PRE) and after (POST) one swimming season (7.4 ± 0.5 months). Pulmonary function testing included lung volumes, spirometry, diffusion capacity (DL,CO ), and maximal inspiratory (PIMAX ) and expiratory (PEMAX ) pressures. Ventilatory constraints, including end-expiratory lung volume, expiratory flow limitation, and utilization of ventilatory capacity, were assessed during an incremental cycling test. Swimmers (n = 11) and controls (n = 10) were of similar age, size, and sexual maturity (P > 0.05). However, swimmers compared to controls had a greater total lung capacity (PRE 4.73 ± 0.73 vs. 3.93 ± 0.46, POST 5.08 ± 0.68 vs. 4.19 ± 0.64 L; P < 0.01), peak expiratory flow (PRE 6.48 ± 0.92 vs. 5.70 ± 0.86, POST 6.97 ± 0.84 vs. 6.00 ± 0.77 L·s-1 ; P = 0.03), and PEMAX (P < 0.001). Although DL,CO was greater in swimmers (P = 0.01), differences were attenuated when expressed relative to alveolar volume (PRE 5.14 ± 0.60 vs. 5.44 ± 0.44, POST 4.91 ± 0.56 vs. 5.16 ± 0.38 mL min-1  mmHg-1  L-1 ; P = 0.20). The groups achieved a similar maximal oxygen uptake (P = 0.32), and ventilatory constraints experienced were not different (P > 0.05). Changes over time were not different between groups (P > 0.05). At the initial measurement, pubertal female swimmers had greater lung size, expiratory flows, and indices of respiratory muscle strength, but similar ventilatory constraints while cycling. One competitive swimming season did not further accentuate this enhanced lung size and function or alter ventilatory mechanics, suggesting that competitive swimming during puberty did not affect lung growth.

Mediator Effect of Balance Problems on Association Between Grip Strength and Falls in Older Adults: Results From the KORA-Age Study

Objective: To examine the association between grip strength and history of falls among older individuals, and to assess the possible mediating effect of balance problems on this relationship. Method: Data originate from KORA (Cooperative Health Research in the Region of Augsburg)-Age Study of 808 individuals (65 years and above). Follow-up assessment occurred 3 years later. Results: The risk of falls within the last 12 months was reduced on average by 3% (odds ratio [OR] 95% confidence interval [95% CI] = 0.97 [0.94, 0.99]; p value = .026) per 1-kg increase in maximum grip strength after adjusting for age and gender. There was a trend toward an indirect effect of grip strength through the mediator variable balance problems (p value = .043). Discussion: Increased muscular strength is associated with a reduced risk of falls in older age after adjustment for age and gender. The association is partially mediated by balance problems. Thus, in older adults, muscle-strengthening exercises may decrease the risk of falling.