Increased resting energy expenditure after 40 minutes of aerobic but not resistance exercise

Effects of 10 weeks of walking-based exercise training on resting substrate oxidation in postmenopausal women with obesity

BACKGROUND AND AIMS

Accumulating evidence supports the effectiveness of moderate-intensity aerobic training on metabolic health, with limited studies investigating change in resting substrate oxidation. The aim of this study was to explore whether 10 weeks of walking-based aerobic training would alter substrate oxidation in postmenopausal women with obesity.

METHODS AND RESULTS

Twenty-four postmenopausal women with obesity who were assigned into the control (n = 12) or exercise groups (n = 12) undertook a 10-week aerobic training program (3 d·week-1) that involved walking exercises at 50-70% of heart rate reserve on a treadmill, with exercise volume increased from 25 to 40 min·day-1. Resting metabolic rate (RMR) and body composition were measured pre- and post-training. Whole-body substrate oxidation was calculated using respiratory data collected during RMR measurement via indirect calorimetry. No significant change was noted (p > 0.05) in resting fat oxidation and carbohydrate oxidation in the exercise group. Resting respiratory exchange ratio and RMR did not alter in response to the training program (p > 0.05).

CONCLUSION

Our results show that a 10-week of moderate-intensity aerobic training does not modify substrate oxidation in postmenopausal women with obesity.

The Effect of Exercise Training on Blood Lipids: A Systematic Review and Meta-analysis

BACKGROUND

Dyslipidemia is a primary risk factor for cardiovascular disease (CVD). Exercise training (EXTr) improves some lipid markers but not others; the literature is dated and analyses may be underpowered.

OBJECTIVES

To clarify which lipid markers are altered with ExTr and establish if information size had yet reached futility.

METHODS

We conducted a systematic review/meta-analysis, with meta-regression, to establish expected effect size in lipid profile with aerobic (AT), resistance (RT) and combined (CT = AT + RT) ExTr. We conducted trial sequence analysis (TSA) to control for type I and II error and establish if information size had reached futility.

RESULTS

We included 148 relevant randomized controlled trials (RCTs) of ExTr, with 227 intervention groups, total 8673 participants; exercise 5273, sedentary control 3400. Total cholesterol (TC) MD - 5.90 mg/dL (95% confidence interval (CI) - 8.14, - 3.65), high-density lipoprotein cholesterol (HDL) 2.11 (95% CI 1.43, 2.79), low-density lipoprotein cholesterol (LDL) - 7.22 (95% CI - 9.08, - 5.35), triglycerides - 8.01 (95% CI - 10.45, - 5.58) and very low-density lipoprotein cholesterol (VLDL) - 3.85 (95% CI - 5.49, - 2.22) all showed significant but modest 3.5-11.7%, improvements following ExTr. TSA indicated all analyses exceeded minimum information size to reach futility. CT was optimal for dyslipidemia management. Meta-regression showed every extra weekly aerobic session reduced TC - 7.68 mg/dL and for every extra week of training by - 0.5 mg/dL. Each minute of session time produced an additional 2.11 mg/dL HDL increase.

CONCLUSION

TSA analysis revealed sufficient data exist to confirm ExTr will improve all five lipid outcomes. CT is optimal for lipid management. The modest effect observed may moderate dyslipidemia medication for primary prevention. Prediction intervals suggest TC, HDL, LDL and TGD are only improved in one-quarter of studies.

Effect of aerobic exercise on bone health in postmenopausal women with obesity: Balancing benefits with caloric restriction and resistance exercise

The decline in bone mineral density (BMD) poses a significant concern for postmenopausal women with obesity. Research indicates that aerobic exercises show potential for enhancing bone health. However, there remains no consensus regarding their effects on BMD. This study aimed to evaluate the effect of various exercise interventions on BMD and overall health among postmenopausal women with obesity, with particular attention to caloric restriction (CR). Following Preferred Reporting Items for Systematic Reviews and Meta-Analyses 2020 guidelines, we performed a comprehensive literature search on PubMed, targeting studies published up to August 2023. Our search focused on aerobic exercise, resistance training, and combined exercise modalities, examining their impact on BMD, body composition, and physical fitness in postmenopausal women with obesity. We reviewed 11 studies, predominantly on aerobic exercise, involving women who are overweight and sedentary, nine of which were randomized trials. Our findings suggest that aerobic exercise has a mild protective effect on BMD and can significantly reduce fat mass. Notably, when combined with CR, aerobic exercise not only enhances the reduction of fat tissue mass but also potentially offers a certain level of protection for BMD. Additionally, the intervention combining aerobic exercise with resistance training emerges as a key promoter of bone health, underscoring the importance of tailored exercise programs for this population. Consequently, balanced dietary patterns (like the Mediterranean diet), combined with exercise, are recommended for optimal health outcomes. Tailored exercise programs integrating both aerobic and resistance training are crucial for sustaining overall health and bone density in this population.

The Influence of Energy Balance and Availability on Resting Metabolic Rate: Implications for Assessment and Future Research Directions

Resting metabolic rate (RMR) is a significant contributor to an individual's total energy expenditure. As such, RMR plays an important role in body weight regulation across populations ranging from inactive individuals to athletes. In addition, RMR may also be used to screen for low energy availability and energy deficiency in athletes, and thus may be useful in identifying individuals at risk for the deleterious consequences of chronic energy deficiency. Given its importance in both clinical and research settings within the fields of exercise physiology, dietetics, and sports medicine, the valid assessment of RMR is critical. However, factors including varying states of energy balance (both short- and long-term energy deficit or surplus), energy availability, and prior food intake or exercise may influence resulting RMR measures, potentially introducing error into observed values. The purpose of this review is to summarize the relationships between short- and long-term changes in energetic status and resulting RMR measures, consider these findings in the context of relevant recommendations for RMR assessment, and provide suggestions for future research.

The effects of breaking sedentary time with different intensity exercise bouts on energy metabolism: A randomized cross-over controlled trial

BACKGROUND AND AIMS

Breaking up sedentary periods, particularly with light activity, increases total energy expenditure (EE), and helps provide better glycemic control. However, the effects of activities of various intensities to interrupt prolonged sedentary time are unclear. The purpose of the present study was to examine potential differences in glycemic control and EE from breaking up sedentary time with short exercise bouts of different intensities.

METHODS AND RESULTS

Nine overweight/obesity young men underwent whole body indirect calorimetry at 19:00 on day 1 and stayed overnight. After awakening on day 2, they performed short duration jogging every 30 min over 8 h (16-time bouts in total) under 3 different conditions with the same running distance: (1) lactate threshold (LT) for 2 min, (2) 60% LT for 200 s, and (3) onset of blood lactate accumulation (OBLA) for 75 s. The 24-h EE and interstitial glucose concentration (from 8:00 to 19:00 on day 2) was continuously measured throughout the trials. The standard deviation during intervention and indexes of postprandial of the interstitial glucose concentration was significantly lower at LT and OBLA than at 60% LT (p < 0.05). The 24-h EE was not significantly different among conditions, but EE at OBLA during intervention was slightly but significantly higher than at 60% LT and LT.

CONCLUSION

Breaking up sedentary time with short-duration jogging at LT and with OBLA intensities may have better glycemic control and increased use of carbohydrate as a fuel, while short-duration a jogging at OBLA intensity may increase EE.

TRIAL REGISTRATION

UMIN000041361.

Resting Energy Expenditure of Physically Active Boys in Southeastern Poland-The Accuracy and Validity of Predictive Equations

Optimization of energy intake in the diet of young athletes is of primary importance. In addition to the energy expenditure associated with their body development, the demand resulting from intensive physical activity also increases. The aim of this study was to compare the accuracy of formulas commonly used for resting energy expenditure (REE) calculations with values obtained from measurements using indirect calorimetry among male children and adolescents practicing football. The study was conducted among 184 boys aged 9 to 17 using a calorimeter and a device for assessing body composition by means of electrical bioimpedance using a segment analyzer. The mean error ranged from −477 kcal/d by the Maffeis formula to −182 kcal/d for the Institute of Medicine of the National Academies (IMNA) formula. A statistically significant difference was found for all formulas in the calculated value in relation to the measured REE value (p < 0.0001). Most “ready-to-use” formulas underestimate REE, which can be a risk in determining the total energy demand in a group that requires more calories, especially when due to intensive growth and development and the expenditure associated with regular training and increased physical activity.

The effect of exercise interventions on resting metabolic rate: A systematic review and meta-analysis

The systematic review and meta-analysis evaluated the effect of aerobic, resistance and combined exercise on RMR (kCal·day^-1) and performed a methodological assessment of indirect calorimetry protocols within the included studies. Subgroup analyses included energy/diet restriction and body composition changes. Randomized control trials (RCTs), quasi - RCTs and cohort trials featuring a physical activity intervention of any form and duration excluding single exercise bouts were included. Participant exclusions included medical conditions impacting upon RMR, the elderly (≥65 years of age) or pregnant, lactating or post-menopausal women. The review was registered in the International Prospective Register of Systematic Reviews (CRD 42,017,058,503). 1669 articles were identified; 22 were included in the qualitative analysis and 18 were meta-analysed. Exercise interventions (aerobic and resistance exercise combined) did not increase resting metabolic rate (mean difference (MD): 74.6 kCal·day^-1[95% CI: -13.01, 161.33], P = 0.10). While there was no effect of aerobic exercise on RMR (MD: 81.65 kCal·day^-1[95% CI: -57.81, 221.10], P = 0.25), resistance exercise increased RMR compared to controls (MD: 96.17 kCal·day^-1[95% CI: 45.17, 147.16], P = 0.0002). This systematic review effectively synthesises the effect of exercise interventions on RMR in comparison to controls; despite heterogenous methodologies and high risk of bias within included studies.

Tabata-style functional exercise increases resting and postprandial fat oxidation but does not reduce triglyceride concentrations

NEW FINDINGS

What is the central question of this study? What are the metabolic impacts of high intensity functional Tabata exercise? What is the main finding and its importance? Tabata exercise with high intensity functional movements causes increases in fasted and postprandial fat oxidation the day after exercise without altering postprandial triglyceride concentrations. These results support the usage of a Tabata-style high intensity functional exercise to improve postprandial fat oxidation.

ABSTRACT

We evaluated the effect of a high fat meal with and without prior high intensity functional exercise executed in a Tabata-style interval pattern on resting and postprandial substrate oxidation, as well as postprandial blood glucose and triglyceride concentrations. Eleven healthy males completed two trials (Tabata exercise (TE) and non-exercise control (CON)) in random order separated by 7 days. A two-day protocol was used in which TE or CON was performed on the first day and a high fat meal was administered ∼13 h later the following morning. Power output from the TE session was quantified using a kinematic approach by calculating external work performed per unit time for each of the four exercises (rowing, dumbbell thrusters, kettlebell swings and burpees). For the meal challenge, respiratory gases and blood samples were taken fasted and at 1, 2 and 3 h postprandial. Fat oxidation was significantly higher after TE compared to CON at all time points (P < 0.05). Carbohydrate oxidation was significantly lower after TE compared to CON at 1 h postprandial (P < 0.05). There were no significant effects of TE on fasting or postprandial glucose or triglyceride concentrations. Functional exercises performed in a high intensity TE pattern enhance fasting and postprandial fat oxidation on the following day with minimal influence on blood triglycerides or glucose levels.

Adaptive thermogenesis and changes in body composition and physical fitness in army cadets

BACKGROUND

To analyze the association between a 34-week military training on body composition, physical fitness and compensatory changes in resting energy expenditure (REE) recognized as adaptive thermogenesis (AT). We also explored if regional body composition changes were related to AT.

METHODS

Twenty-nine male army cadets, aged 17 to 22 years were tested at baseline (T0) and after 34-weeks military training (T1). Physical training was performed 5 days/week during 90 minutes/day. Measurements included body composition by dual-energy x-ray absorptiometry; physical fitness by 3000-m running, pull-up, 50-m freestyle swimming, push-up and sit-up tests; REE measured by indirect calorimetry (REEm) and predicted from fat-free mass (FFM), fat mass (FM) and ethnicity at T0 (REEp). %AT was calculated using values at T1: 100(REEm/REEp-1); and AT (kcal/day) as %AT/100 multiplied by baseline REEm.

RESULTS

Physical training was associated with increases of lean soft tissue (LST) (∆1.2±1.3 kg), FM (∆1.4±1.3 kg), FFM (∆1.2±1.3 kg) and physical fitness (P<0.01), but no REE changes (∆59.6±168.9 kcal/day) and AT were observed (P>0.05). Though a large variability was found, AT was partially explained by trunk LST (r2=0.17, P=0.027). Individuals showing a higher AT response demonstrated a higher trunk LST increase (∆0.8±0.7 kg, P<0.05).

CONCLUSIONS

The military training increased LST, FM, FFM and physical fitness. Though no mean changes in AT occurred, a large individual variability was observed with some participants increasing REE beyond the expected body composition changes, suggesting a spendthrift phenotype. Changes of trunk LST may play an important role in the AT response observed in these individuals.

How much exercise should be promoted to raise total daily energy expenditure and improve health?

Despite longstanding recognition of the benefits of a physically active lifestyle, there remains ambiguity regarding exactly how much exercise should be promoted to raise total energy expenditure (TEE) and improve health. This review provides a brief summary of the dose-response relationship between physical activity and relative risk of morbidity and mortality; mechanisms through which exercise drives an increase in TEE; the highest reported levels of TEE measured via doubly labelled water; and the potential impact of non-compliance and confounders in moderating the contribution of exercise to increase TEE. Cohort studies provide a compelling argument that 'more is better' regarding the exercise dose for increasing TEE, that increasing TEE is protective for health, and that this is mediated through increased cardiorespiratory fitness. However, growing evidence shows that ever increasing volumes of weekly physical activity may reverse the cost-benefit seen with more modest doses. Animal and human studies show that the elevation in TEE associated with increasing exercise volume is commonly less than expected, due to physiological confounders. Further, there is considerable evidence of behavioural non-compliance to planned exercise in all but the most highly motivated athletes. Therefore, inbuilt defence mechanisms may safeguard against TEE being elevated to maximum levels.

Racial Differences in Relative Skeletal Muscle Mass Loss During Diet-Induced Weight Loss in Women

OBJECTIVE

It is unclear whether there are race-specific differences in the maintenance of skeletal muscle during energy restriction. Changes in relative skeletal muscle index (RSMI; limb lean tissue divided by height squared) were compared following (1) diet alone, (2) diet + aerobic training, or (3) diet + resistance training.

METHODS

Overweight, sedentary African American (AA; n = 72) and European American (EA; n = 68) women were provided an 800-kcal/d diet to reduce BMI < 25 kg/m2 . Regional fat-free mass was measured with dual-energy x-ray absorptiometry. Steady-state VO2 and heart rate responses during walking were measured.

RESULTS

AA women had greater RSMI and preserved RSMI during diet alone, while RSMI was significantly reduced among EA women (EA women -3.6% vs. AA women + 1.1%; P < 0.05). Diet + resistance training subjects retained RSMI (EA women + 0.2% vs. AA women + 1.4%; P = 50.05), whereas diet + aerobic training subjects decreased RSMI (EA women -1.4% vs. AA women -1.5%; P < 0.05). Maintenance of RSMI was related to delta walking ease and economy.

CONCLUSIONS

Compared with AA women, EA women are less muscular and lose more muscle during weight loss without resistance training. During diet-induced weight loss, resistance training preserves skeletal muscle, especially among premenopausal EA women. Maintenance of muscle during weight loss associates with better ease and economy of walking.

Why intensity is not a bad word: Optimizing health status at any age

Age-related declines in health and function make locomotion increasingly difficult leading to reductions in non-exercise activity thermogenesis (NEAT), skeletal muscle size and strength, and increased adiposity. Exercise is an important strategy to attenuate loss of function through the life cycle. Despite claims to the contrary, high-intensity exercise is important for the prevention of obesity and sarcopenia with advancing age. Therefore, the purpose of this mini-review is to present literature supporting the contention that low volume, high-intensity aerobic and/or resistance training can slow sarcopenia, sustain ease of movement, stimulate NEAT, and attenuate the accretion of fat mass.

Cardiorespiratory Fitness and Body Composition Responses to Different Intensities and Frequencies of Exercise Training in Colorectal Cancer Survivors

INTRODUCTION

Deteriorations in cardiorespiratory fitness (V˙o_2peak) and body composition are associated with poor prognosis after colorectal cancer treatment. However, the optimal intensity and frequency of aerobic exercise training to improve these outcomes in colorectal cancer survivors is unknown.

PATIENTS AND METHODS

This trial compared 8 weeks of moderate-intensity continuous exercise (MICE; 50 minutes; 70% peak heart rate [HR_peak]; 24 sessions), with high-intensity interval exercise (HIIE; 4 × 4 minutes; 85%-95% HR_peak) at an equivalent (HIIE; 24 sessions) and tapered frequency (HIIE-T; 16 sessions) on V˙o_2peak and on lean and fat mass, measured at baseline, 4, 8, and 12 weeks.

RESULTS

Increases in V˙o_2peak were significantly greater after both 4 (+3.0 mL·kg^-1·min^-1, P = .008) and 8 (+2.3 mL·kg^-1·min^-1, P = .049) weeks of HIIE compared to MICE. After 8 weeks, there was a significantly greater reduction in fat mass after HIIE compared to MICE (-0.7 kg, P = .038). Four weeks after training, the HIIE group maintained elevated V˙o_2peak (+3.3 mL·kg^-1·min^-1, P = .006) and reduced fat mass (-0.7 kg, P = .045) compared to the MICE group, with V˙o_2peak in the HIIE-T also being superior to the MICE group (+2.8 mL·kg^-1·min^-1, P = .013).

CONCLUSION

Compared to MICE, HIIE promotes superior improvements and short-term maintenance of V˙o_2peak and fat mass improvements. HIIE training at a reduced frequency also promotes maintainable cardiorespiratory fitness improvements. In addition to promoting accelerated and superior benefits to the current aerobic exercise guidelines, HIIE promotes clinically relevant improvements even with a substantial reduction in exercise training and for a period after withdrawal.

Potential Causes of Elevated REE after High-Intensity Exercise

INTRODUCTION

Resting energy expenditure (REE) increases after an intense exercise; however, little is known concerning mechanisms.

PURPOSE

The purpose of this study was to determine effects of a single bout of moderate-intensity continuous (MIC) aerobic exercise, or high-intensity interval (HII) exercise on REE under energy balance conditions.

METHODS

Thirty-three untrained premenopausal women were evaluated at baseline, after 8-16 wk of training, 22 h after either MIC (50% peak V˙O2) or HII (84% peak V˙O2). Participants were in a room calorimeter during and after the exercise challenge. Food intake was adjusted to obtain energy balance across 23 h. REE was measured after 22 h after all conditions. Twenty-three-hour urine norepinephrine concentration and serum creatine kinase activity (CrKact) were obtained. Muscle biopsies were obtained in a subset of 15 participants to examine muscle mitochondrial state 2, 3, and 4 fat oxidation.

RESULTS

REE was increased 22 h after MIC (64 ± 119 kcal) and HII (103 ± 137 kcal). Markers of muscle damage (CrKact) increased after HII (9.6 ± 25.5 U·L) and MIC (22.2 ± 22.8 U·L), whereas sympathetic tone (urine norepinephrine) increased after HII (1.1 ± 10.6 ng·mg). Uncoupled phosphorylation (states 2 and 4) fat oxidation were related to REE (r = 0.65 and r = 0.55, respectively); however, neither state 2 nor state 4 fat oxidation increased after MIC or HII. REE was not increased after 8 wk of aerobic training when exercise was restrained for 60 h.

CONCLUSIONS

Under energy balance conditions, REE increased 22 h after both moderate-intensity and high-intensity exercise. Exercise-induced muscle damage/repair and increased sympathetic tone may contribute to increased REE, whereas uncoupled phosphorylation does not. These results suggest that moderate- to high-intensity exercise may be valuable for increasing energy expenditure for at least 22 h after the exercise.

Exercise Training and Energy Expenditure following Weight Loss

PURPOSE

This study aims to determine the effects of aerobic or resistance training on activity-related energy expenditure (AEE; kcal·d(-1)) and physical activity index (activity-related time equivalent (ARTE)) following weight loss. It was hypothesized that weight loss without exercise training would be accompanied by decreases in AEE, ARTE, and nontraining physical activity energy expenditure (nonexercise activity thermogenesis (NEAT)) and that exercise training would prevent decreases in free-living energy expenditure.

METHODS

One hundred forty premenopausal women had an average weight loss of 25 lb during a diet (800 kcal·d(-1)) of furnished food. One group aerobically trained 3 times per week (40 min·d(-1)), another group resistance-trained 3 times per week (10 exercises/2 sets × 10 repetitions), and the third group did not exercise. Dual-energy x-ray absorptiometry was used to measure body composition, indirect calorimetry was used to measure resting energy expenditure (REE) and walking energy expenditure, and doubly labeled water was used to measure total energy expenditure (TEE). AEE, ARTE, and nontraining physical activity energy expenditure (NEAT) were calculated.

RESULTS

TEE, REE, and NEAT all decreased following weight loss for the no-exercise group, but not for aerobic and resistance trainers. Only REE decreased in the two exercise groups. Resistance trainers increased ARTE. HR and oxygen uptake while walking on the flat and up a grade were consistently related to TEE, AEE, NEAT, and ARTE.

CONCLUSIONS

Exercise training prevents a decrease in energy expenditure, including free-living energy expenditure separate from exercise training, following weight loss. Resistance training increases physical activity, whereas economy/ease of walking is associated with increased TEE, AEE, NEAT, and ARTE.

The contribution of fat-free mass to resting energy expenditure: implications for weight loss strategies in the treatment of adolescent obesity

Owing to the strong relationship between fat-free mass (FFM) and resting energy expenditure (REE), the preservation of FFM is often emphasized in the treatment of adolescent obesity. Typical treatment regimens including an increased dietary consumption of protein and participation in resistance training are common components of adolescent weight management programs, despite limited evidence of a positive influence of FFM on weight loss outcomes in adolescents. Given the larger volume of FFM in obese relative to normal weight adolescents and the common treatment goals of both maximizing weight loss and attenuating the loss of FFM, a better understanding of the influence of FFM on energy balance is needed to determine whether strategies to preserve lean tissue or maximize absolute weight loss should be most emphasized. We review the associations among FFM, REE, and weight loss outcomes, focusing on how these relationships might influence energy balance in obese adolescents.

The association between different types of exercise and energy expenditure in young nonoverweight and overweight adults

With decades of trends for decreasing activity during work and travel, exercise becomes an important contributor to total physical activity (PA) and energy expenditure. The purpose of this study was to examine the contribution of different types of exercise to the variability in energy expenditure and time spent at different PA intensities in young adults. Four hundred and seventeen adults (49.9% male; 46.2 overweight/obese) between 21 and 36 years of age provided valid objective PA and energy expenditure data, assessed via the SenseWear Armband (BodyMedia Inc.). Frequency and duration of participation in various exercise types was self-reported. Weight status was based on body mass index (BMI) (kg/m(2)) with body weight and height being measured according to standard procedures. Eighty-four percent of the participants reported regular exercise engagement with no difference in participation rate by sex or BMI category. Exercise time along with sex and ethnicity explained roughly 60% of the variability in total daily energy expenditure (TDEE) while the association between exercise and time spent in moderate to vigorous PA or being sedentary was low or nonsignificant. Engagement in endurance exercise and sports contributed predominantly to the variability in energy expenditure and PA in nonoverweight participants. In overweight/obese participants engagement in resistance exercise and swimming contributed significantly to variability in TDEE. Current exercise recommendations focus primarily on aerobic exercise, but results of the present study suggest that nonweight-bearing exercises, such as resistance exercise and swimming, contribute significantly to the variability in TDEE in overweight/obese adults, which would make these types of activities viable options for exercise interventions.

Lift weights to fight overweight

Although resistance training (RT) has long been accepted as a means for developing and maintaining muscular strength, endurance, power and muscle mass, its beneficial relationship with health factors and chronic disease has only recently been recognized in the scientific literature. Prior to 1990, resistance training was not a part of the recommended guidelines for exercise training and rehabilitation for either the American Heart Association or the American College of Sports Medicine (ACSM). In 1990, the ACSM recognized resistance training as a significant component of a comprehensive fitness programme for healthy adults of all ages, a position subsequently confirmed few years after. At present, even though interest in clinical applications of RT is increasing, there are still some concerns, among physicians, about the use of this exercise methodology in weight control programmes. This review aims to explore the metabolic effects of RT and its efficacy and feasibility in overweight subjects.

Insulin sensitivity affects propensity to obesity in an ethnic-specific manner: results from two controlled weight loss intervention studies

Background

Risk for obesity differs with ethnicity/race and is associated with insulin sensitivity (S_I), insulin responsiveness, and dietary glycemic load (GL). The objective of this study was to test the hypotheses that, 1) obesity-prone, normal weight, African-American (AA) women would be more insulin sensitive than BMI-matched, never overweight AA women; 2) increased adiposity over time would be associated with greater baseline S_I and higher dietary GL in AA but not European-American (EA) women; and 3) increased adiposity over time would be predicted by S_I in women with high but not low acute insulin response to glucose (AIRg).

Methods

Two controlled weight loss interventions were conducted involving overweight (BMI 25.0-29.9 kg/m²) premenopausal AA and EA women. The first included matching with normal-weight (BMI <25.0 kg/m²) controls following weight loss, and then comparing S_I. The second included a 1-year follow-up of weight-reduced participants to identify predictors of change in %body fat. Main outcome measure in the first study was insulin sensitivity (S_I) as assessed with intravenous glucose tolerance test (IVGTT), and in the second study was change in %fat, as assessed with DXA, over one year. AIRg was assessed during IVGTT, and free-living diet was determined by food record.

Results

In the first study, formerly overweight AA women were 43% more insulin sensitive than BMI-matched never overweight AA (P < 0.05). In the second study, S_I was positively associated with change in %fat over 1 year only in AA women (P < 0.05) and women with high AIRg (P < 0.05). In addition, AA who were insulin sensitive and who consumed a higher GL diet tended to gain greater %fat (P = 0.086 for diet x S_I interaction). In both studies, AA women had higher AIRg (P < 0.001) than EA women.

Conclusions

Formerly overweight (obesity-prone) AA women were more insulin sensitive than never overweight AA women, a quality that may predispose to adiposity, particularly when combined with a high GL diet. This ethnicity/race-specific effect may be due to high insulin responsiveness among AA.

High-Intensity Interval Resistance Training (HIRT) influences resting energy expenditure and respiratory ratio in non-dieting individuals

BACKGROUND

The benefits of exercise are well established but one major barrier for many is time. It has been proposed that short period resistance training (RT) could play a role in weight control by increasing resting energy expenditure (REE) but the effects of different kinds of RT has not been widely reported.

METHODS

We tested the acute effects of high-intensity interval resistance training (HIRT) vs. traditional resistance training (TT) on REE and respiratory ratio (RR) at 22 hours post-exercise. In two separate sessions, seventeen trained males carried out HIRT and TT protocols. The HIRT technique consists of: 6 repetitions, 20 seconds rest, 2/3 repetitions, 20 secs rest, 2/3 repetitions with 2'30″ rest between sets, three exercises for a total of 7 sets. TT consisted of eight exercises of 4 sets of 8-12 repetitions with one/two minutes rest with a total amount of 32 sets. We measured basal REE and RR (TT0 and HIRT0) and 22 hours after the training session (TT22 and HIRT22).

RESULTS

HIRT showed a greater significant increase (p < 0.001) in REE at 22 hours compared to TT (HIRT22 2362 ± 118 Kcal/d vs TT22 1999 ± 88 Kcal/d). RR at HIRT22 was significantly lower (0.798 ± 0.010) compared to both HIRT0 (0.827 ± 0.006) and TT22 (0.822 ± 0.008).

CONCLUSIONS

Our data suggest that shorter HIRT sessions may increase REE after exercise to a greater extent than TT and may reduce RR hence improving fat oxidation. The shorter exercise time commitment may help to reduce one major barrier to exercise.

A qualitative investigation of attitudes towards aerobic and resistance exercise amongst overweight and obese individuals

BACKGROUND

Most people are not meeting the minimal requirements for physical activity participation, particularly people who are overweight or obese. Numerous initiatives have been developed which aim to increase levels of physical activity in this group, yet little is known about their feelings towards different types of exercise. In particular, resistance exercise may offer unique benefits to people seeking to lose weight, yet no study to date has examined views of resistance exercise amongst the overweight and obese. This qualitative study examined the views and attitudes towards aerobic and resistance exercise amongst overweight and obese individuals engaged in a weight management clinic.

METHODS

30 overweight and obese patients comprised of 25 females and 5 males, with a mean age of 40.7 years (SD = 15.2) and mean BMI of 33.8 kg/m2 (SD = 7.9) were recruited from a dietetic clinic to take part in baseline focus groups and interviews to assess their views on physical activity. After selecting and participating in a 12 week aerobic- or resistance-exercise program, the participants took part in follow-up interviews. Thematic analysis was then performed on the transcribed focus group and interview data.

RESULTS

For the overweight and obese women in this study, weight loss was the primary motivation for physical activity participation. Subsequently, these women perceived a failure to lose weight as strongly affecting their motivation to continue or re-engage in physical activity. Only 3 participants selected the resistance exercise option. The view of resistance exercise as a masculine activity was a dominant theme amongst all participants. A lack of knowledge of how to perform certain exercises emerged as a barrier, but was seen by the participants as surmountable given appropriate instruction.

CONCLUSIONS

The females in this study cited weight loss as a primary motivation for physical activity participation. This view must be reconciled with the existing knowledge base of physical activity requirements for successful weight loss and maintenance. Participants in this study had little awareness or experience of resistance exercise, and many were fearful of the potential risks.

A 45-minute vigorous exercise bout increases metabolic rate for 14 hours

INTRODUCTION

The magnitude and duration of the elevation in resting energy expenditure after vigorous exercise have not been measured in a metabolic chamber. This study investigated the effects of inserting a 45-min vigorous cycling bout into the daily schedule versus a controlled resting day on 24-h energy expenditure in a metabolic chamber.

METHODS

Ten male subjects (age = 22-33 yr) completed two separate 24-h chamber visits (one rest and one exercise day), and energy balance was maintained for each visit condition. On the exercise day, subjects completed 45 min of cycling at 57% Wmax (mean ± SD = 72.8% ± 5.8% VO(2)max) starting at 11:00 a.m. Activities of daily living were tightly controlled to ensure uniformity on both rest and exercise days. The area under the energy expenditure curve for exercise and rest days was calculated using the trapezoid rule in the EXPAND procedure in the SAS and then contrasted.

RESULTS

The 45-min exercise bout resulted in a net energy expenditure of 519 ± 60.9 kcal (P < 0.001). For 14 h after exercise, energy expenditure was increased 190 ± 71.4 kcal compared with the rest day (P < 0.001).

CONCLUSIONS

In young male subjects, vigorous exercise for 45 min resulted in a significant elevation in postexercise energy expenditure that persisted for 14 h. The 190 kcal expended after exercise above resting levels represented an additional 37% to the net energy expended during the 45-min cycling bout. The magnitude and duration of increased energy expenditure after a 45-min bout of vigorous exercise may have implications for weight loss and management.

Physical activity fluctuations and body fat during adolescence

OBJECTIVE

The objective of the study was to test the hypothesis that greater fluctuations in physical activity lead to greater increases in body fat during adolescence.

METHODS

Seven hundred fifty-six adolescents in Montreal, Canada, aged 12-13 years at baseline, completed a 7-d physical activity recall questionnaire every 3 months over 5 years. Body mass index (BMI), waist circumference, and triceps and subscapular skinfold thickness were measured at baseline and at the end of follow-up. Subject-specific linear regressions, expressing physical activity as a function of time, were fitted and physical activity fluctuation scores were obtained by averaging the absolute values of regression residuals. The association between body fat after 5 years and the physical activity fluctuation score was assessed in linear regressions adjusting for baseline body fat, average number of physical activity sessions per week, diet and sociodemographic variables.

RESULTS

Among boys, there were statistically significant positive associations between physical activity fluctuation and BMI (β, 95% confidence interval: 0.12, 0.02-0.21) and triceps skinfold (0.40, 0.17-0.63). The associations with waist circumference or subscapular skinfold were not statistically significant (0.22, -0.04-0.49; 0.13, -0.05-0.32, respectively). In girls, there were statistically significant negative associations between physical activity fluctuation and BMI (-0.12, -0.20 to -0.03), waist circumference (-0.54, -0.91 to -0.17), subscapular skinfold (-0.41, -0.56 to -0.26) and triceps skinfold (-0.22, -0.38 to -0.05).

CONCLUSION

Physical activity fluctuations appear to affect body fat during adolescence. Sex-specific interventions may be needed given that greater physical activity fluctuations seem unfavourable for boys and beneficial for girls.

Reproducibility and sensitivity of muscle reoxygenation and oxygen uptake recovery kinetics following running exercise in the field

The purpose of this study was to assess the reliability of postexercise near-infrared spectroscopy (NIRS)-derived measurements and their sensitivity to different exercise intensities in the field. Seventeen athletes (24·1 ± 5·6 year) repeated, on three occasions, two 2-min submaximal shuttle-runs at 40% and 60% of V(IFT) (final speed of the 30-15 intermittent fitness test) and a 50-m shuttle-run sprint (Sprint), with (OCC) or without (CON) repeated transient arterial occlusions of the medial gastrocnemius during the postexercise period. NIRS variables (i.e. oxyhaemoglobin [HbO(2)], deoxyhaemoglobin [HHb] and their difference [Hb(diff)]) were measured continuously for 3 min after each exercise. Half-recovery (½Rec) and mean response (MRT; monoexponential curve fitting) times of muscle reoxygenation and muscle oxygen uptake (mVO(2)) recovery were calculated. Reliability was assessed using the typical error of measurement, expressed as a coefficient of variation (CV). Postexercise recovery of muscle reoxygenation revealed CVs ranging from 16·8% to 37·3%; CV for mVO(2) recovery ranged from 6·2% to 20·9%, with no substantial differences shown between NIRS variables and exercise intensities. While running, intensity did not affect MRT or ½Rec for muscle reoxygenation, and differences were found for mVO(2) recovery (e.g. [Hb(diff)]-mVO(2) MRT = 28·7 ± 5·2, 34·2 ± 5·1 and 37·3 ± 6·2 s for 40%, 60% and Sprint, respectively, P<0·01). To conclude, the kinetics of postexercise NIRS measurements showed CV values ranging from 6% to 37%, with no substantial differences between exercise intensities or NIRS-derived variables. However, exercise intensity did influence mVO(2) recovery kinetics, but not that of muscle reoxygenation in an occlusion-free condition.

Beneficial changes in energy expenditure and lipid profile after eccentric exercise in overweight and lean women

The aim was to compare lean and overweight females in regard to the effects of eccentric exercise on muscle damage indices, resting energy expenditure (REE) and respiratory quotient (RQ) as well as blood lipid and lipoprotein profile. Lean and overweight females (deviated by their body mass index) performed an eccentric exercise session. Muscle damage, energy cost and lipid profile were assessed pre-exercise and up to 72 h post-exercise. After eccentric exercise (i) muscle damage indices were affected more in the overweight subjects compared with the lean subjects; (ii) the elevation of absolute and relative REE was larger and more prolonged in the overweight group compared with the lean group; (iii) after 24 h, RQ had significantly declined, with the overweight subjects exhibiting a larger reduction compared with the lean group; and (iv) the blood lipid profile was favorably modified, with the overweight group exhibiting more favorable responses compared with the lean group. The differences between the lean and the overweight subjects may be partly due to the fact that overweight individuals experienced greater muscle damage than lean individuals. Eccentric exercise may be a promising lifestyle factor to combat obesity and dyslipidemias.

Validity of resting energy expenditure estimated by an activity monitor compared to indirect calorimetry

The use of activity monitors (triaxial accelerometers) to estimate total energy expenditure in kilocalories is dependent on the estimation of resting energy expenditure (REE). However, the REE estimated by activity monitors has not been validated against more precise techniques, such as indirect calorimetry (IC). Therefore, the objective of the present study was to compare REE estimated by the Actical activity monitor (ActMon) to that measured by IC and standard prediction equations of REE. Fifty healthy adults between 18 and 43 years of age were measured for weight and percentage of body fat using a digital scale and bioelectrical impedance. The REE estimated by the ActMon was only 129 kJ/d higher, but not statistically different (P>0·05), than the REE measured with IC. Using multiple linear regression, there was a positive relationship for men, but not for women, between fat mass (kg) and percentage of body fat and the difference in REE estimated by the ActMon compared to IC (P < 0·001). Therefore, in the cohort studied, the use of an activity monitor to estimate REE is valid when compared to IC, but not to a standard prediction equation of REE.