Mechanical efficiency improvement in relation to metabolic changes in sedentary obese adults

Determinants of mechanical efficiency trajectories from childhood to adolescence: Findings from the QUALITY cohort

PURPOSE

To estimate the shape and number of mechanical efficiency (ME) trajectories from childhood to adolescence; and verify whether ME trajectory membership can be predicted by sex, biological maturation, body weight, body composition and physical activity (PA) in childhood.

METHODS

Data from QUALITY, an ongoing cohort study on the natural history of obesity, were used. Participants attended a baseline visit (8-10 years, n = 630) and follow-up visits two years (n = 564), and seven years (n = 377) later. ME was assessed by an incremental cycling test at 50w (ME_50w, %) and at VO_2peak (ME_VO2peak, %). Group-based trajectory analysis for ME and a logistic regression were performed.

RESULTS

Mean age of the 454 participants (boys = 54%) was 9.7 ± 0.9 years at baseline. Two distinct ME_50w trajectories were identified and all tended to decrease. No distinct trajectories emerged for ME_VO2peak; average ME_VO2peak increased over time. Thus, the difference between ME_VO2peak (∆) at baseline and follow-up was calculated for correlation analysis. Trajectory groups were labeled "Low-Decreaser" and "High-Decreaser" (Reference) for ME_50w, describing the starting point and slope. High-Decreasers were mostly prepubertal girls, had lower body weight and fat free mass index, lower PA and lower VO_2peak at baseline (χ²or t-test, p < 0.05). Girls were less likely to be Low-Decreasers (OR = 0.56, 95%CI = 0.42-0.74), while having overweight/obesity predicted a greater likelihood of classification in the Low-Decreaser trajectory (OR = 2.38, 95%CI = 1.16-4.88). Those with higher PA were more likely to be Low-Decreasers (OR = 1.02, 95%CI = 1.01-1.04). Finally, concerning ME_VO2peak, sex, biological maturation, body weight, zBMI, fat free mass index, PA and VO_2peak were positively correlated with ∆ ME_VO2peak.

CONCLUSIONS

We found evidence that excess weight at baseline predicts low levels of ME in childhood and adolescence. Additionally, higher PA at baseline is not related to higher ME_50w levels. More research is needed to identify different approaches to explore this measure in transition to adulthood.

Impaired pulmonary and muscle function during moderate exercise in female patients recovered from SARS-CoV-2

This study aimed to assess pulmonary and muscle dysfunction by analyzing the slow component of oxygen uptake (VO2SC), and mechanical and ventilatory efficiency in adult women recovered from the severe acute respiratory syndrome coronavirus type II (SARS-CoV-2) during a constant load test. 32 women (N = 17 patients with SARS-CoV-2; N = 15 control group) performed two cardiopulmonary exercise tests (CPX) on a cycle ergometer. In the first test, the participants performed incremental CPX until extenuation. In the second test the participants performed a 10-min CPX at a constant load intensity (watts) corresponding to the first ventilatory threshold. There was a 48-72 h rest period between the two tests. There was a significant increase in the VO2SC in the patients recovered from SARS-CoV-2 (160.4 ± 60 mL min-1) in comparison with the healthy participants (59.6 ± 65 mL min-1) (P < 0.001). Mechanical efficiency significantly decreased in patients recovered from SARS-CoV-2 compared to the control group (P = 0.04). Ventilatory inefficiency significantly increased in the patients recovered from SARS-CoV-2 compared with the control group (P < 0.001). Adult women recovered from SARS-CoV-2 infection have important pulmonary and muscular dysfunction and fatigue which contributes to increasing the VO2SC and reducing mechanical and ventilatory efficiency during mild-moderate exercise at a constant load.

A Systematic Review and Meta-Analysis of Tai Chi Training in Cardiorespiratory Fitness of Elderly People

Objectives

The purpose of this study was to investigate the influence of Tai Chi on cardiorespiratory fitness (CRF) in elderly people using meta-analysis.

Methods

This study used seven electronic databases and data retrieved from randomized controlled trials (RCTs) investigating the role of Tai Chi on CRF in the elderly. All these 24 RCTs were screened and selected from 7 literature databases. The Stata 11.2 software (StataCorp, USA) was used for the meta-analysis, subgroup analysis, and bias test, while the Cochrane Collaboration's tool was used for the assessment of the risk of bias (RoB). 4 researchers independently participated in sample selection, data extraction, and RoB assessment.

Results

Following the inclusion criteria, 24 eligible studies were included in our analysis. The meta-analysis indicated that Tai Chi practice significantly increased the maximum rate of oxygen consumption (VO_{2 max}) (weighted mean difference (WMD)  = 3.76, 95% CI: 1.25 to 6.26, P < 0.1), leading to an overall reduction in the heart rate (HR) (WMD  = −1.84, 95% CI: −2.04 to −1.63, P  ≤ 0.001) and an increase in the O_{2 pulse} (WMD = 0.94, 95% CI: 0.60 to 1.28, P ≤ 0.001) in individuals who practiced Tai Chi regularly compared with those who did not. The subgroup analysis suggested that overall in those who practiced Tai Chi, males (WMD = 1.48, 95% CI: 0.85 to 2.12, P ≤ 0.001) had higher O_{2 pulse} than females (WMD = 0.73, 95% CI: 0.33 to 1.12, P ≤ 0.001). The subgroup analysis also showed an increase in the vital capacity (VC) (WMD = 316.05, 95% CI: 239.74 to 392.35, P ≤ 0.001) in individuals practicing Tai Chi. When the samples were further stratified by Tai Chi practicing time, the subgroup analysis suggested that individuals practicing Tai Chi over a period of 24 weeks showed no significant difference in VC (WMD = 82.95, 95% CI: -98.34 to 264.23, P=0.370), while those practicing Tai Chi over a period of 48 weeks showed a significant increase (WMD = 416.62, 95% CI: 280.68 to 552.56, P ≤ 0.001). Furthermore, the subgroup analysis demonstrated that the increase in VC is significantly correlated with the Tai Chi practicing time (WMD = 344.97, 95% CI: 227.88 to 442.06, P ≤ 0.001).

Conclusion

Regular Tai Chi practice could improve the CRF in the elderly, as indicated by significant improvement in indicators including VO_2max, O_2pulse, VC, and HR. However, gender and practice time might influence the overall beneficial outcomes.

The Effects of Sodium Phosphate Supplementation on the Cardiorespiratory System and Gross Efficiency during Exercise under Hypoxia in Male Cyclists: A Randomized, Placebo-Controlled, Cross-Over Study

The main aim of this study was to evaluate the effects of six days of tri-sodium phosphate (SP) supplementation on the cardiorespiratory system and gross efficiency (GE) during exercise under hypoxia in cyclists. Twenty trained male cyclists received SP (50 mg·kg⁻¹ of fat-free mass/day) or placebo for six days in a randomized, cross-over study, with a three-week washout period between supplementation phases. Before and after each supplementation phase, the subjects performed an incremental exercise test to exhaustion under normobaric hypoxia (FiO₂ = 16%, ~2500 m). It was observed that short-term SP supplementation led to a decrease in heart rate, an increase in stroke volume, and an improvement in oxygen pulse (VO₂/HR) during low and moderate-intensity exercise under hypoxia. These changes were accompanied by an increase in the serum inorganic phosphate level by 8.7% (p < 0.05). No significant changes were observed in serum calcium levels. GE at a given workload did not change significantly after SP supplementation. These results indicated that SP promotes improvements in the efficiency of the cardiorespiratory system during exercise in a hypoxic environment. Thus, SP supplementation may be beneficial for endurance exercise in hypoxia.

Eijnde B, Dendale P, Hansen D, Verboven K. Aberrant Mechanical Efficiency during Exercise Relates to Metabolic Health and Exercise Intolerance in Adolescents with Obesity

BACKGROUND

Mechanical efficiency (ME) might be an important parameter evaluating cardiometabolic health and the effectiveness of physical activity interventions in individuals with obesity. However, whether these cardiometabolic risk factors may relate to ME in adolescents with obesity is not known yet. Therefore, this study aims to compare the mechanical efficiency during maximal exercise testing between adolescents with obesity and lean adolescents, and to examine associations with exercise tolerance and metabolic health.

METHODS

Twenty-nine adolescents with obesity (BMI SDS: 2.11 ± 0.32, age: 13.4 ± 1.1 years, male/female: 15/14) and 29 lean (BMI SDS: -0.16 ± 0.84, age: 14.0 ± 1.5 years, male/female: 16/13) adolescents performed a maximal cardiopulmonary exercise test from which the net mechanical efficiency (ME_net) and substrate oxidation (carbohydrates and lipids) were calculated. Indicators for peak performance were collected. Biochemistry (lipid profile, glycaemic control, inflammation, leptin) was studied in fasted blood samples. Regression analyses were applied to examine relations between ME_net and exercise tolerance or blood variables in the total group.

RESULTS

Peak work rate (WR_peak), oxygen uptake (V˙O2peak)/WR_peak, ME, and ME_net were significantly lower (p < 0.05) in adolescents with obesity compared to their lean counterparts (p < 0.05). Furthermore, a reduced ME_net was independently related to a lower WR_peak (SC β = 2.447; p < 0.001) and elevated carbohydrate oxidation during exercise (SC β = -0.497; p < 0.001), as well as to elevated blood low-density lipoprotein cholesterol (SC β = -0.275; p = 0.034) and fasting glucose (SC β = -0.256; p = 0.049) concentration.

CONCLUSION

In adolescents with obesity, the mechanical efficiency is lowered during exercise and this relates to exercise intolerance and a worse metabolic health.

Severe loss of mechanical efficiency in COVID-19 patients

BACKGROUND

There is limited information about the impact of coronavirus disease (COVID-19) on the muscular dysfunction, despite the generalized weakness and fatigue that patients report after overcoming the acute phase of the infection. This study aimed to detect impaired muscle efficiency by evaluating delta efficiency (DE) in patients with COVID-19 compared with subjects with chronic obstructive pulmonary disease (COPD), ischaemic heart disease (IHD), and control group (CG).

METHODS

A total of 60 participants were assigned to four experimental groups: COVID-19, COPD, IHD, and CG (n = 15 each group). Incremental exercise tests in a cycle ergometer were performed to obtain peak oxygen uptake (VO₂ peak). DE was obtained from the end of the first workload to the power output where the respiratory exchange ratio was 1.

RESULTS

A lower DE was detected in patients with COVID-19 and COPD compared with those in CG (P ≤ 0.033). However, no significant differences were observed among the experimental groups with diseases (P > 0.05). Lower VO₂ peak, peak ventilation, peak power output, and total exercise time were observed in the groups with diseases than in the CG (P < 0.05). A higher VO₂ , ventilation, and power output were detected in the CG compared with those in the groups with diseases at the first and second ventilatory threshold (P < 0.05). A higher power output was detected in the IHD group compared with those in the COVID-19 and COPD groups (P < 0.05) at the first and second ventilatory thresholds and when the respiratory exchange ratio was 1. A significant correlation (P < 0.001) was found between the VO₂ peak and DE and between the peak power output and DE (P < 0.001).

CONCLUSIONS

Patients with COVID-19 showed marked mechanical inefficiency similar to that observed in COPD and IHD patients. Patients with COVID-19 and COPD showed a significant decrease in power output compared to IHD during pedalling despite having similar response in VO₂ at each intensity. Resistance training should be considered during the early phase of rehabilitation.

Comparison of performance and health indicators between perimenopausal and postmenopausal obese women: the effect of high-intensity interval training (HIIT)

OBJECTIVE

This study examined the effects of 6 weeks of high-intensity interval training (HIIT) on performance and health indicators in obese perimenopausal (PERIM) women and similarly aged and older postmenopausal women (POSTM1 and POSTM2, respectively).

METHODS

Sixteen PERIM women (average age 49.6 y), 21 POSTM1 women (average age 50.6 y), and 19 POSTM2 women (average age 69.6 y) completed a 6-week HIIT intervention. Anthropometric parameters, mechanical efficiency (ME in %), lipid oxidation (LO in %), and low and high spectral frequencies (LF[ms2] and HF[ms2]) were computed pre- and postintervention.

RESULTS

PERIM women showed a significantly higher VO2max preintervention compared to POSTM1 and 2 (P < 0.01). Moreover, HF, LF, and the LF/HF ratio differed significantly in PERIM women preintervention compared to POSTM1 and 2 (P < 0.01, respectively). After 6 weeks, a significant decrease in anthropometric variables was observed for all groups (P < 0.01). The VO2max in mL/kg/min increased for all groups (P < 0.01). Multiple linear regression analysis demonstrated that age contributed significantly to differences in VO2max values between groups preintervention (r = 0.72). This model accounted for 34% (r2 = 0.34) of the variation. On the other hand, menopause status was an independent predictor of LO, accounting for 38% of the variation, as well as of HF (33%), LF (29%), and the LF/HF ratio (24%). After HIIT, no age or menopause effect was detected for these independent variables.

CONCLUSIONS

Maximal oxygen consumption, HF, LF, and the LF/HF ratio differ among women according to the menopausal status and age. A 6-week HIIT intervention improved many health and performance parameters and reduced the effects of menopause and age.

Mechanical Efficiency at Different Exercise Intensities Among Adolescent Boys With Different Body Fat Levels

This study investigated the mechanical efficiency (ME) and associated factors in obese, overweight, and normal-weight adolescent boys during incremental cycle exercise test to exhaustion. Forty-five sedentary adolescent boys (13–14 years old) were separated in three groups according to the percentage of fat mass as follows: 15 normal-weight (NW) (body fat: 16.0 ± 1.9%), 15 overweight (OW) (body fat: 24.0 ± 1.6%), and 15 obese (OB) (body fat: 31.0 ± 3.0%). All groups completed an incremental cycle exercise to exhaustion in which energy consumption (E, W), ME (%), lipid oxidation rate (LO, %), plasma epinephrine and norepinephrine concentrations were determined consecutively at rest and at three intensity levels corresponding to 50 and 75% of each participant’s maximal heart rate (50%HRmax and 75%HRmax) and peak oxygen consumption (V˙O_2peak). During the incremental cycle exercise test, plasma epinephrine, and norepinephrine responses as well as ME determined at 50%HRmax, 75%HRmax, and at VO_2peak stages were significantly lower in OB compared to NW and OW individuals (ps < 0.01). Multiple linear regressions showed that body weight (ß = -0.64, p < 0.001), energy consumption (ß = -0.24, p < 0.05) and lipid oxidation (ß = 0.69, p < 0.01) were significant predictors of ME at 50%HRmax. However, at 75%HRmax and V˙O_2peak, significant predictors of ME were epinephrine (ß = 0.34, ß = 0.49, respectively, ps = 0.01), norepinephrine (ß = 0.26, ß = 0.60, respectively, ps < 0.05) and power output (ß = 0.62, ß = 0.71, respectively, ps < 0.01). These findings suggest that excess in body weight exerts a negative effect on ME at a low intensity by increasing energy consumption for obese and overweight adolescent boys, while at higher intensities (75%HRmax and VO_2peak) the lower ME could be better explained by the lower power output and catecholamine responses that were attenuated among obese and overweight adolescent boys.

Ratings of Perceived Exertion Misclassify Intensities for Sedentary Older Adults During Graded Cycling Test: Effect of Supramaximal High-Intensity Interval Training

The present study aims (1) to evaluate ratings of perceived exertion (RPE) and corresponding intensities during a maximal graded cycling test and (2) to determine the effects of 6 weeks of supramaximal cycling exercise (SCE) intervention on RPE and associated physiological factors in young and older sedentary groups. Two healthy groups of 17 young adults [average (SD) age: 26.2 (2.4) year] and 13 older adults [average (SD) age: 54.5 (2.3) year] completed a 6-week SCE intervention on an ergocycle. Physiological values and RPE were collected across stages corresponding to ventilator thresholds 1 (VT1) and 2 (VT2) of the graded cycling test and 10 min following the end of test and during the six bouts of SCE. The relative intensity for both VT1 and VT2 were also objectively calculated based on the percent of maximal heart rate %HRmax and peak oxygen consumption %V˙O₂peak.

Before SCE intervention, RPE values were significantly higher for the older group compared to younger at VT1 [p < 0.01] and VT2 [p < 0.01], although both groups were working at similar relative intensities (%V˙O₂). After 6 weeks of SCE, the older group’s perceived effort values were normalized to the actual estimated ones and were similar to those observed in younger individuals. The intervention elicited physiological changes at rest and submaximal intensities, while no improvements were noted for both groups in aerobic fitness (i.e., V˙O₂peak). For both groups, RPE decreases with SCE at 10 min following graded test correlated significantly to V˙O₂ (r = 0.61, p < 0.01). Our study revealed that the initial over-estimation of the exertion levels found for the older sedentary group at the tested submaximal intensities was no longer present after 6 weeks of SCE training, therefore matching RPE values of the young group and those estimated by %HRmax and %V˙O₂peak methods. Therefore, combining the RPE method with other commonly used methods of estimating exercise intensity is highly recommended for sedentary older adults to suitably monitor the exercise intensity.

Muscle Free Fatty-Acid Uptake Associates to Mechanical Efficiency During Exercise in Humans

Intrinsic factors related to muscle metabolism may explain the differences in mechanical efficiency (ME) during exercise. Therefore, this study aimed to investigate the relationship between muscle metabolism and ME. Totally 17 healthy recreationally active male participants were recruited and divided into efficient (EF; n = 8) and inefficient (IE; n = 9) groups, which were matched for age (mean ± SD 24 ± 2 vs. 23 ± 2 years), BMI (23 ± 1 vs. 23 ± 2 kg m-2), physical activity levels (3.4 ± 1.0 vs. 4.1 ± 1.0 sessions/week), and V ˙ O2peak (53 ± 3 vs. 52 ± 3 mL kg-1 min-1), respectively, but differed for ME at 45% of V ˙ O2peak intensity during submaximal bicycle ergometer test (EF 20.5 ± 3.5 vs. IE 15.4 ± 0.8%, P < 0.001). Using positron emission tomography, muscle blood flow (BF) and uptakes of oxygen (m V ˙ O2), fatty acids (FAU) and glucose (GU) were measured during dynamic submaximal knee-extension exercise. Workload-normalized BF (EF 35 ± 14 vs. IE 34 ± 11 mL 100 g-1 min-1, P = 0.896), m V ˙ O2 (EF 4.1 ± 1.2 vs. IE 3.9 ± 1.2 mL 100 g-1 min-1, P = 0.808), and GU (EF 3.1 ± 1.8 vs. IE 2.6 ± 2.3 μmol 100 g-1 min-1, P = 0.641) as well as the delivery of oxygen, glucose, and FAU, as well as respiratory quotient were not different between the groups. However, FAU was significantly higher in EF than IE (3.1 ± 1.7 vs. 1.7 ± 0.6 μmol 100 g-1 min-1, P = 0.047) and it also correlated with ME (r = 0.56, P = 0.024) in the entire study group. EF group also demonstrated higher use of plasma FAU than IE, but no differences in use of plasma glucose and intramuscular energy sources were observed between the groups. These findings suggest that the effective use of plasma FAU is an important determinant of ME during exercise.

Mechanical efficiency of high versus moderate intensity aerobic exercise in coronary heart disease patients: A randomized clinical trial

BACKGROUND

Mechanical efficiency (ME) refers to the ability of an individual to transfer energy consumed by external work. A decreased ME, could represent an increased energy cost during exercise and may, therefore, be limited in terms of physical activity. This study aimed to compare the influence of two different exercise protocols: moderate continuous training (MCT) versus high intensity interval training (HIIT), as part of a cardiac rehabilitation program on ME values among coronary patients.

METHODS

One hundred and ten coronary patients were assigned to either HIIT or MCT groups for 8 weeks. Incremental exercise tests in a cycle ergometer were performed to obtain VO2peak. Net energy expenditure (EE) and ME were obtained at intensities corresponding to the first (VT1) and second (VT2) ventilatory thresholds, and at VO2peak.

RESULTS

Both exercise programs significantly increase VO2peak with a higher increase in the HIIT group (2.96 ± 2.33 mL/kg/min vs. 3.88 ± 2.40 mL/kg/min, for patients of the MCT and HIIT groups, respectively, p < 0.001). The ME at VO2peak and VT2 only significantly increased in the HIIT group. At VT1, ME significantly increased in both groups, with a greater increase in the HIIT group (2.20 ± ± 6.25% vs. 5.52 ± 5.53%, for patients of the MCT and HIIT groups, respectively, p < 0.001).

CONCLUSIONS

The application of HIIT to patients with chronic ischemic heart disease of low risk re- sulted in a greater improvement in VO2peak and in ME at VT1, than when MCT was applied. Moreover, only the application of HIIT brought about a significant increase in ME at VT2 and at VO2peak.

High-intensity interval training improves performance in young and older individuals by increasing mechanical efficiency

This study evaluated the effects of 6 weeks of high‐intensity interval training (HIIT) on mechanical efficiency (ME) in young and older groups. Seventeen healthy young adults [26.2(2.4) year], and thirteen healthy older adults [54.5(2.3) year] completed a 6‐week HIIT intervention (three sessions per week) on an electromagnetically braked cycle ergometer. Each HIIT session contained six repetitions of supramaximal exercise intervals (6 seconds each) with 2 min of passive recovery between each repetition. ME (%) were computed in net terms across stages corresponding to ventilator thresholds 1 (VT1) and 2 (VT2) and at 100% of maximal oxygen consumption (VO₂max) of an incremental maximal cycling test. After 6 weeks, the ME values did not differ between the two groups and were significantly higher than the ones at baseline (P < 0.01). In this study, the multiple linear regression analysis demonstrated the increases in maximal power (Pmax) contributed significantly to ME increases over 6 weeks at VT1, VT2 and at 100% of VO_2max. This model accounted respectively for 28, 38, and 42%, of the increases. In older adults, ME determined during incremental maximal cycling test increases at VT1, VT2 and at 100% over 6‐week HIIT intervention, and the increment appeared to be related to increases in Pmax. HIIT can be recommended as a strategy aimed at improving muscle efficiency among older adults.