Aerobic power and insulin action improve in response to endurance exercise training in healthy 77-87 yr olds

Cardiorespiratory fitness in early-stage Alzheimer disease

There is an increasing interest in exercise and fitness in Alzheimer disease (AD) given evidence suggesting a role in the maintenance of cognitive health. There is, however, little data on the objective measure of cardiorespiratory fitness in individuals with AD. Thus, we assessed cardiorespiratory fitness in early AD and its relationship with physical activity levels, health markers, and cognitive performance in nondemented (Clinical Dementia Rating 0, n=31) and early-stage AD (Clinical Dementia Rating 0.5 and 1, n=31) participants. Cardiorespiratory fitness was assessed with maximal exercise testing to determine peak oxygen consumption (VOpeak2). Additionally, dual emission x-ray absorptiometry scanning for body composition and glucose tolerance tests were conducted. Despite reductions in physical performance and habitual physical activity levels in early AD, cardiorespiratory fitness (VOpeak2) was comparable in the 2 groups (19.8 in early AD vs. 21.2 mL/kg/min in nondemented, P=0.26). AD participants performed well on treadmill tests with similar levels of perceived exertion, maximal heart rate, and respiratory exchange ratio compared with nondemented individuals. After controlling for age and sex, VOpeak2 was associated with a beneficial glucoregulatory profile and inversely associated with percent body fat, body mass index, and triglycerides. A relationship between cognitive performance measures and VOpeak2 was not apparent. These results suggest that individuals in the early stages of AD have the capacity for maximal exercise testing and have comparable levels of cardiorespiratory fitness as nondemented individuals. Reduced physical activity associated with early AD underscores the need for further defining the role of exercise as a potential therapeutic intervention in the early stages of AD.

Exercise-induced alterations in intramyocellular lipids and insulin resistance: the athlete's paradox revisited

We previously reported an "athlete's paradox" in which endurance-trained athletes, who possess a high oxidative capacity and enhanced insulin sensitivity, also have higher intramyocellular lipid (IMCL) content. The purpose of this study was to determine whether moderate exercise training would increase IMCL, oxidative capacity of muscle, and insulin sensitivity in previously sedentary overweight to obese, insulin-resistant, older subjects. Twenty-five older (66.4 +/- 0.8 yr) obese (BMI = 30.3 +/- 0.7 kg/m2) men (n = 9) and women (n = 16) completed a 16-wk moderate but progressive exercise training program. Body weight and fat mass modestly but significantly (P < 0.01) decreased. Insulin sensitivity, measured using the euglycemic hyperinsulinemic clamp, was increased (21%, P = 0.02), with modest improvements (7%, P = 0.04) in aerobic fitness (Vo2peak). Histochemical analyses of IMCL (Oil Red O staining), oxidative capacity [succinate dehydrogenase activity (SDH)], glycogen content, capillary density, and fiber type were performed on skeletal muscle biopsies. Exercise training increased IMCL by 21%. In contrast, diacylglycerol and ceramide, measured by mass spectroscopy, were decreased (n = 13; -29% and -24%, respectively, P < 0.05) with exercise training. SDH (19%), glycogen content (15%), capillary density (7%), and the percentage of type I slow oxidative fibers (from 50.8 to 55.7%), all P < or = 0.05, were increased after exercise. In summary, these results extend the athlete's paradox by demonstrating that chronic exercise in overweight to obese older adults improves insulin sensitivity in conjunction with favorable alterations in lipid partitioning and an enhanced oxidative capacity within muscle. Therefore, several key deleterious effects of aging and/or obesity on the metabolic profile of skeletal muscle can be reversed with only moderate increases in physical activity.

Ageing and physical activity: evidence to develop exercise recommendations for older adultsThis article is part of a supplement entitled Advancing physical activity measurement and guidelines in Canada: a scientific review and evidence-based foundation for the future of Canadian physical activity guidelines co-published by Applied Physiology, Nutrition, and Metabolism and the Canadian Journal of Public Health. It may be cited as Appl. Physiol. Nutr. Metab. 32(Suppl. 2E) or as Can. J. Public Health 98(Suppl. 2)

An abundance of epidemiological research confirms the benefits of physical activity in reducing risk of various age-related morbidities and all-cause mortality. Analysis of the literature focusing on key exercise variables (e.g., intensity, type, and volume) suggests that the requisite beneficial amount of activity is that which engenders improved cardiorespiratory fitness, strength, power, and, indirectly, balance. Age-related declines in these components are such that physical limitations impinge on functional activities of daily living. However, an exercise programme can minimize declines, thus preventing older adults (age 65+ years) from crossing functional thresholds of inability. Cross-sectional and longitudinal data demonstrate that cardiorespiratory fitness is associated with functional capacity and independence; strength and, importantly, power are related to performance and activities of daily living; and balance-mobility in combination with power are important factors in preventing falls. Exercise interventions have documented that older adults can adapt physiologically to exercise training, with gains in functional capacities. The few studies that have explored minimal or optimal activity requirements suggest that a threshold (intensity) within the moderately vigorous domain is needed to achieve and preserve related health benefits. Thus, physical activity and (or) exercise prescriptions should emphasize activities of the specificity and type to improve components related to the maintenance of functional capacity and independence; these will also delay morbidity and mortality. An appropriate recommendation for older adults includes moderately vigorous cardiorespiratory activities (e.g., brisk walking), strength and (or) power training for maintenance of muscle mass and specific muscle-group performance, as well as “balance-mobility practice” and flexibility (stretching) exercise as needed.

Gait in ageing and associated dementias; its relationship with cognition

The focus of this review is on the close relationship between gait and cognition in ageing and associated dementias. This close relationship is supported by epidemiological studies, clinical studies of older people with and without dementia that focused on the intensity of the physical activity, clinical studies with older persons without dementia examining a relationship between gait and specific cognitive processes, and human and animal experimental studies examining a neural basis for such a relationship. Despite these findings, most studies with patients with dementia focus exclusively on the relationship between cognition and dementia, with relatively few addressing the relationship between gait and dementia. However, subtle disturbances in gait can be observed in ageing and in (preclinical) subtypes of dementia that are not known for prominent motor disturbances, i.e. Mild Cognitive Impairment, Alzheimer's Disease, vascular Cognitive Impairment No Dementia, Subcortical Ischaemic Vascular Dementia, Frontotemporal Mild Cognitive Impairment, and Frontotemporal Dementia, supporting a close relationship between gait and cognition. The relationship between gait and cognition is weakened by the few available intervention studies that examine the effects of walking on cognition in patients with (preclinical) dementia. These studies report equivocal results, which will be discussed. Finally, suggestions for future research will be made.

Biologically relevant sex differences for fitness-related parameters in active octogenarians

The number of elderly people is growing in western populations, but only few maximal performance data exist for people >75 years, in particular for European octogenarians. This study was performed to characterize maximal performance of 55 independently living subjects (32 women, 81.1 +/- 3.4 years; 23 men, 81.7 +/- 2.9 years) with a focus on sex differences. Maximal performance was determined in a ramp test to exhaustion on a bicycle ergometer with ergospirometry, electrocardiogram and blood lactate measurements. Maximal isometric extension strength of the legs (MEL) was measured on a force platform in a seated position. Body composition was quantified by X-ray absorptiometry. In >25% of the subjects, serious cardiac abnormalities were detected during the ramp test with men more frequently being affected than women. Maximal oxygen consumption and power output were 18.2 +/- 3.2 versus 25.9 +/- 5.9 ml min(-1) kg(-1) and 66 +/- 12 versus 138 +/- 40 W for women versus men, with a significant sex difference for both parameters. Men outperformed women for MEL with 19.0 +/- 3.8 versus 13.6 +/- 3.3 N kg(-1). Concomitantly, we found a higher proportion of whole body fat in women (32.1 +/- 6.2%) compared to men (20.5 +/- 4.4%). Our study extends previously available maximal performance data for endurance and strength to independently living European octogenarians. As all sex-related differences were still apparent after normalization to lean body mass, it is concluded that it is essential to differentiate between female and male subjects when considering maximal performance parameters in the oldest segment of our population.

Exercise-induced changes in insulin action and glycogen metabolism in elderly adults

PURPOSE

Although data suggest that physical activity is associated with decreased insulin resistance, recommendations for exercise training are not specific for age or level of obesity. Therefore, we examined the influence of moderate-intensity (50% of VO2max) exercise training (MI) versus high-intensity (75% of VO2max) exercise training (HI) on insulin-stimulated glucose disposal (ISGD) in elderly individuals.

METHODS

Following medical examinations, 21 overweight (body mass index = 29 +/- 1 kg x m(-2)) elderly (74 +/- 1 yr) subjects were randomized to 1) HI, 2) MI, or a 3) nonexercising control group. Subjects enrolled in HI or MI completed a 12-wk exercise training regimen designed to expend 1000 kcal x wk. ISGD was assessed using a hyperinsulinemic, euglycemic clamp pre- and postintervention. ISGD was corrected for hepatic glucose production (glucose Ra) using a constant rate infusion of [6,6-H2]glucose and determined during the last 30 min of the clamp by subtracting glucose Ra from the exogenous glucose infusion rate. Nonoxidative glucose disposal was calculated using indirect calorimetry. Body composition testing was completed using dual energy x-ray absorptiometry.

RESULTS

ISGD increased by approximately 20% with HI (Delta of 1.4 +/- 0.5 mg x kg(-1) FFM.min(-1)). However, ISGD did not change (Delta of -0.4 +/- 0.1 mg x kg(-1) FFM.min(-1)) with MI and was not different (Delta of -0.2 +/- 0.1 mg x kg(-1) FFM.min(-1)) in the control group. Nonoxidative glucose disposal increased with HI (Delta of 1.4 +/- 0.5 mg x kg(-1) FFM.min(-1)), but there was no change in nonoxidative glucose disposal with MI or in the control group. No change in body weight or percentage of body fat was observed in any group.

CONCLUSION

In weight-stable subjects, MI resulted in no change in ISGD, and the improvement in ISGD with HI was completely reliant on improvements in nonoxidative glucose disposal.

Combined lower body endurance and upper body resistance training improves performance and health parameters in healthy active elderly

We investigated the effects of combined lower body (LB) endurance and upper body (UB) resistance training on endurance, strength, blood lipid profile and body composition in active older men. Ten healthy still active men (73+/-4 years, V(O2) peak: 36 (31-41) ml min-1 kg-1) were tested before and after 14 weeks of combined training (3 times week-1). Training consisted of 3x12 min of high intensity interval training on a bicycle for endurance interspersed by 3x12 min of UB resistance exercises. V(O2) peak during leg cycling and arm cranking, isokinetic torque of knee extensor and shoulder abductor and the cross-sectional area (CSA) of several muscles from UB and LB were measured. Sagittal abdominal diameter (SAD) and abdominal fat area were measured on MRI scans. Total body composition was assessed by hydrostatic weighing (HW) and dual-energy X-ray absorptiometry (DEXA). Blood lipid profile was assessed before and after training. By the end of the training period, V(O2) peak (l min-1) increased significantly by 9 and 16% in leg cycling and arm cranking tests, respectively. Maximal isokinetic torque increased both for the knee extensor and shoulder abductor muscle groups. CSA increased significantly in deltoid muscle. Percentage of body fat decreased by 1.3% (P<0.05) and abdominal fat and SAD decreased by 12 and 6%, respectively (P<0.01). There was also a significant decrease in total cholesterol and low-density lipoprotein. Thus, combined LB endurance and UB resistance training can improve endurance, strength, body composition and blood lipid profile even in healthy active elderly.

Gender differences in the decline in aerobic capacity and its physiological determinants during the later decades of life

We investigated the hemodynamic determinants of the age-associated decline in maximal oxygen uptake (V(O2 max)) and the influence of gender on the decline in V(O2 max) and its determinants in old and very old men and women. Sedentary, 60- to 92-yr-old women (n = 71) and men (n = 29), with no evidence of cardiovascular disease, underwent maximal treadmill exercise tests during which V(O2 max) and maximal cardiac output (Q(max)) were determined. V(O2 max) and age were inversely related in both women (-23 +/- 2 ml.min(-1).yr(-1); P < 0.0001) and men (-57 +/- 5 ml.min(-1).yr(-1); P < 0.0001). The absolute slope of the V(O2 max) vs. age relationship was twofold steeper in men than in women (P < 0.0001). Q(max) was also inversely related to age in a gender-specific manner (women = -87 +/- 25 ml.min(-1).yr(-1), P = 0.0009; men = -215 +/- 50 ml.min(-1).yr(-1), P = 0.0002; P = 0.01 women vs. men). Age-related changes in maximal exercise arteriovenous oxygen content difference (a-vD(O2)) were marginally different (P = 0.08) between women (-0.12 +/- 0.03 ml.dl(-1).yr(-1), P = 0.0003) and men (-0.22 +/- 0.04 ml.dl(-1).yr(-1), P < 0.0001). Age-associated decreases in Q(max) and a-vD(O2) contributed equally to the declines in V(O2 max) in both men and women. In the later stages of life, V(O2 max), Q(max), and a-vD(O2) decrease with age more rapidly in older men than they do in older women. As a result, the gender differences dissipate in the later decades of life. Declines in Q(max) and a-vD(O2) contribute equally to the age-related decrease in V(O2 max) in men and women.

Exercise and improved insulin sensitivity in older women: evidence of the enduring benefits of higher intensity training

Few studies have compared the relative benefits of moderate- vs. higher intensity exercise training on improving insulin sensitivity in older people while holding exercise volume constant. Healthy older (73 ± 10 yr) women ( N = 25) who were inactive, but not obese, were randomized into one of three training programs (9-mo duration): 1) high-intensity [80% peak aerobic capacity (V̇o2 peak); TH] aerobic training; 2) moderate-intensity (65% V̇o2 peak; TM) aerobic training; or 3) low-intensity (stretching) placebo control (50% V̇o2 peak; CTB). Importantly, exercise volume (300 kcal/session) was held constant for subjects in both the TH and the TM groups. V̇o2 peak was determined by using a graded exercise challenge on a treadmill. Total body fat and lean mass were determined with dual-energy X-ray absorptiometry. The rate of insulin-stimulated glucose utilization as well as the suppression of lipolysis were determined ∼72 h after the final exercise bout by using a two-step euglycemic-hyperinsulinemic clamp. We observed improved glucose utilization at the higher insulin dose with training, but these improvements were statistically significant only in the TH (21%; P = 0.02) compared with the TM (16%; P = 0.17) and CTB (8%; P = 0.37) groups and were observed without changes in either body composition or V̇o2 peak. Likewise in the TH group, we detected a significant improvement in insulin-stimulated suppression (%) of adipose tissue lipolysis at the low-insulin dose (38–55%, P < 0.05). Our findings suggest that long-term higher intensity exercise training provides more enduring benefits to insulin action compared with moderate- or low-intensity exercise, likely due to greater transient effects.

Hormone and Lipolytic Responses to Whole Body Vibration in Young Men

This study examined the effects of whole-body vibration (WBV) on the hormone and lipolytic responses. Eight male subjects performed WBV and control (CON) trials on separate days. The WBV session consisted of 10 sets of vibration for a duration of 60 s with rest periods of 60 s between each set (frequency 26 Hz). The subjects maintained a static squat position with knees bent on the platform. In the CON trial, the WBV stimulation was not imposed. Blood samples were collected before both trials and during the recovery period. In the WBV trial, the concentrations of plasma epinephrine (Epi) and norepinephrine (NE) increased immediately after the session (P < 0.05). Serum free fatty acids (FFA) concentration increased significantly at the 150, 180, and 210 min points of the recovery period in the WBV trial (P < 0.01) with the interaction between trial and time (P < 0.01). Serum glycerol showed no significant change in either trial. These results suggest that the WBV session causes secretions of Epi and NE, and it subsequently increases FFA concentration during the recovery period. However, because the FFA response was inconsistent with that of glycerol, we were unable to clarify the effect of WBV exposure on lipolysis.