Resistance training for health and disease: introduction.
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Health Status↗
Biomedical subjects
W J Evans
Publications and source records attributed to W J Evans.
Exercise training guidelines for the elderly.
UNLABELLED: The capacity of older men and women to adapt to increased levels of physical activity is preserved, even in the most elderly. Aerobic exercise results in improvements in functional capacity and reduced risk of developing Type II diabetes in the elderly. High-intensity resistance training (above 60% of the one repetition maximum) has been demonstrated to cause large increases in strength in the elderly. In addition, resistance training result in significant increases in muscle size in elderly men and women. Resistance training has also been shown to significantly increase energy requirements and insulin action of the elderly. PURPOSE: We have recently demonstrated that resistance training has a positive effect on multiple risk factors for osteoporotic fracture in previously sedentary postmenopausal women. METHODS: Because the sedentary lifestyle of a long-term care facility may exacerbate losses of muscle function, we have applied this same training program to frail, institutionalized elderly men and women. RESULTS: In a population of 100 nursing home residents, a randomly assigned high-intensity strength-training program resulted in significant gains in strength and functional status. In addition, spontaneous activity, measured by activity monitors, increased significantly in those participating in the exercise program whereas there was no change in the sedentary control group. Before the strength training intervention, the relationship of whole body potassium and leg strength was seen to be relatively weak (r2 = 0.29, P < 0.001), indicating that in the very old, muscle mass is an important but not the only determining factor of functional status. CONCLUSIONS: Thus, exercise may minimize or reverse the syndrome of physical frailty, which is so prevalent among the most elderly. Because of their low functional status and high incidence of chronic disease, there is no segment of the population that can benefit more from exercise than the elderly.
Aged↗
Effects of resistance training and chromium picolinate on body composition and skeletal muscle in older men.
The effects of chromium picolinate (CrPic) supplementation and resistance training (RT) on skeletal muscle size, strength, and power and whole body composition were examined in 18 men (age range 56-69 yr). The men were randomly assigned (double-blind) to groups (n = 9) that consumed either 17.8 micromol Cr/day (924 microg Cr/day) as CrPic or a low-Cr placebo for 12 wk while participating twice weekly in a high-intensity RT program. CrPic increased urinary Cr excretion approximately 50-fold (P < 0.001). RT-induced increases in muscle strength (P < 0.001) were not enhanced by CrPic. Arm-pull muscle power increased with RT at 20% (P = 0.016) but not at 40, 60, or 80% of the one repetition maximum, independent of CrPic. Knee-extension muscle power increased with RT at 20, 40, and 60% (P < 0.001) but not at 80% of one repetition maximum, and the placebo group gained more muscle power than did the CrPic group (RT by supplemental interaction, P < 0.05). Fat-free mass (P < 0.001), whole body muscle mass (P < 0.001), and vastus lateralis type II fiber area (P < 0.05) increased with RT in these body-weight-stable men, independent of CrPic. In conclusion, high-dose CrPic supplementation did not enhance muscle size, strength, or power development or lean body mass accretion in older men during a RT program, which had significant, independent effects on these measurements.
Aged↗
Acute hormonal responses to heavy resistance exercise in younger and older men.
The purpose of this investigation was to examine the acute responses of several hormones [total and free testosterone (TT and FT, respectively), adrenocorticotropic hormone (ACTH), cortisol (C), growth hormone (GH), and insulin (INS)] to a single bout of heavy resistance exercise (HRE). Eight younger [30-year (30y) group] and nine older [62-year (62y) group] men matched for general physical characteristics and activity levels performed four sets of ten repetitions maximum (RM) squats with 90 s rest between sets. Blood samples were obtained from each subject via an indwelling cannula with a saline lock pre-exercise, immediately post-exercise (IP), and 5, 15 and 30 min post-exercise. Levels of TT, FT, ACTH, C and lactate significantly increased after HRE for both groups. Pre-HRE pairwise differences between groups were noted only for FT, while post-HRE pairwise differences were found for TT, FT, GH, glucose and lactate. Area under the curve analysis showed that the 30y group had a significantly higher magnitude of increase over the entire recovery period (IP, 5, 15, and 30 min post-exercise) for TT, FT, ACTH and GH. Few changes occurred in the INS response with the only change being that the 62y group demonstrated a decrease IP. Lactate remained elevated at 30 min post-HRE. This investigation demonstrates that age-related differences occur in the endocrine response to HRE, and the most striking changes appear evident in the FT response to HRE in physically active young and older men.
Adrenocorticotropic Hormone↗
The effect of six months training on weight, body fatness and serum lipids in apparently healthy elderly Dutch men and women.
OBJECTIVE: To investigate the effect of a six-months training program on changes in body weight and lipid concentrations, and their interrelationship in elderly people. DESIGN: Intervention study. The elderly subjects were randomly assigned to a control group or one of two supervised aerobic training groups, either all round activities or ergometer cycling, both exercising 3-4 times a week for six months. SUBJECTS: 229 elderly men and women, aged 60-80 y. MEASUREMENTS: Various fatness parameters by anthropometry, serum lipids and peak power output. RESULTS: During the intervention, no significant changes were observed in weight or body fatness in subjects of the training groups. Serum high density lipoprotein (HDL), low density lipoprotein (LDL) and total cholesterol and triglycerides tended to change in a favourable direction in the elderly of the intervention groups, but only triglyceride concentration in women of the cycle ergometer group (mean difference with controls: -0.24 mmol/L, 95% confidence interval (CI): -0.45, -0.03) and total serum cholesterol and HDL-cholesterol concentrations in subjects of the all-round activity group, (-0.32mmol/L, 95% CI: -0.63, -0.01 and -0.15mmol/L, 95% CI -0.25, -0.05, respectively) were significantly reduced as compared to controls. Regression analysis showed that the intervention-control difference in change of all lipids was independent of changes in weight, body fat and previous engagement in sport activity. CONCLUSION: Regular physical exercise in an elderly population resulted in favourable changes in serum lipid concentrations that were not significant, but no change in body weight or fatness. Change in lipid concentration could not be attributed to change in weight or body fat.
Aged↗
Changes in muscle morphology, electromyographic activity, and force production characteristics during progressive strength training in young and older men.
Effects of a 10-week progressive strength training program composed of a mixture of exercises for increasing muscle mass, maximal peak force, and explosive strength (rapid force production) were examined in 8 young (YM) (29+/-5 yrs) and 10 old (OM) (61+/-4 yrs) men. Electromyographic activity, maximal bilateral isometric peak force, and maximal rate of force development (RFD) of the knee extensors, muscle cross-sectional area (CSA) of the quadriceps femoris (QF), muscle fiber proportion, and fiber areas of types I, IIa, IIb, and IIab of the vastus lateralis were evaluated. Maximal and explosive strength values remained unaltered in both groups during a 3-week control period with no training preceding the strength training. After the 10-week training period, maximal isometric peak force increased from 1311+/-123 N by 15.6% (p <.05) in YM and from 976+/-168 N by 16.5% (p <.01) in OM. The pretraining RFD values of 4049+/-791 N*s(-1) in YM and 2526+/-1197 N*s(-1) in OM remained unaltered. Both groups showed significant increases (p < .05) in the averaged maximum IEMGs of the vastus muscles. The CSA of the QF increased from 90.3+/-7.9 cm2 in YM by 12.2% (p <.05) and from 74.7+/-7.8 cm2 in OM by 8.5% (p <.001). No changes occurred in the muscle fiber distribution of type I during the training, whereas the proportion of subtype IIab increased from 2% to 6% (p < .05) in YM and that of type IIb decreased in both YM from 25% to 16% (p < .01) and in OM from 15% to 6% (p < .05). The mean fiber area of type I increased after the 10-week training in YM (p < .001) and OM (p < .05) as well as that of type IIa in both YM (p < .01) and OM (p < .01). The individual percentage values for type I fibers were inversely correlated with the individual changes recorded during the training in the muscle CSA of the QF (r=-.56, p < .05). The present results suggest that both neural adaptations and the capacity of the skeletal muscle to undergo training-induced hypertrophy even in older people explain the gains observed in maximal force in older men, while rapid force production capacity recorded during the isometric knee extension action remained unaltered during the present mixed strength training program.
Adult↗
Age-related differences in the pancreatic beta-cell response to hyperglycemia after eccentric exercise.
Eccentric exercise (ECC) causes muscle damage, insulin resistance, and increased pancreatic beta-cell secretion in young individuals. However, the effects of age on the pancreatic beta-cell response to glucose after ECC are unknown. Hyperglycemic clamps (180 min, 10.0 mM) were performed on eight young (age 22 +/- 1 yr) and eight older (age 66 +/- 2 yr) healthy sedentary males without exercise (CONT) and 48 h after ECC. ECC increased (P < 0.02) muscle soreness ratings and plasma creatine kinase concentrations in both groups. Insulin and C-peptide secretions were similar between young and older subjects during CONT clamps. ECC increased (P < 0.05) first-phase (0-10 min) C-peptide area under the curve in young (4.2 +/- 0.4 vs. 3.7 +/- 0.6 nM . min; ECC vs. CONT, respectively) but not in older subjects (3.2 +/- 0.7 vs. 3.5 +/- 0.7 nM . min; ECC vs. CONT), with significant group differences (P < 0.02). Indeed, ECC repressed (P < 0.05) first-phase peak C-peptide concentrations in older subjects (0. 93 +/- 0.16 vs. 1.12 +/- 0.11 nM; ECC vs. CONT). Moreover, first-phase C-peptide-to-insulin molar ratios suggest age-related differences (P < 0.05) in insulin/C-peptide clearance after ECC. Furthermore, the observed C-peptide response after ECC was related to abdominal adiposity [r = -0.62, P < 0.02, and r = -0.66, P < 0. 006, for first and second (10-180 min) phases, respectively]. In conclusion, older individuals did not exhibit the compensatory increase in beta-cell secretion observed among young individuals after ECC. Thus, with increasing age, the pancreatic beta-cell may be less responsive to the physiological stress associated with ECC.
Activity Cycles↗
A moderate glycemic meal before endurance exercise can enhance performance.
The purpose of this study was to determine whether presweetened breakfast cereals with various fiber contents and a moderate glycemic index optimize glucose availability and improve endurance exercise performance. Six recreationally active women ate 75 g of available carbohydrate in the form of breakfast cereals: sweetened whole-grain rolled oats (SRO, 7 g of dietary fiber) or sweetened whole-oat flour (SOF, 3 g of dietary fiber) and 300 ml of water or water alone (Con). The meals were provided 45 min before semirecumbent cycle ergometer exercise to exhaustion at 60% of peak O2 consumption (VO2peak). Diet and physical activity were controlled by having the subjects reside in the General Clinical Research Center for 2 days before each trial. Blood samples were drawn from an antecubital vein for glucose, free fatty acid (FFA), glycerol, insulin, epinephrine, and norepinephrine determination. Breath samples were obtained at 15-min intervals after meal ingestion and at 30-min intervals during exercise. Muscle glycogen concentration was determined from biopsies taken from the vastus lateralis muscle before the meal and immediately after exercise. Plasma FFA concentrations were lower (P < 0.05) during the SRO and SOF trials for the first 60 and 90 min of exercise, respectively, than during the Con trial. Respiratory exchange ratios were higher (P < 0.05) at 90 and 120 min of exercise for the SRO and SOF trials, respectively, than for the Con trial. At exhaustion, glucose, insulin, FFA, glycerol, epinephrine, and norepinephrine concentrations, respiratory exchange ratio, and muscle glycogen use in the vastus lateralis muscle were similar for all trials. Exercise time to exhaustion was 16% longer (P < 0.05) during the SRO than during the Con trial: 266.5 +/- 13 and 225.1 +/- 8 min, respectively. There was no difference in exercise time for the SOF (250.8 +/- 12) and Con trials. We conclude that eating a meal with a high dietary fiber content and moderate glycemic index 45 min before prolonged moderately intense exercise significantly enhances exercise capacity.
Adult↗
Exercise and the treatment of wasting: aging and human immunodeficiency virus infection.
A common feature of human immunodeficiency virus (HIV) infection and aging is the loss of skeletal muscle mass. Although the causes of this loss of muscle are multifactorial, there may be some shared characteristics to this loss, and therefore common strategies for its prevention or reversal. For example, loss of muscle mass early in life and early in the progression of HIV infection may result from decreased levels of physical activity. The rapid loss of skeletal muscle mass at the end of life (sometimes referred to as failure to thrive syndrome) and in acquired immunodeficiency syndrome (AIDS) patients may also have common cause: cachexia. However, it also must be pointed out that loss of skeletal muscle mass with advancing age also may result from losses of motor units, decreased rate of skeletal muscle protein synthesis, and impaired regulation of appetite. These factors have not been demonstrated to be consequences of HIV infection. The use of exercise to treat the losses of muscle size, strength, and functional capacity holds great promise. Although the losses of muscle with HIV infection may be more rapid and dramatic than those seen with aging, resistance exercise training can attenuate or arrest this loss. In elderly people, resistance exercise has been demonstrated to result in increased nitrogen balance, muscle mass and strength, functional capacity, energy requirements, and when combined with a protein calorie supplement, increased energy intake. The use of resistance exercise in HIV-infected patients may also provide similar results. This review discusses many of the changes in body composition, physiological function, and metabolism associated with aging and HIV infection. The specific effects of exercise in the elderly and in patients infected with HIV on the treatment of muscle wasting, and its consequences are also discussed.
Aging↗
Nutrition, exercise, and healthy aging.
Advancing age is associated with a remarkable number of changes in body composition, including reduction in lean body mass and increase in body fat, which have been well documented. Decreased lean body mass occurs primarily as a result of losses in skeletal muscle mass. This age-related loss in muscle mass has been termed "sarcopenia". Loss in muscle mass accounts for the age-associated decreases in basal metabolic rate, muscle strength, and activity levels, which, in turn are the cause of the decreased energy requirements of the elderly. In sedentary persons, the main determinant of energy expenditure is fat-free mass, which declines by about 15% between the third and eighth decade of life. It also appears that declining energy needs are not matched by an appropriate decline in energy intake, with the ultimate result being increased body fat content. Increased body fatness and increased abdominal obesity are thought to be directly linked to the greatly increased incidence of non-insulin-dependent diabetes mellitus among the elderly. In this review we will discuss the extent to which regularly performed exercise can affect nutrition needs and functional capacity in the elderly. We will also discuss a variety of concerns when prescribing exercise in the elderly, such as planning for a wide variability in functional status, medical status, and training intensity and duration. Finally, we will attempt to provide some basic guidelines for beginning an exercise program for older men and women and establishing community-based programs.
Adult↗
Olfactory event-related potentials to amyl acetate in congenital anosmia.
Olfactory function was evaluated by olfactory event-related potentials and standardized psychophysical measures including the Smell Identification Test and odor detection threshold tests for 3 chemosensory stimulants in 9 subjects with isolated congenital anosmia and 9 age- and gender-matched normosmic controls. There was a significant difference in Smell Identification Test scores (P < 0.001) and odor detection thresholds for phenylethyl alcohol (P < 0.001) and isoamyl acetate (P < 0.001) between the anosmic and normosmic subjects. Detection thresholds for chloracetyl phenone, a trigeminal stimulant, did not differ between the 2 groups. Olfactory evoked potentials were recorded in response to amyl acetate and air control stimuli presented at volume flow rate of 5 l/min, stimulus duration of 40 ms, and randomized interstimulus intervals of 6-30 s. In the control subjects, evoked potentials to amyl acetate were characterized by 4 reproducible components (P1, N1, P2, and N2). In the subjects with congenital anosmia, no reproducible evoked potential components were identified in response to amyl acetate. No reproducible evoked potential components were seen in response to the air control stimulus in either the anosmic or normosmic groups. These data suggest that olfactory evoked potentials provide a specific measure of olfactory function.
Adult↗
Energy requirement for long-term body weight maintenance in older women.
The total dietary energy requirement of healthy, free-living older women was examined by determining the total energy intake (TEI) required for long-term body weight maintenance in nine women aged (mean +/- SD) 67 +/- 9 years (range, 56 to 78). For 14 weeks, each woman consumed defined amounts of foods and beverages prepared at a General Clinical Research Center (GCRC) to provide 0.8 g protein.kg-1.d-1 and a nonprotein energy ratio of 40% fat to 60% carbohydrate. Adjustments to TEI were made to keep body weight within +/-0.5 kg of each woman's starting body weight. All women were asked to maintain their habitual level of daily activity, and the energy cost of physical activity was estimated using the Yale Physical Activity Survey (YPAS). Resting energy expenditure (REE) was measured with each woman in the postabsorptive state just after awakening, using an indirect calorimeter at baseline and week 14. The energy requirement expressed as the ratio of TEI to REE was 1.82 +/- 0.15, a value 21% higher (P < .001) than the energy allowance of 1.5 x REE suggested for women beyond age 50 years in the 1989 Recommended Dietary Allowances (RDAs). Using the RDAs equation to predict REE from body weight (pREE), the ratio of TEI to pREE was 1.73 +/- 0.18 (P < .005, comparison with 1.50 x REE). Estimates of the energy expenditure for physical activity (EEPA) based on the energy intake-balance data and the YPAS data were similar (3.18 +/- 0.92 and 3.14 +/- 1.42 MJ/d, respectively) for the group of women, but were more variable on an individual basis. Results of this long-term energy balance study suggest that the RDAs underestimate the dietary energy requirement of older women.
Aged↗
Aging and the acute phase response to exercise: implications for the role of systemic factors on skeletal muscle protein turnover.
Declines in exercise capacity throughout an individual's life span can affect function and can ultimately limit the ability to perform activities of daily living. Along with these changes in exercise capacity and function, studies have reported age-associated changes in several parameters of immune status including declines in cell-mediated and humoral immunity. Exercise has been shown repeatedly to activate host-specific defense mechanisms in a series of coordinated metabolic events similar to the acute phase response to infection. This review will focus on the role of the acute phase response on skeletal muscle remodeling after exercise. In particular, we will discuss the physiological role of exercise-induced neutrophilia and monocyte production of the cytokine interleukin-1 on skeletal muscle remodeling in young and older individuals. The implications of these responses in mediating the metabolic adaptations to exercise will be addressed.
Acute-Phase Reaction↗
Chromium picolinate supplementation and resistive training by older men: effects on iron-status and hematologic indexes.
Chromium competes with iron for binding to transferrin, and high-dose chromium supplementation has been hypothesized to adversely affect iron status. This study examined the effects of chromium picolinate supplementation on hematologic indexes and selected indexes of iron status in 18 men aged 56-69 y who participated in an introductory resistive training program. The men were randomly assigned (double-blind design) to groups (n = 9) that consumed either 17.8 mumol Cr/d (924 micrograms Cr/d) as chromium picolinate or a low-chromium placebo for 12 wk while engaging in resistive training twice weekly (3 sets of 8-12 repetitions at 80% of one repetition maximum for 5 exercises). Hematocrit, hemoglobin, red blood cell (erythrocyte) count, mean corpuscular volume, mean corpuscular hemoglobin, mean corpuscular hemoglobin concentration, red blood cell distribution width, platelet count, and mean platelet volume were within normal clinical ranges and were unchanged by either chromium picolinate supplementation or resistive training. Resistive training decreased total-iron-binding capacity from 38.4 +/- 9.3 to 27.3 +/- 5.6 mumol/L (P < 0.0001) and increased transferrin saturation from 35.7 +/- 16.3% to 45.4 +/- 16.9% (P = 0.050). Chromium picolinate supplementation did not influence these responses. Serum iron concentrations and serum ferritin concentrations were unchanged by either resistive training or chromium picolinate supplementation. These data suggest that high-dose chromium picolinate supplementation for 12 wk did not influence hematologic indexes or indexes of iron metabolism or status in older men. The decrease in total-iron-binding capacity and increase in transferrin saturation (%) with resistive training are largely opposite to changes associated with iron depletion and suggest a novel effect of resistive training on iron transport.
Aged↗
The reproducibility of the Bruce protocol exercise test for the determination of aerobic capacity in older women.
The reproducibility of the Bruce exercise test protocol for the determination of maximal aerobic activity was evaluated in sedentary older women. Seventeen women between the ages of 51 and 68 yr performed five maximal graded exercise tests to volitional fatigue on a treadmill. VO2max (mL.kg-1.min-1) values averaged 27.5 +/- 1.1; 28.3 +/- 1.3; 28.4 +/- 1.3; 29.6 +/- 1.5; and 28.2 +/- 1.4 for trials 1-5, respectively, and were not significantly different. Criteria for a plateau in VO2 at the point of exhaustion were met in 21 out of 85 tests (25%). The mean coefficient of variation VO2max for the subjects for the 5 tests was 6.5% (range, 2.0-14%). Pearson's correlation coefficients for the study variables were significant, indicating good agreement between repeated tests (r2: between 0.70 to 0.89). Although there were no significant differences among the mean VO2max values in the 5 trials, 11 subjects had a 1.0 ml.kg-1.min-1 or greater increase in the VO2max from test 1 to test 2, and only 6 subjects had no change or a decrease in VO2max. The mean difference between T2 and T3 was lower (T1 vs T2: 0.8 mL.kg-1.min-1, T2 vs T3: 0.1 mL.kg-1.min-1) indicating slightly better agreement between the second and third set. Estimates of the between and within subject variance revealed a low within subject variance (4.2 (mL.kg-1.min-1)2) compared to the between subject variance (22.1 (mL.kg-1.min-1)2). This study demonstrates that a commonly used exercise testing protocol generates highly reproducible measurements of VO2max in women between 51 and 68 yr. The mean differences between tests and the high level of agreement between repeated tests suggests that a single measurement of VO2max can be performed to assess functional aerobic capacity in this population.
Aged↗
Attentional mechanisms of saccadic eye movements in schizophrenia.
Saccadic latency of schizophrenics (N = 15) and normal controls (N = 11) was measured to the left and right visual fields with three fixation conditions that differentially affect saccade latency. Fixation was offset either 1) prior to the target (gap condition), 2) simultaneous with the target onset (control condition), or 3) after target onset (overlap condition). Saccade latencies are typically reduced in the gap condition, which is attributed to the fixation offset acting to facilitate attentional disengagement or as a preparatory warning signal. Repeated measures Analysis of Variance (ANOVA) revealed that whereas the saccadic latencies of schizophrenics and normal controls do not differ for right visual field targets, the schizophrenics' latencies were prolonged to left visual field targets. This difference was most pronounced in the overlap condition, where normal controls produced faster saccades to the left visual field targets, whereas schizophrenics showed the opposite asymmetry. Because the overlap condition provides no early warning of the upcoming target, the lateralized finding suggests a deficit in the right hemisphere mechanisms responsible for sustained attention.
Adolescent↗
Analysis of body-composition techniques and models for detecting change in soft tissue with strength training.
The purpose of this study was to compare the ability of various body-composition assessment techniques to detect changes in soft tissue in older, weight-stable women (50-70 y of age) completing a 1-y randomized, controlled trial of progressive resistance training. The intervention group (n = 20) performed high-intensity strength-training 2 d/wk with five different exercises; the control group (n = 19) was untreated. Hydrostatic weighing, 24-h urinary creatinine, computed tomography of thigh sections, total body potassium, and tritium dilution techniques were used to measure increases in total fat-free mass (FFM) and the muscle and water components of FFM. A decrease in fat mass (by hydrostatic weighing) was seen in the strength-trained women compared with the control subjects (P - 0.01-0.0001). Anthropometry, bioelectric impedance, dual-energy X-ray absorptiometry, and total body nitrogen and carbon did not measure any significant change in soft tissue. The choice of a body-composition technique is important when designing a study expected to affect soft tissue, because not all techniques available are precise enough to detect small changes.
Absorptiometry, Photon↗
Effects of age on energy expenditure and substrate oxidation during experimental overfeeding in healthy men.
Relatively little is known about the influence of age on energy regulation during energy imbalance. We compared the effects of overfeeding on changes in energy expenditure, substrate oxidation, and energy deposition between young men (age 23.7 +/- 1.1 [SEM] years) and older men (age 70.0 +/- 7.0) of normal body weight who were leading unrestricted lives. Changes in total energy expenditure, resting energy expenditure (REE), the thermic effect of feeding (TEF), respiratory quotient (RQ), and body energy content were determined in response to overeating by 4.09 +/- 0.07 Megajoule (MJ)/day for 21 days in 16 healthy subjects consuming a typical diet. After excluding data from one young subject with unusual results and adjusting for individual differences in excess energy intake, there was a tendency towards a smaller increase in REE in older men compared to the young men (p = .07) which was accounted for by their lower fat-free mass (p = .016). There was also a significantly smaller increase in resting energy expenditure averaged over fasting and fed states (i.e, REE + TEF) with overfeeding in older men than in young men (p < .01). Combined, these smaller increases in energy expenditure with overfeeding in the older subjects averaged an estimated 365 kilojoule (kJ)/day (8.9% of the excess energy intake) (p < .02). There were also significant effects of age on fasting RQ (p < .001) and the change in RQ with overfeeding (p < .001), but no significant increase in energy expenditure for physical activity and thermoregulation with overfeeding in either age-group. These results are consistent with the suggestion that older individuals experience both a reduction in the ability to increase energy expenditure, and an alteration in the pattern of substrate utilization, in response to overfeeding. These changes may promote cumulative increases in body energy during normal cycles of positive energy balance unless compensated for by adaptive variations in energy intake.
Adult↗