Tracking handgrip strength in Kendo athletes from university to middle and older adulthood.

OBJECTIVE: This study aimed to compare the current handgrip strength (HGS) of Kendo athletes with their HGS when they were in university (up to 50 years). METHODS: Eighty male graduates who were Kendo club members during their university days performed anthropometric and HGS measurements, and these HGS were compared with those measured during their university days (mean age of 19.5 years old). RESULTS: There was no evidence of a statistical difference in HGS between the current measurement and the measurement taken during university [-0.64 (-1.9, 0.67) kg, p = .336]. There was, however, evidence that the difference in HGS depended upon the current age of the individual (t = -6.43, p < .001). When probing the interaction, there were statistical differences between the ages of 24.6 and 38.2 years and between the ages of 47.4 and 69.9 years. Strength increased across time in the younger participants and decreased for those who were older. Between the ages of 38.9 and 46.1 years, there was no evidence of a statistical difference indicating a maintenance of strength. CONCLUSION: The HGS of Kendo club graduates, which they acquired during their formative years, continued to increase even after they graduated from university and entered their 30s. However, their HGS decreased from age 50, even though they practiced Kendo.

Blood biomarkers for estimating energy intake in Japanese male collegiate athletes: a pilot study.

BACKGROUND: Athletes should be informed of their required energy intake in preparation for sports competitions. However, the environment in which dietary surveys can be conducted to determine the required energy intake for sports competitions is limited, and such survey will require a substantial amount of time and effort from athletes and dietitians. If certain biomarkers for estimating the energy intake can be identified, they may compensate for the shortcomings of these dietary surveys. We aimed to identify the blood biomarkers to estimate the energy intake/basal metabolic rate ratio of male athletes. METHODS: Twenty-six male athletes from a university physical education department were included and underwent measurements of height, weight, and body composition, as well as blood sampling. The dietary assessment included a 3-day dietary recall and collection of meal photographs. The basal metabolic rate was estimated using the lean body mass, while the daily energy intake/basal metabolic rate ratio was used as an index to determine the energy intake. From the 36 selected blood biomarkers, we identified the independent biomarkers for inclusion in the multiple regression analysis by assessing for pairwise correlations and multicollinearity. A formula for estimating the energy intake/basal metabolic rate was then developed using the stepwise method. A p-value of < 0.05 was considered significant. RESULTS: Overall, 18 of the 36 blood biomarkers were selected, and multiple regression analysis revealed that triiodothyronine, white blood cell count, and triglyceride level were significant factors that can be used to estimate the energy intake/basal metabolic rate, accounting for 60.4% of the variance. No systematic errors were observed in the estimated values, calculated using the estimation formula and dietary assessment results. CONCLUSIONS: A combination of free triiodothyronine level, white blood cell count, and triglyceride level can be used for estimating the energy intake/basal metabolic rate of male athletes, thus compensating for the shortcomings of dietary surveys.

Correction: Ishihara et al. Association between Daily Physical Activity and Locomotive Syndrome in Community-Dwelling Japanese Older Adults: A Cross-Sectional Study. Int. J. Environ. Res. Public Health 2022, 19, 8164.

There was an error in the "d-value of the first paragraph in Section 3 (Results)" in the original publication (Page 5, Line 41) [...].

Longitudinal changes of grip strength and forearm muscle thickness in young children.

Background: Grip strength is a marker of future health conditions and is mainly generated by the extrinsic flexor muscles of the fingers. Therefore, whether or not there is a relationship between grip strength and forearm muscle size is vital in considering strategies for grip strength development during growth. Thus, this study aimed to examine the association between changes in grip strength and forearm muscle thickness in young children. Methods: Two hundred eighteen young children (104 boys and 114 girls) performed maximum voluntary grip strength and ultrasound-measured muscle thickness measurements in the right hand. Two muscle thicknesses were measured as the perpendicular distance between the adipose tissue-muscle interface and muscle-bone interface of the radius (MT-radius) and ulna (MT-ulna). All participants completed the first measurement and underwent a second measurement one year after the first one. Results: There were significant (P < 0.001) within-subject correlations between MT-ulna and grip strength [r = 0.50 (0.40, 0.60)] and MT-radius and grip strength [r = 0.59 (0.49, 0.67)]. There was no significant between-subject correlation between MT-ulna and grip strength [r = 0.07 (-0.05, 0.20)], but there was a statistically significant (P < 0.001) between-subject relationship between MT-radius and grip strength [r = 0.27 (0.14, 0.39)]. Conclusion: Although we cannot infer causation from the present study, our findings suggest that as muscle size increases within a child, so does muscle strength. Our between-subject analysis, however, suggests that those who observed the greatest change in muscle size did not necessarily get the strongest.

Defecation Habits in Preschoolers Are Associated with Physical Activity: A Cross-Sectional and Isotemporal Substitution Analysis.

There is a lack of research on the relationship between defecation habits (DF) and physical activity (PA) in preschoolers. This study aimed to clarify the relationship between sedentary behaviour (SB), PA time, and DF in preschoolers and to estimate the effect of DF replacement in an isotemporal substitution (IS) model. The participants included 166 children (aged 4-6 years) attending childcare facilities. PA was measured using an accelerometer to calculate the daily activity and wearing time for SB, light-intensity physical activity (LPA), and moderate-to-vigorous-intensity physical activity (MVPA). DF were classified based on defecation frequency and timing. A multinomial logistic regression analysis was used for the IS model. One-way analysis of variance detected significant differences in MVPA between the DF groups (F(2) = 3.12, p < 0.05). According to the analysis results of the IS model, replacing 5 min of SB with MVPA resulted in improved DF (odds ratio [OR], 0.89; 95% confidence interval [CI], 0.81-0.97). Conversely, replacing 5 min of MVPA with SB worsened DF (OR, 1.13; 95% CI, 1.03-1.23). The findings suggest that PA is associated with DF among preschoolers. It also indicates that replacing SB with MVPA could help improve DF in children.

Aquaporin 4 Expression Level Is Decreased in Skeletal Muscles with Aging.

Skeletal muscle is a tissue that contains abundant water. However, by aging a decrease in muscle water content is induced in skeletal muscles, which is one of major age-related alterations in skeletal muscles as common as muscle atrophy. Selective water channel aquaporin 4 (AQP4) is one of major water transport networks in the skeletal muscles. However, the effects of aging on water transport via AQP4 in skeletal muscles remain unclear. Thus, the current study investigated the change of the expression level of AQP4 in the aged skeletal muscles. Eight-week-old (the young group) and 2-year-old (the old group) female Fischer 344 rats were used in this study (n = 6/group). In skeletal muscles of each group, the expression levels of some target proteins were quantified by Western blot analysis. As a result, the relative muscle weight in the old group was significantly decreased, compared with that in the young group (p < 0.05). The decline in the muscle water content was accompanied by the decrease in expression of AQP4 in the aged skeletal muscles (p < 0.05, respectively). Moreover, the expression of transient receptor potential vanilloid 4, which synergistically regulates the osmolality together with AQP4, was significantly reduced in the aged skeletal muscles (p < 0.05). Therefore, the current study suggested that water transport abilities via AQP4 may decrease in the aged skeletal muscles, and thereby may be involved in age-related loss of muscle water content.

IL-4 Signaling Promotes Myoblast Differentiation and Fusion by Enhancing the Expression of MyoD, Myogenin, and Myomerger.

Myoblast fusion is essential for skeletal muscle development, growth, and regeneration. However, the molecular mechanisms underlying myoblast fusion and differentiation are not fully understood. Previously, we reported that interleukin-4 (IL-4) promotes myoblast fusion; therefore, we hypothesized that IL-4 signaling might regulate the expression of the molecules involved in myoblast fusion. In this study, we showed that in addition to fusion, IL-4 promoted the differentiation of C2C12 myoblast cells by inducing myoblast determination protein 1 (MyoD) and myogenin, both of which regulate the expression of myomerger and myomaker, the membrane proteins essential for myoblast fusion. Unexpectedly, IL-4 treatment increased the expression of myomerger, but not myomaker, in C2C12 cells. Knockdown of IL-4 receptor alpha (IL-4Rα) in C2C12 cells by small interfering RNA impaired myoblast fusion and differentiation. We also demonstrated a reduction in the expression of MyoD, myogenin, and myomerger by knockdown of IL-4Rα in C2C12 cells, while the expression level of myomaker remained unchanged. Finally, cell mixing assays and the restoration of myomerger expression partially rescued the impaired fusion in the IL-4Rα-knockdown C2C12 cells. Collectively, these results suggest that the IL-4/IL-4Rα axis promotes myoblast fusion and differentiation via the induction of myogenic regulatory factors, MyoD and myogenin, and myomerger.

Athletes in sporting events with upper-body gripping movements have greater handgrip strength than those in sporting events that prioritize the lower body.

OBJECTIVE: Evidence suggests that acquiring a high level of handgrip strength early in life and maintaining that strength throughout life may be important for health. In addition, it is thought that sports activities performed during the developmental period are effective in improving handgrip strength, but it is unknown what types of sports are more effective. As a first step, we conducted a cross-sectional study to compare handgrip strength across different sports (upper-body gripping sports vs. lower body) in early adulthood. METHODS: We used the Juntendo Fitness Plus Study data from 1973 to 2018 and selected two types of sporting events with matching physiques (soccer, baseball, and kendo) but different degrees of gripping. Data on 7344 male first-year sports university students included 1127 soccer, 297 Kendo, and 698 baseball players. RESULTS: Those in the lower body-only (soccer) sports had -3.78 (95% CI: -4.27, -3.29) kg lower handgrip strength than those in the lower + upper (kendo and baseball). Comparing each individual sport found that each sport was different from each other with Kendo > Baseball > Soccer (between each sport, p < .001). In addition, the difference between sports has become greater across time. CONCLUSIONS: In early adulthood, handgrip strength is greatest in those participating in sports with upper-body movements compared to those participating in sports that mainly involved lower-body movements. The three sports we selected are natural activities that do not directly train handgrip strength. Therefore, sport may be one potential method to improve low handgrip strength in children/adolescents during the developmental period.

Handgrip Strength and Healthspan: Impact of Sports During the Developmental Period on Handgrip Strength (Juntendo Fitness Plus Study).

Handgrip strength as a biomarker is being studied as a factor in predicting disease onset. However, the effect of improving handgrip strength through physical exercises, such as sports during the developmental period, on disease prevention has yet to be fully elucidated. The Juntendo Fitness Plus (J-Fit Plus) Study is a unique database of anthropometric and physical fitness measurements with over 50 years of accumulated data. It has the potential to explore the effects of sports on the association between handgrip strength and morbidity/mortality. We first outline previous studies on the impact of physical exercise interventions on handgrip strength, separated into adulthood and developmental period. We then introduced a unique effort to investigate the effects of sports using the J-Fit Plus Study database and describe the challenges of finally elucidating the impact of exercise on the association between handgrip strength and health status.

Vitamin C Is Essential for the Maintenance of Skeletal Muscle Functions.

Vitamin C (L-ascorbic acid, VC) is a water-soluble antioxidant essential for collagen polymerization. Previously, we reported that long-term VC deficiency causes muscle atrophy and deterioration in physical ability using female senescence marker protein-30 (SMP30)-deficient mice with a lack of VC synthesis, which is similar to that observed in humans. To determine whether these findings also hold true for male SMP30-deficient mice, two-month-old male SMP30-deficient mice were divided into two groups: the VC-treated group (VC(+)) was administered 1.5 g/L VC, and the VC-untreated group (VC(-)) was supplied water without VC. The VC level at four weeks in the gastrocnemius muscles from the VC(+) and VC(-) groups was 205.7 ± 8.5 nmol/g tissue and 13.1 ± 0.6 nmol/g tissue, respectively. Thus, four weeks was enough to reduce the VC level in the skeletal muscle in the VC-untreated group. On the other hand, muscle weights of the gastrocnemius, soleus, plantaris, tibialis anterior, and extensor digitorum longus in the VC(-) group were significantly reduced by VC deficiency after twelve weeks. The physical endurance of the VC(-) group at eight weeks was markedly lower than that of the VC(+) group. The grasping strength and activity in the cage in the nocturnal phases of the VC(-) group were markedly lower at twelve and sixteen weeks than those of the VC(+) group. Interestingly, muscle atrophy and declined physical ability were completely restored with VC supplementation for twelve weeks after VC deficiency. Thus, VC is essential for maintaining skeletal muscle function in both male and female SMP30-deficient mice with a lack of VC synthesis.

Influence of oestrogen on satellite cells and myonuclear domain size in skeletal muscles following resistance exercise.

BACKGROUND: Oestrogen deficiency reduces skeletal muscle mass and force generation in postmenopausal women. Muscle mass is maintained by satellite cells, which are regulated by oestrogen. Although oestrogen therapy enhances muscle hypertrophy induced by resistance training in postmenopausal women, the molecular mechanism is unclear. METHODS: Adult female rats (10 weeks old) were divided into six groups: sham sedentary (Sham-Sed), sham climbing training (Sham-CT), ovariectomy sedentary (OVX-Sed), ovariectomy climbing training (OVX-CT), ovariectomy plus oestrogen treatment sedentary (OVX+E-Sed), and ovariectomy plus oestrogen treatment climbing training (OVX+E-CT). At 8 weeks after ovariectomy, rats in the training group were trained (one session every 3 days for 8 weeks) to climb a ladder while bearing a load. Oestrogen treatment involved subcutaneous insertion of a 17ß-oestradiol pellet. After 8 weeks, the flexor hallucis longus muscle was collected and analysed. RESULTS: Following climbing training, the flexor hallucis longus muscle mass and muscle-to-body weight ratios were dramatically increased by training (main effect of training, P < 0.01); the OVX+E-CT group showed the highest values (main effect of group, P < 0.01). The cross-sectional area of all muscle fibre types was increased by training (main effect of training, P < 0.01). Particularly, the cross-sectional area of MHC IIa in the OVX+E-CT group was significantly larger than that in the Sham-CT and OVX-CT groups. Satellite cell numbers were increased in all training groups (main effect of training, P < 0.05), and the myonuclear number was increased by training (main effect of training, P < 0.01), but there was no main group effect. The myonuclear domain size of all muscle fibre types and MHC IIa was increased in all training groups (main effect of training, P < 0.01) and showed a main group effect (P < 0.01). The myonuclear domain sizes of all muscle fibre types and MHC IIa in the OVX+E-CT group were significantly larger than those in the Sham-CT and OVX-CT groups. The total RNA contents revealed main effects of training and the group (P < 0.01); the OVX+E-CT group showed the highest contents (main effect of group, P < 0.01). The mRNA and protein levels of rpS6 were increased in the OVX+E-Sed and CT groups (main effects of group, P < 0.05). Particularly, the 28S ribosomal RNA content in OVX+E-Sed group was significantly higher than that in the OVX-Sed group. CONCLUSIONS: Oestrogen enhanced the resistance training-induced increase in myonuclear domain size but did not affect satellite cells and ribosome biogenesis.

Loquat Leaf Extract Enhances Muscle Contraction-Induced Activation of Protein Synthesis Signaling in Rat Skeletal Muscle.

Loquat (Eriobotrya japonica (Thunb.) Lindl.) leaves are traditionally used to improve muscle weakness, but their effects on muscle protein synthesis require further research. Therefore, we aimed to investigate whether loquat leaf extract (LLE) enhances muscle contraction-induced activation of muscle protein synthesis signaling. Male Wistar rats (12 weeks old, n = 6/group) were categorized into water treatment (CON) and LLE treatment (LLE) groups. The rats were administered distilled water or LLE (1.5 g/kg/day) once a day by oral gavage for 7 days. On day 7, at 3 h post-LLE administration, the gastrocnemius muscle in the right leg of each rat was stimulated by electrical muscle stimulation (EMS) (100 Hz, 30 V) through five sets of 10 isometric contractions (7 s contraction, 3 s rest) with 3 min interset intervals. The rats were then sacrificed, and the gastrocnemius muscles of both legs were excised at 3 h post-EMS. The phosphorylation levels of mammalian target of rapamycin complex 1 (mTORC1) signaling pathway molecules (Akt, mTOR, and p70S6K) were determined by Western blotting. Regarding the muscle contraction-induced protein synthesis signaling pathway, Akt phosphorylation at Ser473 was not significantly different between the CON and LLE groups. mTOR phosphorylation at Ser2448 was increased by EMS but did not show a significant difference between the CON and LLE groups. p70S6K phosphorylation at Thr389 was significantly increased in response to EMS, whereas the LLE group showed significantly higher p70S6K phosphorylation at Thr389 than that in the CON group. This suggests that LLE enhances muscle contraction-induced activation of p70S6K phosphorylation in rat skeletal muscles.

Association between Daily Physical Activity and Locomotive Syndrome in Community-Dwelling Japanese Older Adults: A Cross-Sectional Study.

This study aimed to evaluate the association between locomotive syndrome (LS) and daily physical activity (PA) in community-dwelling older adults. This cross-sectional study included 80 healthy Japanese older adults (40 men and 40 women; age: 60-79 years). Habitual daily PA was evaluated using a triaxial wrist accelerometer. Participants were divided into two groups based on the results of the two-step test, stand-up test, and 25-question geriatric locomotive function scale. Binomial logistic regression analysis was conducted to examine the statistical relationships between daily PA and category of LS, adjusting for age from adjusted odds ratio (adjusted OR) with the 95 percent confidence intervals (95%CI) and bootstrap 95%CI. The mean step count and time spent on moderate to vigorous physical activity (MVPA) were significantly higher among non-LS participants than among LS participants in women, but not in men. Logistic regression analyses indicated that spending longer than 28 min/day on MVPA was significantly associated with a lower likelihood of LS relative to short time category under 28 min/day in women (adjusted OR = 0.12, 95%CI = 0.02-0.59, bootstrap 95%CI = 0.01-0.43), but not in men. This study suggests that in community-dwelling older women, those with higher MVPA had lower odds of LS, and daily MVPA was associated with LS, but not in men. Therefore, the associations between LS and daily physical activity were partly dependent on sex differences.

Sports activities at a young age decrease hypertension risk-The J-Fit+ study.

This study aimed to assess (1) blood pressure between young, current athletes, and non-athletes early in life; (2) hypertension prevalence between former athletes and the general population later in life; and (3) understand the mechanisms between exercise training and hypertension risks in the form of DNA methylation. Study 1: A total of 354 young male participants, including current athletes, underwent blood pressure assessment. Study 2: The prevalence of hypertension in 1269 male former athletes was compared with that in the Japanese general population. Current and former athletes were divided into three groups: endurance-, mixed-, and sprint/power-group. Study 3: We analyzed the effect of aerobic- or resistance-training on DNA methylation patterns using publicly available datasets to explore the possible underlying mechanisms. In young, current athletes, the mixed- and sprint/power-group exhibited higher systolic blood pressure, and all groups exhibited higher pulse pressure than non-athletes. In contrast, the prevalence of hypertension in former athletes was significantly lower in all groups than in the general population. Compared to endurance-group (reference), adjusted-hazard ratios for the incidence of hypertension among mixed- and sprint/power-group were 1.24 (0.87-1.84) and 1.50 (1.04-2.23), respectively. Moreover, aerobic- and resistance-training commonly modified over 3000 DNA methylation sites in skeletal muscle, and these were suggested to be associated with cardiovascular function-related pathways. These findings suggest that the high blood pressure induced by exercise training at a young age does not influence the development of future hypertension. Furthermore, previous exercise training experiences at a young age could decrease the risk of future hypertension.

Mitochondrial fusion- and fission-related protein expression in the regulation of skeletal muscle mass.

Mitochondria in the skeletal muscle are essential for maintaining metabolic plasticity and function. Mitochondrial quality control encompasses the dynamics of the biogenesis and remodeling of mitochondria, characterized by the constant fission and fusion of mitochondria in response to metabolic stressors. However, the roles of mitochondrial fission or fusion in muscle hypertrophy and atrophy remain unclear. The aim of this study was to determine whether mitochondrial fusion and fission events are influenced by muscle hypertrophy or atrophy stimulation. Twenty-six male F344 rats were randomly assigned to a control group or were subjected to up to 14 days of either plantaris overload (via tenotomy of the gastrocnemius and soleus muscles; hypertrophy group) or hindlimb cast immobilization (atrophy group). After 14 days of treatment, plantaris muscle samples were collected to determine the expression levels of mitochondrial fusion- and fission-related proteins. Muscle weight and total muscle protein content increased following plantaris overload in the hypertrophy group, but decreased following immobilization for 14 days in the atrophy group. In the hypertrophied muscle, the level of activated dynamin-related protein 1 (Drp1), phosphorylated at Ser616, significantly increased by 25.8% (p = 0.014). Moreover, the protein expression level of mitochondrial fission factor significantly decreased by 36.5% in the hypertrophy group compared with that of the control group (p = 0.017). In contrast, total Drp1 level significantly decreased in the atrophied plantaris muscle (p = 0.011). Our data suggest that mitochondrial fission events may be influenced by both muscle hypertrophy and atrophy stimulation, and that mitochondrial fission- related protein Drp1 plays an important role in the regulation of skeletal muscle in response to mechanical stimulation.

Circadian rhythms modulate the effect of eccentric exercise on rat soleus muscles.

We investigated whether time-of-day dependent changes in the rat soleus (SOL) muscle size, after eccentric exercises, operate via the mechanistic target of rapamycin (mTOR) signaling pathway. For our first experiment, we assigned 9-week-old male Wistar rats randomly into four groups: light phase (zeitgeber time; ZT6) non-trained control, dark phase (ZT18) non-trained control, light phase-trained, and dark phase-trained. Trained animals performed 90 min of downhill running once every 3 d for 8 weeks. The second experiment involved dividing 9-week-old male Wistar rats to control and exercise groups. The latter were subjected to 15 min of downhill running at ZT6 and ZT18. The absolute (+12.8%) and relative (+9.4%) SOL muscle weights were higher in the light phase-trained group. p70S6K phosphorylation ratio was 42.6% higher in the SOL muscle of rats that had exercised only in light (non-trained ZT6). Collectively, the degree of muscle hypertrophy in SOL is time-of-day dependent, perhaps via the mTOR/p70S6K signaling.

The MOTS-c K14Q polymorphism in the mtDNA is associated with muscle fiber composition and muscular performance.

Human skeletal muscle fiber is heterogenous due to its diversity of slow- and fast-twitch fibers. In human, slow-twitched fiber gene expression is correlated to MOTS-c, a mitochondria-derived peptide that has been characterized as an exercise mimetic. Within the MOTS-c open reading frame, there is an East Asian-specific m.1382A>C polymorphism (rs111033358) that changes the 14th amino acid of MOTS-c (i.e., K14Q), a variant of MOTS-c that has less biological activity. Here, we examined the influence of the m.1382A>C polymorphism causing MOTS-c K14Q on skeletal muscle fiber composition and physical performance. The myosin heavy chain (MHC) isoforms (MHC-I, MHC-IIa, and MHC-IIx) as an indicator of muscle fiber composition were assessed in 211 Japanese healthy individuals (102 men and 109 women). Muscular strength was measured in 86 physically active young Japanese men by using an isokinetic dynamometer. The allele frequency of the m.1382A>C polymorphism was assessed in 721 Japanese athletes and 873 ethnicity-matched controls. The m.1382A>C polymorphism genotype was analyzed by TaqMan SNP Genotyping Assay. Individuals with the C allele of the m.1382A>C exhibited a higher proportion of MHC-IIx, an index of fast-twitched fiber, than the A allele carriers. Men with the C allele of m.1382A>C exhibited significantly higher peak torques of leg flexion and extension. Furthermore, the C allele frequency was higher in the order of sprint/power athletes (6.5%), controls (5.1%), and endurance athletes (2.9%). Additionally, young male mice were injected with the MOTS-c neutralizing antibody once a week for four weeks to mimic the C allele of the m.1382A>C and assessed for protein expression levels of MHC-fast and MHC-slow. Mice injected with MOTS-c neutralizing antibody showed a higher expression of MHC-fast than the control mice. These results suggest that the C allele of the East Asian-specific m.1382A>C polymorphism leads to the MOTS-c K14Q contributes to the sprint/power performance through regulating skeletal muscle fiber composition.

Effect of Gear Ratio and Cadence on Gross Efficiency and Pedal Force Effectiveness during Multistage Graded Cycling Test Using a Road Racing Bicycle.

Gross efficiency (GE) and the index of pedal force effectiveness (IFE) are important factors that enhance cyclists' performance; however, the effects of changing pedal force (gear ratio) and cadence on these indices while riding on a road racing bicycle are poorly investigated. This study aimed to examine the effect of changing gear ratio or cadence on GE and IFE using a road racing bicycle. Nine male cyclists completed graded submaximal cycling tests (five stages of 4 min submaximal cycling sessions with 1 min passive rest intervals). The work rate of each stage was determined using two principles: changing gear ratio at a fixed cadence and changing cadence at a fixed gear ratio. We determined GE and IFE using respiratory variables and pedal reaction forces, respectively. Increasing the gear ratio improved GE, and was associated with the IFE. Although increasing the cadence slightly improved GE from the initial level, the increased values then mostly maintained. IFE was almost stable even when cadence increased. Moreover, no significant correlation was observed between the changes in GE and IFE accompanied by increasing cadence. Our data indicate that an increasing gear ratio, but not cadence, may affect GE and IFE while riding on a road racing bicycle.

Design and Evaluation of an Online Squat Fitness System: Lessons Learned During the Early COVID-19 Pandemic in Japan.

COVID-19 has changed our lives and limited our ability to have adequate physical activity (PA). It is necessary to replace outdoor PA with home-based fitness. However, people lack access, skills, and even motivation for home-based fitness. To address these issues, we designed a free access self-monitoring and coaching and music-based interactive online squat fitness system. Body weight squat was utilized for fitness exercise and evaluated based on three indices: knee width, hip depth, and rhythm. An online survey on changes in exercise due to the COVID-19 pandemic and exercise habits was conducted to investigate the effect of the COVID-19 pandemic on PA. We collected data from 557 respondents 5 months after the system first released and analyzed 200 visitors' performance on squat exercise and the other relevant parameters. Visitors were divided into three groups according to their age: younger, middle, and older groups. Results showed that the younger group had better squat performance than the middle and older groups in terms of hip depth and rhythm. We highlighted the lessons learned about the system design, fitness performance evaluation, and social aspects, for future study of the design and development of similar home-based fitness systems. We provided first-hand results on the relation between the COVID-19 pandemic and physical exercise among different age groups in Japan, which was valuable for policy making in the post-COVID-19 era.

Serum albumin levels as a predictive biomarker for low-load resistance training programs' effects on muscle thickness in the community-dwelling elderly Japanese population: interventional study result.

BACKGROUND: Resistance training has been recommended as an effective measure against age-related loss of muscle mass and muscle strength, called sarcopenia, even in older adults. However, despite subjecting each participant to the same training program, the training effect solely depended on the individual. This study aimed to evaluate whether certain blood parameters influenced the effect of a low-load resistance training program on muscle thickness in the community-dwelling elderly population. METHODS: Sixty-nine community-dwelling Japanese (49 women and 20 men) subjects aged 69.4 ± 6.5 years were included. Low-load resistance training was performed twice a week for 12 weeks. Muscle thickness at the anterior aspects of the thigh (AT) was measured using a B-mode ultrasound device, and 22 blood parameter levels were assessed before and after the program. We checked the first quartile value of each parameter to establish cutoff values, and participants were divided into low or normal groups for each parameter. RESULTS: A low-load resistance training program significantly increased muscle thickness at the AT. The interaction between time and groups was examined at low (< 4.1 g/dL) versus normal (≥ 4.1 g/dL) serum albumin (Alb) levels. Although there was no difference in muscle thickness at the AT before the training intervention, the hypertrophic effects were higher in the normal serum Alb level group than in the low serum Alb level group. The binomial logistic regression analysis showed that participants in the low serum Alb group had an odds ratio of 7.08 for decreased muscle thickness at the AT. The effect of a low-load resistance training program on lower limb muscle thickness appears to be limited in participants with low serum Alb levels before training interventions. CONCLUSIONS: Serum Alb level may act as a biomarker to predict the effects of low-load resistance training programs on muscle hypertrophy in elderly individuals. TRIAL REGISTRATION: This study was retrospectively registered in UMIN-Clinical Trial Registry (CTR), ID: UMIN000042759 (date of registration, 14 Dec 2020).