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Background A sarcopenia diagnosis is confirmed by the presence of low muscle quantity or quality under the 2018 revised definition by the European Working Group on Sarcopenia in Older People 2. Imaging methods [i.e. magnetic resonance imaging (MRI)], dual‐energy X‐ray absorptiometry (DXA), and bioelectrical impedance analysis are tools to evaluate muscle quantity or quality. The present study aimed to investigate whether and how low‐intensity and moderate‐intensity resistance training improved both muscle quantity and quality measured by MRI, DXA, and segmental bioelectrical impedance spectroscopy (S‐BIS) in middle‐aged and older people. Methods A single‐blind, randomized, controlled trial was conducted. Community‐dwelling people aged 50–79 years were randomly allocated to no exercise (no‐Ex), low‐intensity exercise (low‐Ex), and moderate‐intensity exercise (moderate‐Ex) groups. Participants in the exercise groups performed resistance training for 24 weeks, with loads of 40% and 60% of one repetition maximum in the low‐Ex and moderate‐Ex groups, respectively. Cross‐sectional area (CSA), lean mass, and muscle electrical properties on S‐BIS were used to determine the effects of training interventions on muscle quantity and quality of the lower limbs. Results Fifty participants (no‐Ex 17, age 63.5 ± 8.5 years, women 47.1%; low‐Ex 16, age 63.6 ± 8.1 years, women 50.0%; moderate‐Ex 17, age 63.5 ± 8.3 years, women 52.9%) completed the 24 week exercise intervention. For the primary outcome, significant intervention effects were found in thigh muscle CSA on MRI between the moderate‐Ex and no‐Ex groups (+6.8 cm2, P < 0.01). Low‐Ex for 24 weeks only increased quadriceps CSA (+2.3 cm2, P < 0.05). The per cent change of thigh muscle CSA (+7.0%, P < 0.01) after 24 week moderate‐Ex was higher than that of leg lean mass on DXA (+2.3%, P = 0.088). Moderate‐Ex for 24 weeks also improved S‐BIS electrical properties related to muscle quantity and quality, including the intracellular resistance index (+0.1 cm2/Ω, P < 0.05), membrane capacitance (+0.7 nF, P < 0.05), and phase angle (+0.3 deg, P < 0.05); their changes were positively correlated with that of thigh muscle CSA (P < 0.01). Conclusions Resistance exercise with moderate intensity improved muscle quantity and quality measured by MRI and S‐BIS, whereas that with low intensity only increased muscle quantity in middle‐aged and older people. The comparisons among the responses to exercise between the assessment methods indicate the greater value of MRI and S‐BIS to measure changes of muscle quantity and quality than of lean mass measured by DXA for assessing the local effects of resistance training.

Heatstroke is a serious heat-related illness that can even cause death. Heat alert systems play an important role in reducing the number of patients experiencing heat illness, as they encourage preventive actions such as the use of air conditioning, hydration, or other strategies. However, to date, the Japanese hazard classification has not considered seasonal and regional variations, despite clear differences in meteorological conditions across different regions in Japan. Moreover, several studies have reported a difference in thermoregulation between older and younger adults, implying that the hazard classification should also consider age differences. This study examined the relationship between the number of ambulance dispatches related to heat illness (ADRHI) and the Japanese heat hazard classification from 2010 to 2019, focusing on monthly and regional differences. Data from 47 prefectures during the 10-year period were collected and analyzed. ADRHI and wet bulb globe temperature (WBGT) data were collected from Japan’s Ministry of Internal Affairs and Communications and the Ministry of the Environment Heat Illness Prevention Information website, respectively. The findings showed a significant relationship between ADRHI and WBGT max (p < 0.05, r = 0.74). ADRHI per 100,000 people showed significant differences across months. The post hoc test detected the first steep increase in ADRHI at a WBGT max of 23°C than at 22°C in June, and at a WBGT max of 26°C, 27°C, and 25°C in July, August, and September, respectively. Moreover, the first significant increase in ADRHI per 100,000 people at WBGT max differed across each region, at a WBGT max of 24°C in Hokkaido-Tohoku, 25°C in Kanto, Kansai, and Chugoku, 26°C in Chubu, 27°C in Shikoku, and 28°C in Kyushu-Okinawa. Further, Poisson regression analysis revealed that the relative risks differed across each region and month. These results imply that the hazard classification should be adjusted according to region and month in Japan.

In older adults, the quantitative decline of the quadriceps femoris is associated with the augmentation of difficulty in the execution of a stand-up task. However, it is unclear whether the cross-sectional areas (CSAs) of individual thigh muscles differ between older adults who can stand up from a 40-cm-height chair on a single leg and those who cannot. To investigate this, the present study determined the CSAs of individual mid-thigh muscles in 67 Japanese women aged 60–77 years by using a magnetic resonance imaging method. Participants were asked to stand up from a 40-cm-height chair on a single leg, and those who could and could not stand up without leaning back and maintain a standing posture for 3 seconds on a single leg were allocated into the successful group (SG, n = 40) and unsuccessful group (USG, n = 27), respectively. Only the CSA of the adductors (sum of the adductor longus and adductor magnus) was significantly smaller in USG compared to SG. When CSA was expressed relative to the two-third power of body mass, the values for the four heads of the quadriceps femoris and biceps femoris long head, as well as the adductors, were significantly lower in USG than in SG. The current results indicate that in terms of the value relative to body mass, the reduced CSAs of the adductors and biceps femoris long head, as well as the four heads of the quadriceps femoris, are associated with the failure of attempts to stand up from a 40-cm-height chair on a single leg in older women. This may be due to the anatomical function of the two muscle groups, which contributes to hip extension movement involved in transitioning from a sitting position to a standing position during the stand-up task.

In older adults, the quantitative decline of the quadriceps femoris is associated with the augmentation of difficulty in the execution of a stand-up task. However, it is unclear whether the cross-sectional areas (CSAs) of individual thigh muscles differ between older adults who can stand up from a 40-cm-height chair on a single leg and those who cannot. To investigate this, the present study determined the CSAs of individual mid-thigh muscles in 67 Japanese women aged 60-77 years by using a magnetic resonance imaging method. Participants were asked to stand up from a 40-cm-height chair on a single leg, and those who could and could not stand up without leaning back and maintain a standing posture for 3 seconds on a single leg were allocated into the successful group (SG, n = 40) and unsuccessful group (USG, n = 27), respectively. Only the CSA of the adductors (sum of the adductor longus and adductor magnus) was significantly smaller in USG compared to SG. When CSA was expressed relative to the two-third power of body mass, the values for the four heads of the quadriceps femoris and biceps femoris long head, as well as the adductors, were significantly lower in USG than in SG. The current results indicate that in terms of the value relative to body mass, the reduced CSAs of the adductors and biceps femoris long head, as well as the four heads of the quadriceps femoris, are associated with the failure of attempts to stand up from a 40-cm-height chair on a single leg in older women. This may be due to the anatomical function of the two muscle groups, which contributes to hip extension movement involved in transitioning from a sitting position to a standing position during the stand-up task.

We previously reported that ice slurry ingestion reduced forehead skin temperature, thereby potentially reducing brain temperature (T brain ). Therefore, in the current study, we investigated the effect of ice slurry ingestion on T brain using proton magnetic resonance spectroscopy, which is a robust, non-invasive method. Eight male participants ingested 7.5 g/kg of either a thermoneutral drink (37 °C; CON) or ice slurry (−1 °C; ICE) for about 5 min following a 15-min baseline period. Then, participants remained at rest for 30 min. As physiological indices, T brain , rectal temperature (T re ), mean skin temperature, nude body mass, and urine specific gravity were measured. Subjective thermal sensation (TS) and thermal comfort (TC) were measured before and after the experiment. T brain and T re significantly reduced after ingestion of ICE compared with after ingestion of CON, and there was a significant correlation between T brain and T re . The other physiological indices were not significantly different between beverage conditions. TS and TC were significantly lower with ICE than with CON ( p  < 0.05). These results indicate that ice slurry ingestion can cool the brain, as well as the body’s core.

Purpose The present study was performed to determine the impact of hypoxia on working muscle oxygenation during incremental running, and to compare tissue oxygenation between the thigh and calf muscles. Methods Nine distance runners and triathletes performed incremental running tests to exhaustion under normoxic and hypoxic conditions (fraction of inspired oxygen = 0.15). Peak pulmonary oxygen uptake ( V ˙ O 2 peak ) and tissue oxygen saturation (StO 2 ) were measured simultaneously in both the vastus lateralis and medial gastrocnemius. Results Hypoxia significantly decreased peak running speed and V ˙ O 2 peak ( p  < 0.01). During incremental running, StO 2 in the vastus lateralis decreased almost linearly, and the rate of decrease from warm-up (180 m min −1 ) to V ˙ O 2 peak was significantly greater than in the medial gastrocnemius under both normoxic and hypoxic conditions ( p  < 0.01). StO 2 in both muscles was significantly decreased under hypoxic compared with normoxic conditions at all running speeds ( p  < 0.01). The rate at which StO 2 was decreased by hypoxia was greater in the vastus lateralis as the running speed increased, whereas it changed little in the medial gastrocnemius. Conclusions These results suggest that the thigh is more deoxygenated than the calf under hypoxic conditions, and that the effects of hypoxia on tissue oxygenation differ between these two muscles during incremental running.

•A 16-wk resistance exercise training program caused 1.5% muscle hypertrophy (MH).•Daily total protein intake throughout the intervention was not associated with MH.•Protein intake at baseline during breakfast was negatively associated with MH.•Increased protein intake at breakfast during resistance exercise training was positively associated with MH. The aim of this study was to observe the relationship of protein intake at each meal and daily total with change in lean tissue mass with progressive resistance exercise training (RET) in healthy middle-aged women. Twenty-two healthy Japanese women were recruited from Shiga Prefecture, Japan, and a supervised whole body RET program was conducted twice a week for 16 wk. The dietary intake was assessed using 3-d dietary records. Dual-energy x-ray absorptiometry was used to measure the whole body lean soft tissue mass (WLTM). Multiple regression analysis was performed to examine the relationship between the protein intake and RET-induced changes in the WLTM after adjusting for age, sleep quality, physical activity, and energy intake. The 16-wk RET program caused a significant gain in the WLTM (1.46 ± 0.45%, P = 0.004). Multiple regression analysis showed that the baseline protein intake at breakfast was negatively associated with the percent change in the WLTM (β = –1.598; P = 0.022). Additionally, the percent change (β = 0.624; P = 0.018) in protein intake at breakfast was positively associated with the percent change in WLTM. Increasing protein intake at breakfast may contribute to RET-induced muscle hypertrophy in middle-aged women, especially among those who habitually consume low-protein levels at breakfast. However, future studies with larger sample sizes are required to confirm the importance of protein intake at breakfast.

In this study, to examine the effects of the combination of resistance training and high-protein intake on the health status of aged muscles and arteries, we used a lot of materials and methods. [...]due to word count limitations, detailed descriptions of certain methods, such as ultrasound measurements of muscle thickness and echo intensity (EI), were provided in the Supplemental Materials and Methods. Additionally, protein intake, as assessed by a questionnaire-based dietary survey, did not change significantly before and after each intervention, indicating no excessive protein intake during the study. [...]these results suggest that the intervention in this study did not adversely affect renal function. The primary finding of our study is that, for older adults, the combination of moderate to high-intensity resistance training and regular intake of steamed chicken breast as a high-protein food may be a novel exercise and nutritional therapy. Because the diagnostic criteria for sarcopenia primarily focus on lower limb muscle function and mass, improving the lower limbs represents the first strategy for reducing the risks of sarcopenia; therefore, in this study, we employed resistance training targeting the lower limbs.

Background Resistance training is a well‐known exercise therapy for preventing and improving lacks of muscle mass, strength, and quality with advances in age; however, its effects on arterial stiffness are not beneficial. Additionally, a higher intake of protein, which is an effective nutrient for muscle health, results in lower arterial stiffness. Whether the combination of moderate to high‐intensity resistance training and high‐protein intake would improve muscle mass, strength, and quality and cancel the resistance training‐induced increase in arterial stiffness in elderly women remains unclear. Methods Ninety‐three elderly women (67.2 ± 5.3 years) were randomly divided into four groups; sedentary control (CON), higher dietary animal protein intake (HP), resistance training (RT), and combination of RT and HP (RT + HP) groups. Participants in the RT and RT + HP groups completed 12 weeks of resistance training (exercise intensity at 70% of one‐repetition maximum (1‐RM), three sets with 10 repetitions of leg extension and curls, 3 days/week). In addition to the daily diet, the HP and RT + HP groups consumed steamed chicken breast as a high‐protein diet. Results Percent changes in thickness (indices of muscle mass) and echo intensity (index of muscle quality) in the quadriceps muscle, 1‐RM of leg extension and curls (index of muscle strength), and circulating C1q levels (a potential biomarker of muscle fibrosis) in the RT and RT + HP groups significantly improved after both RT and RT + HP interventions (P < 0.05). Percent changes in carotid‐femoral pulse wave velocity (cfPWV) and carotid β‐stiffness (indices of arterial stiffness), and circulating angiotensin II (a vasoconstrictor peptide hormone) levels via each intervention were significantly higher in the RT group (4.9 ± 12.7%, 13.8 ± 13.5%, 94.9 ± 132.7%, respectively), as compared with the CON group (−2.5 ± 5.9%, 0.2 ± 8.1%, 21.2 ± 79.3%, respectively) (P < 0.05). Of note, no significant differences in the cfPWV, carotid β‐stiffness, and circulating angiotensin II levels between the RT + HP (−2.4 ± 9.3%, 2.4 ± 10.3%, −5.7 ± 29.6%, respectively) and CON groups were observed. Furthermore, significant positive relationships between the percent changes in circulating angiotensin II levels, and cfPWV (r = 0.438, P < 0.01) and carotid β‐stiffness (r = 0.328, P < 0.01) were observed. Conclusions The combination of moderate to high‐intensity resistance training and regular intake of steamed chicken breast as a high‐protein food could increase muscle mass, strength, and quality and could cancel resistance training‐induced increases in arterial stiffness in elderly women.

Background Ageing is commonly associated with a decrease in muscle strength, which is largely linked to decreases in skeletal muscle mass (SMM). The rate of the age‐related decline in muscle strength is different from the rate of the age‐related decline in SMM. Current estimation methods for SMM, such as magnetic resonance imaging (MRI) and dual‐energy x‐ray absorptiometry (DXA), evaluate both intracellular and extracellular water volumes, potentially overestimating atrophied muscle fibres. Recently, segmental bioelectrical impedance spectroscopy (S‐BIS), which distinguishes intracellular water (ICW) associated with muscle cell mass (MCM), has been developed. However, this method has not been sufficiently compared with other SMM assessment methods, especially with respect to age‐related changes. This study was aimed at comparing the age‐related differences in SMM measured by S‐BIS, MRI and DXA over a wide range of ages and to identify the optimal method for evaluating age‐related muscle tissue changes. Methods This cross‐sectional study included 41 women and 43 men living in Japan (mean [SD] age: 53.51 [13.76] years; height: 162.96 [9.16] cm; BMI: 22.32 [2.94]). Three different methods were applied to estimate SMM: leg lean mass was measured via DXA; mid‐thigh muscle cross‐sectional area (CSA) was measured via MRI; and thigh total water, thigh ICW and the ratio of extracellular water to total water (ECW/TW) were measured via S‐BIS. To more effectively compare age‐related differences in each parameter, we normalised the relative values for each participant by using the mean scores for the 30–39‐year group for each parameter. Segmented regression analysis was performed to detect age breaking points for each parameter. Results Each SMM parameter obtained via the different methods markedly decreased with increasing age (p < 0.05). In contrast, the ECW/TW increased with increasing age (p < 0.05). The age breaking points for leg lean mass measured by DXA, mid‐thigh CSA measured by MRI and thigh ICW measured by S‐BIS were 57.7, 56.3 and 43.2 years, respectively (p < 0.05). Conclusions Compared with DXA or MRI, S‐BIS was found to be more sensitive for detecting age‐related SMM decrease at earlier stages. S‐BIS can distinguish between ICW and ECW, providing a more accurate estimation of MCM that is linked to muscle contractions. This study offers new insights that SMM begins to decrease in the 50s, while MCM does in the early 40s. These findings emphasise the need to address the age‐related decline in MCM starting in the early 40s to prevent a decrease in the quality of life of older individuals.