Robert S. Mazzeo

Exercise and physical activity for older adults

performance. Importantly, reductions in risk factors associated with disease states (heart disease, diabetes, etc.) improve health status and contribute to an increase in life expectancy. Strength training helps offset the loss in muscle mass and strength typically associated with normal aging. Additional benefits from regular exercise include improved bone health and, thus, reduction in risk for osteoporosis; improved postural stability, thereby reducing the risk of falling and associated injuries and fractures; and increased flexibility and range of motion. While not as abundant, the evidence also suggests that involvement in regular exercise can also provide a number of psychological benefits related to preserved cognitive function, alleviation of depression symptoms

Exercise prescription for the elderly: current recommendations.

AbstractThe benefits for elderly individuals of regular participation in both cardiovascular and resistance-training programmes are great. Health benefits include a significant reduction in risk of coronary heart disease, diabetes mellitus and insulin resistance, hypertension and obesity as well as improvements in bone density, muscle mass, arterial compliance and energy metabolism. Additionally, increases in cardiovascular fitness (maximal oxygen consumption and endurance), muscle strength and overall functional capacity are forthcoming allowing elderly individuals to maintain their independence, increase levels of spontaneous physical activity and freely participate in activities associated with daily living. Taken together, these benefits associated with involvement in regular exercise can significantly improve the quality of life in elderly populations. It is noteworthy that the quality and quantity of exercise necessary to elicit important health benefits will differ from that needed to produce significant gains in fitness.This review describes the current recommendations for exercise prescriptions for the elderly for both cardiovascular and strength/resistance-training programmes. However, it must be noted that the benefits described are of little value if elderly individuals do not become involved in regular exercise regimens. Consequently, the major challenges facing healthcare professionals today concern: (i) the implementation of educational programmes designed to inform elderly individuals of the health and functional benefits associated with regular physical activity as well as how safe and effective such programmes can be; and (ii) design interventions that will both increase involvement in regular exercise as well as improve adherence and compliance to such programmes.

Catecholamine responses to acute and chronic exercise

The body can adjust to a variety of stressors (physical activity, environmental, emotional, etc.) that are known to disrupt normal homeostatic conditions. Specific metabolic and physiological adaptations are required for both acute and chronic stimuli. The sympathoadrenal system is essential for such adjustments as they control and regulate a number of key bodily functions. In response to an acute bout of exercise, both central and peripheral alterations are elicited. The extent of these responses is dependent upon exercise intensity, duration, and tissue specificity. Further, endurance training results in adaptations that are tissue specific and enhance the ability for the maintenance of exercise energetics. While a number of markers are frequently used to assess the involvement of the sympathoadrenal response (plasma and tissue norepinephrine and epinephrine levels), it is important to examine more specific variables such as rates of turnover, synthesis and removal, and activity of key enzymes related to catecholamine metabolism.

Carbohydrate dependence during marathon running

To test the hypothesis that marathon running is dependent on lipid oxidation, 12 post-absorptive males (31.9 +/- 2.1 yr) ran a treadmill marathon and substrate utilization was assessed. Subjects were placed into a fast (F < or = 2 hr, 45 min; 73.3% VO2max), or a slow (S < or = 3 hr, 45 min; 64.5% VO2max) marathon group. The day before testing subjects rested, but ate their normal diet. Subjects were tested in the morning after an overnight fast, and only tap water, at a rate of 1 l.h, was ingested during exercise. Blood glucose concentration rose at exercise onset, peaked at approximately an hour, but then decreased over time remaining at or above resting levels. Free fatty acids and glycerol rose continuously. No significant differences in plasma FFA, glycerol, or blood glucose concentrations were observed between F or S groups during the marathon. Mean blood lactate concentration was significantly higher (P < 0.05) in the F (2.1 +/- 0.3 mM) group than the S (1.2 +/- 0.2 mM) during exercise. Mean plasma epinephrine was significantly higher in the F (0.9 +/- 0.2 ng.ml-1) than the S (0.6 +/- 0.2 ng.ml-1) group; norepinephrine was also higher in F (3.9 +/- 1.4 ng.ml-1) than the S (2.5 +/- 0.9 ng.ml-1, P < or = 0.05). Blood lactate and epinephrine concentrations correlated significantly (4r = 0.76 and 0.78 in F and S groups, respectively).(ABSTRACT TRUNCATED AT 250 WORDS)

Exercise economy does not change after acclimatization to moderate to very high altitude

For more than 60 years, muscle mechanical efficiency has been thought to remain unchanged with acclimatization to high altitude. However, recent work has suggested that muscle mechanical efficiency may in fact be improved upon return from prolonged exposure to high altitude. The purpose of the present work is to resolve this apparent conflict in the literature. In a collaboration between four research centers, we have included data from independent high‐altitude studies performed at varying altitudes and including a total of 153 subjects ranging from sea‐level (SL) residents to high‐altitude natives, and from sedentary to world‐class athletes. In study A (n=109), living for 20–22 h/day at 2500 m combined with training between 1250 and 2800 m caused no differences in running economy at fixed speeds despite low typical error measurements. In study B, SL residents (n=8) sojourning for 8 weeks at 4100 m and residents native to this altitude (n=7) performed cycle ergometer exercise in ambient air and in acute normoxia. Muscle oxygen uptake and mechanical efficiency were unchanged between SL and acclimatization and between the two groups. In study C (n=20), during 21 days of exposure to 4300 m altitude, no changes in systemic or leg VO2 were found during cycle ergometer exercise. However, at the substantially higher altitude of 5260 m decreases in submaximal VO2 were found in nine subjects with acute hypoxic exposure, as well as after 9 weeks of acclimatization. As VO2 was already reduced in acute hypoxia this suggests, at least in this condition, that the reduction is not related to anatomical or physiological adaptations to high altitude but to oxygen lack because of severe hypoxia altering substrate utilization. In conclusion, results from several, independent investigations indicate that exercise economy remains unchanged after acclimatization to high altitude.

Spaceflight downregulates antioxidant defense systems in rat liver.

Liver antioxidant enzyme activities, mRNA abundance, and glutathione (GSH) status were investigated in male Sprague-Dawley rats placed in an enclosure module aboard Space Shuttle STS-63 for 8 d (F, n = 6). F animals were compared to rats housed in an enclosure module on the ground (G, n = 9), which simulated the vibration and temperature conditions associated with launch and flight, and rats kept under conventional ground vivarium conditions in individual cages (V, n = 6). Spaceflight significantly decreased catalase, GSH reductase, and GSH sulfur-transferase activities in the liver (p < .05). Neither enzyme activity nor enzyme protein content of Cu-Zn and Mn superoxide dismutase (SOD) was affected by flight. The relative abundance of mRNA for Cu-Zn SOD and catalase was significantly decreased comparing F with G rats (p < .05). Spaceflight resulted in a dramatic decrease of liver GSH, glutathione disulfide, and total GSH contents (p < .01), which were accompanied by a lower gamma-glutamyl transpeptidase activity (p < .05). F rats showed a 47% (p < .05) increase in liver malondialdehyde concentration compared to G and V rats. Liver protein content was not affected by flight. These results indicate that spaceflight can downregulate antioxidant defense capacity and elicit an oxidative stress in the liver.

The influence of exercise and aging on immune function.

Immune function declines significantly with advancing age. While many components of the immune system are adversely affected, T cell-dependent functions are most dramatically compromised. This is most likely a result of involution of the thymus gland known to occur with age. Defects in T cell proliferative capacity/responsiveness, interleukin-2 production and receptor expression, signal transduction, and cytotoxicity are frequently cited problems associated with immunosenescence. The stress imposed by a single bout of exercise elicits a number of cardiovascular, thermoregulatory, and neuroendocrine responses that can directly influence many variables associated with the immune system. Consequently, during exercise, as well as into the subsequent recovery period, immune function can be significantly altered. Further, recent work has shown that as a result of endurance training adaptations in both baseline and exercising immune function can occur. However, extremely little is known regarding the interaction between exercise, aging and the immune system. Given that a number of age-related changes occur in many systems (e.g., neuroendocrine) known to alter immune function both at rest and during exercise, it would be of value to learn the extent to which both acute and chronic exercise influence immune function in the elderly.

Factors influencing excess postexercise oxygen consumption in trained and untrained women

This study investigated the effects of blood lactate and norepinephrine levels and rectal temperature on excess postexercise oxygen consumption (EPOC) following two different exercise intensities. Six trained and seven untrained women each performed two exercise tests, short-term high-intensity exercise ([HI] approximately 80% maximum oxygen consumption [VO2max]) and long-term low-intensity exercise ([LOW] approximately 65% VO2max) until 300 kcal were expended. Rectal temperature, oxygen consumption (VO2), and lactate and norepinephrine levels were monitored at rest, during exercise, and for 60 minutes into recovery. Exercise times averaged 30.0 +/- 4.5 and 23.7 +/- 0.9 minutes in trained women and 45 +/- 3.6 and 30.0 +/- 0.4 minutes in untrained women for LOW and HI, respectively. Rectal temperature, VO2, and lactate and norepinephrine levels were significantly elevated (P < .05) during HI compared with LOW in both groups. VO2 was elevated throughout recovery following LOW and HI in untrained women only. Additionally, VO2 was elevated until minutes 50 and 40 following LOW and HI, respectively, in trained subjects. Rectal temperature returned to resting levels after 30 minutes of recovery following LOW, but remained significantly elevated throughout minute 50 of recovery following HI in trained women. However, values remained significantly elevated throughout recovery following both exercise bouts in untrained subjects. Norepinephrine levels remained elevated above resting levels throughout recovery following HI and until minute 50 following LOW in trained subjects, whereas levels remained elevated for 5 minutes following LOW and 50 minutes following HI in untrained subjects. Lactate levels remained elevated above baseline values throughout recovery following HI and LOW in both groups.(ABSTRACT TRUNCATED AT 250 WORDS)

Adrenergic contribution during acclimatization to high altitude: perspectives from Pikes Peak.

MAZZEO, R.S., and J.T. REEVES. Adrenergic contribution during acclimatization to high altitude: Perspectives from Pikes Peak. Exerc. Sport Sci. Rev., Vol. 31, No. 1, pp. 13–18, 2003. We have examined the sympathoadrenal responses to both acute and chronic high-altitude exposure at the summit of Pikes Peak, CO, in both men and women. A dissociation between the adrenal medullary response (acute) with that of the sympathetic nervous system (chronic) is observed. Both &agr;- and &bgr;-adrenergic contributions to key metabolic and physiologic adjustments to high-altitude exposure are evident.

Endurance Training and Bone Loss in Calcium-Deficient and Ovariectomized Rats

We examined interactions among physical training, estrogen deficiency, and calcium deficiency with respect to the maintenance of femoral bone in five groups of 10 to 11-month-old female Fischer 344 rats: sedentary intact, sedentary ovariectomized, trained intact, trained ovariectomized, and control. All rats, except controls, were maintained on a calcium-deficient diet (0.02%) for 8 weeks, and had lower femoral weight, density, ash weight, and ash weight/volume than control rats. Ovariectomy combined with calcium deficiency decreased bone density more than did calcium deficiency alone. Treadmill training for 8 weeks resulted in an increase in maximal functional capacity, endurance time, heart weight and heart/body weight and attenuated the decrease in femoral density observed when ovariectomy and calcium deficiency both were present such that it was similar to that observed in calcium deficiency alone. We concluded that calcium-deficient ovariectomized rats undergo some of the bone changes characteristic of osteoporosis, and of these changes, a decrease in femoral density was attenuated by endurance training.