**8. Effects of exercise training on thermoregulation in the elderly individuals**

Several longitudinal studies have reported that heat dissipative responses during exercise in a hot environment are enhanced when aerobic training is performed under hot or even cool to thermoneutral conditions by initially sedentary elderly individuals [30, 60, 84] and young individuals [27–29]. Thomas et al. [30] reported that a 16-week aerobic training program increased VO2max by ≥5% and advanced onset of cutaneous vasodilation in response to an increased mean body temperature during exercise in a hot environment (Ta , 36°C) both in young and in elderly individuals. They also suggested that an enhanced sensitivity of the active vasodilator system contributes to the enhanced cutaneous vasodilation [30]. Additionally, Okazaki et al. [84] supported and extended these results by showing that onset of cutaneous vasodilation and sweating responses to an increased Tes during exercise in a warm environment (T<sup>a</sup> , 30°C) were advanced after an 18-week aerobic and resistance training under cool to thermoneutral conditions in initially sedentary elderly individuals. The improvements in VO2max were 20 and 10%, respectively, in each study. However, both studies indicated that the sensitivity of increase in SkBF and sweat rate to an increased mean body temperature or Tes did not increase after training. Further, Okazaki et al. [84] indicated that a diminished increase in PV following training period in elderly individuals was associated with the unchanged sensitivity, by showing a linear correlation between changes in the sensitivities and those in PV following the training period. Similarly, in young individuals, the increase in PV is considered to be the major mechanism which contributed to the improvement of thermoregulatory responses by exercise training as described in the earlier section. This results from increased venous return to the heart by increasing cardiac stroke volume and/or by suppressing baroreflex-induced reduction of skin vasodilation [11]. Additionally, Ho et al. [60] showed that splanchnic and renal vasoconstriction during exercise were increased in young individuals but not in elderly individuals following aerobic training period. Thus, in elderly people, exercise training improved VO2max but generally diminished the enhancement of thermoregulation compared with younger counterparts [60, 84].

Additionally, this enhanced sensitivity associated with a 10% increase in stroke volume during exercise [89]. Consequently, the improved PV expansion response induced by exercise along with post-exercise protein and CHO intake enhances the attenuated increase in cardiovascular and thermoregulatory capacity in elderly individuals compared with young counterparts. Recently, Kataoka et al. [90] reported the similar results in hypertensive elderly individuals (∼160 mmHg for systolic and ∼90 mmHg for diastolic blood pressure at rest) that PV and SkBF response to increased Tes both increased after aerobic training (60–75% of VO2 peak for 60 min/day, 3 days/week, for 8 weeks) with protein (10 g) and CHO (15 g) supplementation. Furthermore, they showed that despite the increased PV, arterial blood pressures rather decreased after

Body Temperature Regulation During Exercise and Hyperthermia in Diabetics

http://dx.doi.org/10.5772/intechopen.74063

99

Recent studies have presented that aerobic training improves cutaneous vasodilation by local mechanisms in aged skin [91]. Black et al. [92] used L-NAME (an NO synthase inhibitor) during acetylcholine infusions to block NO production and demonstrated that, in initially sedentary elderly individuals, increase in vascular responsiveness following 12 and 24 weeks of aerobic training was induced by the increase in action of NO in the skin. There are similar results in a longitudinal study [93] although a cross-sectional study reported no effects [94]. The enhancement of the sweating function in summer occurred later and its reduction in winter occurred earlier, in an elderly group compared with a younger group despite a smaller seasonal variation range [95]. To prevent heat disorders in elderly individuals, it is strongly recommended that they engage in exercise training prior to the summer season. Regular exercise generally improves thermoregulatory capacity alongside VO2max. Protein and CHO intake

training with an increased carotid arterial compliance and baroreflex sensitivity.

after exercise will also enable adequate training adaptations to be achieved.

type 2 diabetics with higher HbA1c before the exercise intervention [97].

**9. Effects of exercise training on thermoregulation in diabetic patients**

The effects of aerobic fitness along with short- and long-term exercise training have been widely studied in the context of glucoregulation in type 2 and type 1 diabetics. The effects of exercise training on glycemic control in type 2 diabetics are well established. A recent metaanalysis by Umpierre et al. [96] reported that structured exercise training (over 12 weeks) consisting of aerobic exercise, resistance training, or a combination is associated with enhanced glycemic control (~0.7% HbA1c reduction) in type 2 diabetics. They also reported that structured exercise training of more than 150 min per week is associated with greater HbA1c reduction (~0.9%) compared to 150 min or less per week [96]. Structured exercise training also has beneficial effects on diabetes-related complications [97]. Greater benefits are apparent in

In healthy individuals, it has been suggested that higher levels of aerobic fitness and/or physically activity improve the capacity to dissipate heat during exercise [98, 99]. A recent study indicated that the age-related decline in aerobic fitness was associated with the decreased whole-body evaporative heat loss during exercise in the heat [100]. Moreover, a group of trained middleaged males (~48 years) exhibited greater whole-body heat loss than an untrained group during exercise [100]. Other studies have also indicated that VO2max decreased ~7% per decade in sedentary, active, and even endurance-trained populations [101]. Despite reports of the relationship

The primary limiting factor for the blunted increase in PV with aerobic training in elderly people is an attenuated increase in Albcont with exercise [35, 84, 85]. Other factors are likely to be a reduced fluid intake after thermal dehydration [38, 58] or water deprivation [86] with aging. Accordingly, enhanced albumin synthesis in the liver in response to exercise is one mechanism of the increased Albcont after aerobic training in the young individuals [39, 40]. In regard to this point, the response to increase Albcont after aerobic training is smaller in the elderly individuals. It may be affected, in part, by the attenuated hepatic albumin synthesis response to exercise [87, 88] due to decreased gene expression with normal aging. However, it is also reasonable that this is caused by insufficient protein intake for albumin synthesis in elderly people. Decreased daily activity with aging may be accustomed to low energy and protein diets in elderly people. Therefore, improvements would occur if substrates for plasma albumin synthesis are given immediately after exercise when albumin synthesis is reportedly enhanced [40, 88]. In this regard, one study showed that when young and elderly individuals ingested placebo (i.e., non-energy ingestion) just after acute high-intensity interval exercise, the ability of recovery of Albcont and PV after exercise was generally blunted in elderly individuals compered to young individuals. In contrast, Albcont and PV recovered more when they consumed a protein and CHO mixture compared to consumed placebo in both individuals [35].

Okazaki et al. [89] further determined the effects of protein and CHO intake just after exercise on PV and thermoregulatory responses during 8 weeks of aerobic training under cool to thermoneutral conditions in elderly individuals. In individuals consuming protein and CHO, Albcont and PV increased by 6%, and these increases were accompanied by enhanced sensitivities of SkBF and sweat rate (18 and 80%, respectively) to increased Tes. In contrast, they remained unchanged in individuals taking the placebo immediately after exercise [89]. Additionally, this enhanced sensitivity associated with a 10% increase in stroke volume during exercise [89]. Consequently, the improved PV expansion response induced by exercise along with post-exercise protein and CHO intake enhances the attenuated increase in cardiovascular and thermoregulatory capacity in elderly individuals compared with young counterparts. Recently, Kataoka et al. [90] reported the similar results in hypertensive elderly individuals (∼160 mmHg for systolic and ∼90 mmHg for diastolic blood pressure at rest) that PV and SkBF response to increased Tes both increased after aerobic training (60–75% of VO2 peak for 60 min/day, 3 days/week, for 8 weeks) with protein (10 g) and CHO (15 g) supplementation. Furthermore, they showed that despite the increased PV, arterial blood pressures rather decreased after training with an increased carotid arterial compliance and baroreflex sensitivity.

VO2max by ≥5% and advanced onset of cutaneous vasodilation in response to an increased

elderly individuals. They also suggested that an enhanced sensitivity of the active vasodilator system contributes to the enhanced cutaneous vasodilation [30]. Additionally, Okazaki et al. [84] supported and extended these results by showing that onset of cutaneous vasodilation and

advanced after an 18-week aerobic and resistance training under cool to thermoneutral conditions in initially sedentary elderly individuals. The improvements in VO2max were 20 and 10%, respectively, in each study. However, both studies indicated that the sensitivity of increase in SkBF and sweat rate to an increased mean body temperature or Tes did not increase after training. Further, Okazaki et al. [84] indicated that a diminished increase in PV following training period in elderly individuals was associated with the unchanged sensitivity, by showing a linear correlation between changes in the sensitivities and those in PV following the training period. Similarly, in young individuals, the increase in PV is considered to be the major mechanism which contributed to the improvement of thermoregulatory responses by exercise training as described in the earlier section. This results from increased venous return to the heart by increasing cardiac stroke volume and/or by suppressing baroreflex-induced reduction of skin vasodilation [11]. Additionally, Ho et al. [60] showed that splanchnic and renal vasoconstriction during exercise were increased in young individuals but not in elderly individuals following aerobic training period. Thus, in elderly people, exercise training improved VO2max but generally diminished the enhancement of thermoregulation compared with younger counterparts [60, 84].

The primary limiting factor for the blunted increase in PV with aerobic training in elderly people is an attenuated increase in Albcont with exercise [35, 84, 85]. Other factors are likely to be a reduced fluid intake after thermal dehydration [38, 58] or water deprivation [86] with aging. Accordingly, enhanced albumin synthesis in the liver in response to exercise is one mechanism of the increased Albcont after aerobic training in the young individuals [39, 40]. In regard to this point, the response to increase Albcont after aerobic training is smaller in the elderly individuals. It may be affected, in part, by the attenuated hepatic albumin synthesis response to exercise [87, 88] due to decreased gene expression with normal aging. However, it is also reasonable that this is caused by insufficient protein intake for albumin synthesis in elderly people. Decreased daily activity with aging may be accustomed to low energy and protein diets in elderly people. Therefore, improvements would occur if substrates for plasma albumin synthesis are given immediately after exercise when albumin synthesis is reportedly enhanced [40, 88]. In this regard, one study showed that when young and elderly individuals ingested placebo (i.e., non-energy ingestion) just after acute high-intensity interval exercise, the ability of recovery of Albcont and PV after exercise was generally blunted in elderly individuals compered to young individuals. In contrast, Albcont and PV recovered more when they consumed a protein and CHO mixture compared to

Okazaki et al. [89] further determined the effects of protein and CHO intake just after exercise on PV and thermoregulatory responses during 8 weeks of aerobic training under cool to thermoneutral conditions in elderly individuals. In individuals consuming protein and CHO, Albcont and PV increased by 6%, and these increases were accompanied by enhanced sensitivities of SkBF and sweat rate (18 and 80%, respectively) to increased Tes. In contrast, they remained unchanged in individuals taking the placebo immediately after exercise [89].

sweating responses to an increased Tes during exercise in a warm environment (T<sup>a</sup>

, 36°C) both in young and in

, 30°C) were

mean body temperature during exercise in a hot environment (Ta

98 Diabetes and Its Complications

consumed placebo in both individuals [35].

Recent studies have presented that aerobic training improves cutaneous vasodilation by local mechanisms in aged skin [91]. Black et al. [92] used L-NAME (an NO synthase inhibitor) during acetylcholine infusions to block NO production and demonstrated that, in initially sedentary elderly individuals, increase in vascular responsiveness following 12 and 24 weeks of aerobic training was induced by the increase in action of NO in the skin. There are similar results in a longitudinal study [93] although a cross-sectional study reported no effects [94].

The enhancement of the sweating function in summer occurred later and its reduction in winter occurred earlier, in an elderly group compared with a younger group despite a smaller seasonal variation range [95]. To prevent heat disorders in elderly individuals, it is strongly recommended that they engage in exercise training prior to the summer season. Regular exercise generally improves thermoregulatory capacity alongside VO2max. Protein and CHO intake after exercise will also enable adequate training adaptations to be achieved.
