Japan's cancer survivorship guidelines for exercise and physical activity.

OBJECTIVE: This research aimed to establish the inaugural evidence-based cancer survivorship guidelines for Japan, with a particular focus on exercise and physical activity, in order to enhance health outcomes for cancer survivors. METHODS: A panel of experts, including oncologists, physicians, exercise scientists, epidemiologists and patient advocates, utilized a modified Delphi process and systematic reviews to establish consensus on exercise recommendations for cancer survivors. The panel focused on setting the objectives of the Clinical Practice Guidelines and addressing crucial clinical issues in Japan. Recommendations were formulated based on the strength and certainty of evidence, the benefit-harm balance and patient values and preferences. RESULTS: The panel formulated exercise recommendations for cancer survivors of two age groups: 18-64 years and ≥65 years. The recommendations for both age groups are consistent, emphasizing the importance of regular exercise and physical activity tailored to individual capabilities and health conditions. The guidelines underline the benefits of exercise in improving the overall health and quality of life of cancer survivors. This consensus on exercise recommendations marks a significant step in the development of comprehensive cancer survivorship guidelines in Japan, with potential implications for improving clinical outcomes and advancing research in cancer survivorship. CONCLUSIONS: These guidelines will serve as a critical resource for cancer survivors, highlighting exercise as a key component of survivorship care, and for clinicians, in recommending appropriate physical activities to improve survivor health and well-being.

Klotho regulates the myogenic response of muscle to mechanical loading and exercise.

NEW FINDINGS: What is the central question of this study? Does the hormone Klotho affect the myogenic response of muscle cells to mechanical loading or exercise? What is the main finding and its importance? Klotho prevents direct, mechanical activation of genes that regulate muscle differentiation, including genes that encode the myogenic regulatory factor myogenin and proteins in the canonical Wnt signalling pathway. Similarly, elevated levels of klotho expression in vivo prevent the exercise-induced increase in myogenin-expressing cells and reduce exercise-induced activation of the Wnt pathway. These findings demonstrate a new mechanism through which the responses of muscle to the mechanical environment are regulated. ABSTRACT: Muscle growth is influenced by changes in the mechanical environment that affect the expression of genes that regulate myogenesis. We tested whether the hormone Klotho could influence the response of muscle to mechanical loading. Applying mechanical loads to myoblasts in vitro increased RNA encoding transcription factors that are expressed in activated myoblasts (Myod) and in myogenic cells that have initiated terminal differentiation (Myog). However, application of Klotho to myoblasts prevented the loading-induced activation of Myog without affecting loading-induced activation of Myod. This indicates that elevated Klotho inhibits mechanically-induced differentiation of myogenic cells. Elevated Klotho also reduced the transcription of genes encoding proteins involved in the canonical Wnt pathway or their target genes (Wnt9a, Wnt10a, Ccnd1). Because the canonical Wnt pathway promotes differentiation of myogenic cells, these findings indicate that Klotho inhibits the differentiation of myogenic cells experiencing mechanical loading. We then tested whether these effects of Klotho occurred in muscles of mice experiencing high-intensity interval training (HIIT) by comparing wild-type mice and klotho transgenic mice. The expression of a klotho transgene combined with HIIT synergized to tremendously elevate numbers of Pax7+ satellite cells and activated MyoD+ cells. However, transgene expression prevented the increase in myogenin+ cells caused by HIIT in wild-type mice. Furthermore, transgene expression diminished the HIIT-induced activation of the canonical Wnt pathway in Pax7+ satellite cells. Collectively, these findings show that Klotho inhibits loading- or exercise-induced activation of muscle differentiation and indicate a new mechanism through which the responses of muscle to the mechanical environment are regulated.

Comorbid insomnia among breast cancer survivors and its prediction using machine learning: a nationwide study in Japan.

OBJECTIVE: Insomnia is an increasingly recognized major symptom of breast cancer which can seriously disrupt the quality of life during and many years after treatment. Sleep problems have also been linked with survival in women with breast cancer. The aims of this study were to estimate the prevalence of insomnia in breast cancers survivors, clarify the clinical characteristics of their sleep difficulties and use machine learning techniques to explore clinical insights. METHODS: Our analysis of data, obtained in a nationwide questionnaire survey of breast cancer survivors in Japan, revealed a prevalence of suspected insomnia of 37.5%. With the clinical data obtained, we then used machine learning algorithms to develop a classifier that predicts comorbid insomnia. The performance of the prediction model was evaluated using 8-fold cross-validation. RESULTS: When using optimal hyperparameters, the L2 penalized logistic regression model and the XGBoost model provided predictive accuracy of 71.5 and 70.6% for the presence of suspected insomnia, with areas under the curve of 0.76 and 0.75, respectively. Population segments with high risk of insomnia were also extracted using the RuleFit algorithm. We found that cancer-related fatigue is a predictor of insomnia in breast cancer survivors. CONCLUSIONS: The high prevalence of sleep problems and its link with mortality warrants routine screening. Our novel predictive model using a machine learning approach offers clinically important insights for the early detection of comorbid insomnia and intervention in breast cancer survivors.

Accuracy of exercise-based tests for estimating cardiorespiratory fitness and muscle strength in early-stage breast cancer survivors in Japan.

PURPOSE: We aimed to examine whether cardiorespiratory fitness and leg strength can be estimated based on their relationship with physical performance tests in Japanese breast cancer survivors. METHODS: Participants were 50 sedentary women aged 20 to 59 years who have received breast surgery in the past 2 to 13 months after diagnosis of invasive breast cancer (stage I-IIa). Cardiorespiratory fitness and leg strength were measured by peak oxygen consumption (VO2peak), and one-repetition maximum for leg press (leg press 1RM). Physical performance tests were performed 6-min walk test, chair stand test, and grip strength. Using multiple regression analysis, we developed prediction equations for VO2peak and leg strength based on their associations with the physical performance tests. The validity of the estimation equations was assessed using Bland-Altman plots. RESULTS: Mean age, VO2peak, and leg press 1RM were 48 ± 6 years, 25.0 ± 3.6 mL/kg/min, and 95 ± 32 kg, respectively. Multiple regression analysis yielded 6-min walk test distance, age, height, and body weight as predictors of VO2peak. Measured VO2peak and predicted VO2peak showed a moderate positive correlation (r = 0.463, p < 0.001). Chair stand test, grip strength, age, height, and body weight were selected as predictors of leg press 1RM. There was a strong positive correlation between predicted and measured leg press 1RM (r = 0.754, p < 0.001). CONCLUSION: The results suggest that leg strength can be predicted using physical performance tests. However, further examination may be needed to determine whether cardiorespiratory fitness can be predicted based on 6-min walk test.

Oncology care providers' awareness and practice related to physical activity promotion for breast cancer survivors and barriers and facilitators to such promotion: a nationwide cross-sectional web-based survey.

PURPOSE: A known barrier to getting breast cancer survivors (BCSs) to engage in habitual exercise is a lack of information on recommended physical activity levels provided to them by oncology care providers (OCPs). However, the actual situation in Japan remains unclear. This study sought to clarify OCPs' awareness and practice related to Japan's physical activity recommendation for BCSs and to ascertain barriers to routine information provision. METHODS: We conducted a web-based survey involving members of the Japanese Breast Cancer Society (JBCS) and the Japanese Association of Cancer Rehabilitation between Dec. 2018 and Feb. 2019. RESULTS: Of 10,830 members, 1,029 (9.5%) responded. Only 19.1% were aware of the details of the JBCS physical activity recommendation, and only 21.2% routinely provided physical activity information to BCSs. Factors related to being aware of the recommendation details were 1) availability of the guidelines, 2) experience reading relevant parts of the guidelines, and 3) involvement in multidisciplinary team case meetings. Barriers to routine information provision were 1) absence of perceived work responsibility, 2) underestimation of survivors' needs, 3) lack of resources, 4) lack of self-efficacy about the recommendation, and 5) poor knowledge of the recommendation. CONCLUSIONS: Only one fifth of the OCPs routinely provided physical activity information. Barriers to provision were poor awareness, self-efficacy, and attitudes and unavailable resources. The physical activity recommendation needs to be disseminated to all OCPs and an information delivery system needs to be established for BCSs to receive appropriate information and support to promote their engagement in habitual physical activity.

High-intensity interval training in breast cancer survivors: a systematic review.

BACKGROUND: To review the settings and outcomes of high-intensity interval training (HIIT) interventions for breast cancer survivors, and to explore the feasibility of prescribing exercise for breast cancer survivors. METHODS: A systematic search of electronic databases was conducted for studies published up to May 31, 2020. Eligibility criteria included randomized controlled trials of HIIT intervention in breast cancer survivors. Studies were grouped by whether the intervention was conducted during or after breast cancer treatment, and intervention methods and outcomes were reviewed within each group. RESULTS: Twenty-six studies were identified, and 13 satisfied the inclusion criteria. Intervention was conducted during treatment in 8 studies, and after treatment in 5. Intervention duration ranged from 3 to 16 weeks, with 2 or 3 sessions per week, for a total of 9 to 36 sessions. All interventions were supervised; 12 were lab-based, and 1 was community-based. One of most promising outcomes was improvement of cardiorespiratory fitness by HIIT. CONCLUSION: This review found that all studies on HIIT for breast cancer survivors investigated lab-based, supervised interventions, but not home-based or unsupervised. HIIT is a time-efficient method for increasing cardiovascular function in breast cancer survivors, but further research is necessary to determine its effects on other outcomes.

Low Dose of ß-Hydroxy-ß-Methylbutyrate (HMB) Alleviates Muscle Strength Loss and Limited Joint Flexibility following Eccentric Contractions.

Objective: The optimal dose of ß-hydroxy-ß-methylbutyrate (HMB) required for decreasing muscle damage remains unknown. Therefore, this study investigated the supplemental effect of low-dose HMB on muscle damage following eccentric contractions (ECCs) of human elbow flexors.Methods: Twenty untrained men (aged 20-26; height, 169.4 ± 5.7 cm; weight, 68.2 ± 11.3 kg; body mass index, 23.7 ± 3.3) completed the double-blind, placebo-controlled, parallel design study. The subjects were randomly assigned to the ingestion of HMB supplement (HMB, n = 10) or placebo group (PL, n = 10). After the subjects of 1.5 g HMB or placebo pills per day for 2 weeks, they performed six sets of 10 ECCs at 100% maximal voluntary contraction (MVC) using dumbbell. Changes in MVC torque, range of motion (ROM), upper arm circumference, muscle soreness, and muscle stiffness were assessed before, immediately after, 1, 2, 3, 5 days after exercise.Results: MVC torque was significantly higher in the HMB group than in the PL group immediately after (HMB, -56.8%; PL, -67.1%) as well as 3 (HMB: -25.5%, PL: -48.7%) and 5 (HMB: -22.5%, PL: -44.0%) days after performing ECCs (p < 0.05). Additionally, ROM was significantly higher in the HMB group than in the PL group immediately after (HMB, -29.8%; PL, -50.5%) and 5 (HMB: -26.1%, PL: -43.3%) days after performing ECCs (p < 0.05). No between-group differences were observed in other muscle damage markers.Conclusion: The low-dose HMB supplementation demonstrated a moderate overall impact and played a beneficial role in muscle dysfunction and joint flexibility following ECCs.

Eccentric exercise causes delayed sensory nerve conduction velocity but no repeated bout effect in the flexor pollicis brevis muscles.

PURPOSE: This study was aimed at investigating the effect of eccentric contractions (ECCs) of flexor pollicis brevis muscles (FPBMs) on motor and sensory nerve functions as well as the ipsilateral repeated bout effect (IL-RBE) and contralateral (CL)-RBE of motor and sensory nerve conduction velocities following ECCs. METHODS: Thirty-two young healthy men (age: 19.6 ± 0.2 years, height: 173.2 ± 1.2 cm, body mass: 69.7 ± 1.9 kg) performed two bouts of ECCs. During the first ECCs bout (ECCs-1), all participants performed 100 ECCs with 1 hand; for the second bout, 3 groups (2 weeks [W]: n = 11, 4W: n = 10, 8W: n = 11) performed ECCs with both hands 2, 4, or 8 weeks after ECCs-1. The maximal voluntary isometric contraction (MVC), range of motion (ROM), visual analog scale for pain (VAS), motor and sensory nerve conduction velocities were measured before, immediately after, and 1, 2, 3, and 5 days after ECCs. RESULTS: ECCs-1 decreased the MVC, limited the ROM, developed VAS, and decreased the motor and sensory nerve conduction velocities compared to non-exercise hand (p < 0.05). The repeated bout effect was observed in the ROM for IL-RBE in 2W and 4W, VAS for IL-RBE in 2 W, and ROM and VAS for CL-RBE in 2W (p < 0.05). However, RBEs of MVC and motor and sensory nerve conduction velocities were not observed, and no differences were confirmed depending on the interval. CONCLUSION: In the present study, ECCs of the FPBM caused a sensory nerve dysfunction, while IL- or CL-RBE was not observed.

Eccentric contraction-induced muscle damage in human flexor pollicis brevis is accompanied by impairment of motor nerve.

BACKGROUND: Eccentric contractions (ECCs) cause muscle damage. In addition, we showed that ECCs induce nerve dysfunction and damage with rats and human. PURPOSE: We aimed to evaluate motor nerve conduction velocity (MCV) for flexor pollicis brevis muscle (FPBM) after ECCs. METHODS: Twelve men (years, 19.8 ± 1.7 years; height, 172.4 ± 7.0 cm; weight, 64.0 ± 8.6 kg) performed maximal 100 ECCs on their FPBM of non-dominant hands with torque dynamometer. The dominant hands were control (CON). Maximal voluntary contraction (MVC), range of motion (ROM), DOMS, and MCV were assessed before, immediately post, and 1, 2, and 5 days after ECCs. MCV was calculated as the distance by stimulation divided by the latencies of the waveforms generated. Values were statistically analyzed by two-way ANOVA, and the significance level was set at P < .05. RESULTS: Decreases in MVC immediately (-32.9%) to 5 days after ECCs were significantly greater (P < .05) than for the CON group. ROM showed a significant decrease immediately (-21.6%) after ECCs compared with before ECCs and CON group (P < .05). DOMS after ECCs increased at 1 and 2 days (5.0 cm) after ECCs compared with before ECCs and CON (P < .05). Also, MCV after ECCs delayed significantly from immediately (-36.4%), 1, 2, and 5 days after ECCs compared with CON (P < .05), while no significant change in M-wave amplitude was observed over time for both ECCs and CON. CONCLUSION: The present study showed that ECCs of the FPBM cause a significant delay in MCV of median nerve.

Data Validation and Verification Using Blockchain in a Clinical Trial for Breast Cancer: Regulatory Sandbox.

BACKGROUND: The integrity of data in a clinical trial is essential, but the current data management process is too complex and highly labor-intensive. As a result, clinical trials are prone to consuming a lot of budget and time, and there is a risk for human-induced error and data falsification. Blockchain technology has the potential to address some of these challenges. OBJECTIVE: The aim of the study was to validate a system that enables the security of medical data in a clinical trial using blockchain technology. METHODS: We have developed a blockchain-based data management system for clinical trials and tested the system through a clinical trial for breast cancer. The project was conducted to demonstrate clinical data management using blockchain technology under the regulatory sandbox enabled by the Japanese Cabinet Office. RESULTS: We verified and validated the data in the clinical trial using the validation protocol and tested its resilience to data tampering. The robustness of the system was also proven by survival with zero downtime for clinical data registration during a Amazon Web Services disruption event in the Tokyo region on August 23, 2019. CONCLUSIONS: We show that our system can improve clinical trial data management, enhance trust in the clinical research process, and ease regulator burden. The system will contribute to the sustainability of health care services through the optimization of cost for clinical trials.

Eicosapentaenoic Acid-Rich Fish Oil Supplementation Inhibits the Decrease in Concentric Work Output and Muscle Swelling of the Elbow Flexors.

OBJECTIVE: The aim of this study was to test the hypothesis that 8-week eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) supplementation improves peripheral muscle performance by concentric contractions (CONs) of elbow flexors in humans. METHODS: Sixteen healthy men were randomly administered with EPA and DHA supplement (EPA, n = 8) or placebo (PL, n = 8) by a double-blind method. The EPA group was administered EPA-rich fish oil, containing 600 mg EPA and 260 mg DHA per day for 8 weeks. The subjects performed 5 sets of 6 maximal CONs of elbow flexors. The work output and peak torque were assessed during exercise. Changes in the maximal voluntary isometric contraction torque, range of motion (ROM), upper arm circumference, muscle fatigue by rating of perceived exertion, transverse relaxation time, cross-sectional area (CSA), and lactate in blood were also assessed before, immediately after, and 1 day after exercise. RESULTS: The work output during CONs in the EPA group was greater than that in the placebo group at the fifth set (EPA group; 94.0 ± 11.7%, placebo group; 82.5 ± 11.7%, p < 0.05). In addition, ROM in the EPA group was significantly greater than that in the placebo group immediately after exercise (p < 0.05). The increase of CSA in the EPA group was significantly smaller than that in the placebo group immediately after exercise (p < 0.05). CONCLUSIONS: The present study suggests that the reduction of muscle work output caused by 30 CONs can be attenuated by an 8-week EPA and DHA supplementation. In addition, EPA and DHA supplementation can cause inhibition for reduction of ROM and increase of CSA after CONs.

Two and Four Weeks of ß-Hydroxy-ß-Methylbutyrate (HMB) Supplementations Reduce Muscle Damage Following Eccentric Contractions.

OBJECTIVE: This study investigated the effect of ß-hydroxy-ß-methylbutyrate (HMB) supplementation for either 2 or 4 weeks on the muscle damage after elbow flexors after eccentric contractions (ECCs). METHODS: Twenty-eight untrained men were completed the double-blind, placebo-controlled, parallel design study. The subjects were randomly assigned to the ingestion of HMB supplement for 2 weeks (HMB 2-week, n = 10), for 4 weeks (HMB 4-week, n = 10), or a placebo group (PL, n = 8). Subjects of HMB 2-week and HMB 4-week consumed 3 g HMB per day, and they performed 6 sets of 10 ECCs at 100% maximal voluntary contraction (MVC) using a dumbbell. Changes in MVC torque, range of motion (ROM), upper arm circumference, muscle soreness, and muscle stiffness were assessed before, immediately after, and 1, 2, and 5 days after exercise. RESULTS: MVC torque and ROM were significantly higher in the HMB 2-week and HMB 4-week groups than in the PL group after ECCs (p < 0.05). The upper arm circumference was significantly smaller in the HMB 2- and 4-week groups than in the PL group after ECCs (p < 0.05). In addition, muscle stiffness at 150° was significantly lower in the HMB 2- and 4-week groups than in the PL group at immediately after ECCs (p < 0.05). However, there was no difference in all outcomes between HMB 2-week and HMB 4-week. CONCLUSION: We concluded that more than 2 weeks of HMB supplementation has a positive role for untrained subjects to prevent the muscle damage after ECCs.

Short-term cycling restores endothelial dysfunction after resistance exercise.

Resistance exercise impairs endothelial function. Therefore, it is of paramount importance to devise an effective strategy for restoring endothelial function after resistance exercise. Herein, we tested the hypothesis that resistance exercise-induced endothelial dysfunction would be restored by low-to-moderate intensity cycling. Seventeen young healthy subjects completed two randomized experimental trials: (a) resistance exercise only trial; and (b) cycling after the resistance exercise trial. Following baseline brachial artery flow-mediated dilation (FMD), subjects performed the resistance exercise. Following the resistance exercise, they were asked to rest in the supine position for the assessments of FMD. Subjects in the resistance exercise only trial maintained this supine position for 60 minutes, whereas those in the other trial cycled for 10 minutes after the resistance exercise trial. Subjects were again asked to rest in the supine position after cycling. Then FMD were repeated at 30 and 60 minutes after the resistance exercise in both trials. In the resistance exercise only trial, the increased blood flow and shear rate were disappeared after 1 hour of resting in the supine position, but were maintained in those in the cycling after the resistance trial due to subsequent cycling. Both trials caused a significant impairment in FMD at 10 minutes after the resistance exercise (P < 0.05). This decline was sustained for 60 minutes in the resistance exercise only trial. However, the impaired FMD was restored in the cycling after the resistance exercise trial. In conclusion, impaired endothelial function after the resistance exercise can be restored with 10 minutes of low-to-moderate intensity cycling.

Prior cycling exercise does not prevent endothelial dysfunction after resistance exercise.

PURPOSE: Resistance exercise impairs endothelial function acutely. Therefore, it becomes important to devise an effective strategy for preventing acute endothelial dysfunction after resistance exercise. Herein, we tested the hypothesis that resistance exercise-induced temporal endothelial dysfunction is prevented by prior cycling. METHODS: Twelve young healthy subjects completed two randomized experimental trials: (1) resistance exercise only trial (RE trial), (2) resistance exercise with prior cycling trial (C + RE trial). Following baseline brachial artery flow-mediated dilation (FMD), the subjects maintained the supine position for 45 min in the RE trial; the subjects performed a 45 min of cycling (67.0 ± 1.7% HRmax) in the C + RE trial. After 45 min of resting or cycling, the subjects performed resistance exercise (69.7 ± 4.0 kg) at the same time points. Following the resistance exercise, they were asked to rest in the supine position for 60 min. Then FMD were repeated at 10, 30 and 60 min after the resistance exercise in both trials. RESULTS: The increased blood flow and shear rate after resistance exercise did not differ between trials, and these changes disappeared following resting in the supine position for 60 min. There was no significant interaction in %FMD responses. Both trials caused impairment in %FMD after the resistance exercise, and statistical significance was observed at 30 and 60 min after resistance exercise in the RE trial. CONCLUSION: The present study revealed that cycling for 45 min prior to resistance exercise was not sufficient to prevent the acute endothelial dysfunction after resistance exercise.

High-intensity resistance exercise with low repetitions maintains endothelial function.

Resistance exercise impairs endothelial function, and this impairment is thought to be mediated by sustained elevation in blood pressure. Herein, we tested the hypothesis that resistance exercise-induced endothelial dysfunction would be prevented by high-intensity resistance exercise with low repetitions. This type of resistance exercise is known to induce temporal elevation in blood pressure due to low repetitions and a long resting period between sets. Thirteen young healthy subjects completed three randomized experimental trials as follows: 1) moderate-intensity exercise with moderate repetitions (moderate-moderate trial), 2) low-intensity exercise with high repetitions (low-high trial), and 3) high-intensity exercise with low repetitions (high-low trial). After baseline brachial artery flow-mediated dilation (FMD) and blood pressure measurements, subjects performed resistance exercise according to the different types of trials. Thereafter, brachial artery FMD and blood pressure measurements were repeated 10, 30, and 60 min after the exercise. Exercise-induced increases in blood flow and shear rate were significantly lower in the high-low trial than in the other two trials ( P < 0.05). Although systolic blood pressures were significantly elevated after exercise in all trials ( P < 0.05), the magnitudes of rise in blood pressure increase were significantly lower in the high-low trial than in the moderate-moderate and low-high trials ( P < 0.05). Moderate-moderate and low-high trials caused a significant impairment in brachial artery FMD ( P < 0.05), which could be prevented through high-intensity resistance exercise with low repetitions ( > 0.05). In conclusion, endothelial function was maintained by conducting high-intensity resistance exercise with low repetitions. NEW & NOTEWORTHY Data from the present study reveal that high-intensity resistance exercise with low repetitions can maintain endothelial function. Thus, this study provides the first evidence that the detrimental vascular effects of resistance exercise are preventable when resistance exercise is performed in high intensity with low repetitions. Listen to this article's corresponding podcast at https://ajpheart.podbean.com/e/type-of-resistance-exercise-and-endothelial-function/ (Japanese version: https://ajpheart.podbean.com/e/japanese-language-podcast-type-of-resistance-exercise-and-endothelial-function/ ).

Contralateral repeated bout effect after eccentric exercise on muscular activation.

PURPOSE: The purpose of this study was to investigate the contralateral and ipsilateral repeated bout effects of eccentric contractions (ECCs) on muscle fiber activation using transverse relaxation time (T2) of magnetic resonance imaging (MRI). METHODS: Eleven men (22.3 ± 2.9 years) performed two bouts of 30 maximal ECCs of the elbow flexors spaced 2 weeks apart. Initially, all subjects performed 30 ECCs for one arm (ECC1). After 2 weeks, they performed 30 ECCs for both ipsilateral arm (IL-RBE) and contralateral arm (CL-RBE). Measurements were maximal voluntary isometric contraction (MVC) torque, range of motion (ROM), muscle soreness, cross-sectional area (CSA), and T2 at before, immediately after, 1, 2, 3, and 5 days after ECCs. RESULTS: The loss of MVC torque, limited ROM, and developed muscle soreness and CSA were inhibited for IL-RBE and CL-RBE compared with ECC1 (p < 0.05). The acute T2, which is an indicator of the activation of muscle fibers, was longer for IL-RBE and CL-RBE than ECC1 (p < 0.05). Otherwise, no significant difference between IL-RBE and CL-RBE was observed in other measurements. CONCLUSION: Our results suggest that one of the mechanisms for CL-RBE of ECCs is the increase in muscle fiber activation. In addition, the magnitude of protective effect for CL-RBE was similar to the IL-RBE in untrained young men.

Effects of the ACTN3 R577X Genotype on the Muscular Strength and Range of Motion Before and After Eccentric Contractions of the Elbow Flexors.

The purpose of present study was to examine the association between ACTN3 R577X genotype and functional characteristics of elbow flexors before and after isokinetic eccentric contractions (ECCs). Fifty-two men (age: 20.8±3.8 years, height: 172.5±5.9 cm, body mass: 64.7±6.5 kg, BMI: 21.7±1.7) who had not participated in any regular resistance training for at least 1 year prior to this study were recruited. ECCs consisted of five sets of six maximal voluntary isokinetic (30°/s) ECCs of the elbow flexors with a range of motion (ROM) from 90° flexion to 0° (full extension). Measurements of maximal voluntary isometric contraction (MVC) torque, ROM, and muscle soreness were taken before, immediately after, and 1, 2, 3, and 5 days after ECCs. Genotyping results were analyzed for identifying ACTN3 R577X polymorphism (rs1815739) using TaqMan approach. The genotype frequencies of the ACTN3 R577X polymorphism were RR 26.9% (n=14), RX 50.0% (n=26), and XX 23.1% (n=12). There were no significant differences in MVC torque, ROM, and soreness between three genotype groups of ACTN3 R577X. However, MVC at baseline was greater in RR homozygotes than in X-allele carriers (combined XX and RX; p<0.05). ROM in RR homozygotes at baseline was lower than that of X-allele carriers. Although a significant decrease in ROM was observed in X-allele carriers until 3 days after ECCs, a significant ROM reduction in RR homozygotes was observed only immediately after ECCs. Our data indicated that ACTN3 RR genotype has higher MVC and lower flexibility than X-allele carriers at baseline, but the effect of ACTN3 R577X genotype on these two parameters is limited after ECCs.

Seasonal Variations of Bone Metabolism and Bone Mineral Density in Collegiate Alpine Skiers.

Sato, T, Sakuraba, K, Tsuchiya, Y, Maruyama, S, and Ochi, E. Seasonal variations of bone metabolism and bone mineral density in collegiate alpine skiers. J Strength Cond Res 32(5): 1448-1454, 2018-This study investigated the seasonal variations in bone metabolism, mineral density, and physical characteristics in collegiate alpine skiers. Twelve male subjects (20.6 ± 1.5 years) were evaluated for body composition, bone mineral density (BMD), serum levels of osteocalcin (OC), bone alkaline phosphatase (BAP), tartrate-resistant acid phosphatase 5b (TRACP-5b), parathormone, and 25-hydroxy vitamin D. We also measured the knee extensor and flexor strength, maximal power, and vertical jump. Measurements were conducted in the preseason period (T1), competitive period (T2), end-of-season period (T3), and resting period (T4). The percentage of body fat significantly increased from T1 to T2-T4 (p < 0.05), but lean body mass significantly decreased from T1 to T2-T4 (p < 0.05). Although BMD increased at T2 (0.9%) and T3 (0.8%), as compared with that at T1 (p < 0.05), BAP and OC decreased at T2 and T3, as compared with that at T1 (p < 0.05). Tartrate-resistant acid phosphatase 5b significantly increased from T1 to T2 (p < 0.05). We concluded that it is important to monitor bone metabolism markers and BMD of male alpine skiers throughout the season.

Differences in post-exercise T2 relaxation time changes between eccentric and concentric contractions of the elbow flexors.

PURPOSE: This study compared maximal eccentric (ECC) and concentric (CON) contractions of the elbow flexors for changes in transverse relaxation time (T2) and indirect markers of muscle damage. METHODS: Twelve young men performed five sets of six maximal isokinetic (30°/s) ECC with one arm followed by CON with the other arm. Magnetic resonance images to assess T2 and cross-sectional area (CSA) of biceps brachii, brachialis, and brachioradialis, and measurements of maximal voluntary isometric contraction (MVC) torque, range of motion (ROM), and muscle soreness were taken before, immediately after, and 1, 3, and 5 days after each exercise. RESULTS: MVC torque and ROM decreased greater after ECC than CON (p < 0.05), and muscle soreness developed only after ECC. Biceps brachii and brachialis CSA increased immediately after CON, but delayed increases in brachialis CSA were found only after ECC (p < 0.05). T2 of the muscles increased greater after CON (27-34 %) than ECC (16-18 %) immediately post-exercise (p < 0.05), but returned to baseline by 1 day after CON. The biceps brachii and brachialis T2 increased by 9-29 % at 1-5 days after ECC (p < 0.05). The post-ECC T2 changes showed no significant correlations with the changes in MVC torque, muscle soreness, and CSA, but the T2 increase immediately post-ECC was correlated with the peak T2 in 1-5-day post-ECC (r = 0.63, p < 0.05). CONCLUSION: These results suggest that muscle activity during exercise was lower in ECC than CON, and the T2 changes after ECC do not necessarily relate to the changes in other indirect markers of muscle damage.

Eicosapentaenoic and docosahexaenoic acids-rich fish oil supplementation attenuates strength loss and limited joint range of motion after eccentric contractions: a randomized, double-blind, placebo-controlled, parallel-group trial.

PURPOSE: This study investigated the effect of eicosapentaenoic and docosahexaenoic acids-rich fish oil (EPA + DHA) supplementation on eccentric contraction-induced muscle damage. METHODS: Twenty-four healthy men were randomly assigned to consume the EPA + DHA supplement (EPA, n = 12) or placebo (PL, n = 12) by the double-blind method. Participants consumed EPA + DHA or placebo supplement for 8 weeks prior to exercise and continued it until 5 days after exercise. The EPA group consumed EPA + DHA-rich fish oil containing 600 mg EPA and 260 mg DHA per day. Subjects performed five sets of six maximal eccentric elbow flexion exercises. Changes in the maximal voluntary contraction (MVC) torque, range of motion (ROM), upper arm circumference, muscle soreness as well as serum creatine kinase, myoglobin, IL-6, and TNF-α levels in blood were assessed before, immediately after, and 1, 2, 3, and 5 days after exercise. RESULTS: MVC was significantly higher in the EPA group than in the PL group at 2-5 days after exercise (p < 0.05). ROM was also significantly greater in the EPA group than in the PL group at 1-5 days after exercise (p < 0.05). At only 3 days after exercise, muscle soreness of the brachialis was significantly greater in the PL group than in the EPA group (p < 0.05), with a concomitant increase in serum IL-6 levels in the PL group. CONCLUSION: Eight-week EPA + DHA supplementation attenuates strength loss and limited ROM after exercise. The supplementation also attenuates muscle soreness and elevates cytokine level, but the effect is limited.