Shumpei Miyakawa

Lumbar Intervertebral Disk Degeneration in Athletes

Background Several studies have reported that physical loading related to competitive sports activities is associated with lumbar intervertebral disk degeneration. However, the association between types of sports activities and disk degeneration has not been clarified. Hypothesis The frequencies of disk degeneration may vary with the competitive sport because of the different postures and actions specific to each sport. Study Design Cross-sectional study (prevalence); Level of evidence, 3. Methods Study participants were 308 well-trained university athletes (baseball players, basketball players, kendo competitors, runners, soccer players, swimmers) and 71 nonathlete university students (reference group). Disk degeneration was evaluated using T2-weighted magnetic resonance imaging. A self-reported questionnaire concerning low back pain was also conducted. Results The proportions of the participants who had disk degeneration among the baseball players (odds ratio, 3.23) and the swimmers (odds ratio, 2.95) were significantly higher than among the nonathletes using logistic regression analysis. When all patients were grouped together, the association between lifetime experience of low back pain and participants with disk degeneration was significant, and a linear association between the degree of severest low back pain experienced and participants with disk degeneration, analyzed by a Cochran-Mantel-Haenszel test, was also significant. Conclusion Continuous competitive baseball and swimming activities during youth may be associated with disk degeneration. Furthermore, the study indicates that the experience of severe low back pain might be a predictor of disk degeneration in youth. The authors hope that preventive measures and management to protect against disk degeneration and low back pain in athletes will be established by further studies based on these results.

Relationship Between Low Back Pain and Competitive Sports Activities During Youth

Background Low back pain is a significant problem not only for the adult, but also during youth. However, the relationship between low back pain during youth and the duration or types of competitive sports has not been clarified. Hypothesis Low back pain during youth is associated with the duration and types of competitive sports. Study Design Cross-sectional study; Level of evidence, 4. Methods Study participants were 4667 new university students who, from 2004 to 2006, answered a questionnaire concerning low back pain and their participation in competitive sports. The participants were divided into a “no” group (NO), a middle group (MID), and a high group (HI) based on the duration of participation in competitive sports. The answers to the questionnaire were analyzed using the Cochran-Mantel-Haenszel test. Furthermore, we selected students who had participated in the same sport for 5 or more years and categorized the students according to the type of sport. Differences in low back pain among the groups were analyzed using logistic regression with the NO group as the reference group. Results There were statistically significant linear associations in the NO, MID, and HI groups, with 50.0%, 61.8%, and 71.7%, respectively, of the students experiencing low back pain. Among the NO, MID, and HI groups, 4.4%, 5.7%, 9.6%, respectively, had experienced school absence due to low back pain; and 4.0%, 8.5%, and 14.6%, respectively had low back pain with associated lower extremity pain and numbness. All 8 sports groups that were analyzed had experienced low back pain significantly higher than the NO group, and the odds ratios differed by sport with the highest (3.8) for the volleyball group. Conclusion Excessive exposure to competitive sports activities during youth was associated with low back pain and symptoms in the lower extremities, with the severity varying with the sport. To reduce low back pain in youth, factors that may be causing low back pain, such as sport-specific postures and motions, need to be investigated.

Pilot study: Effects of drinking hydrogen-rich water on muscle fatigue caused by acute exercise in elite athletes

BackgroundMuscle contraction during short intervals of intense exercise causes oxidative stress, which can play a role in the development of overtraining symptoms, including increased fatigue, resulting in muscle microinjury or inflammation. Recently it has been said that hydrogen can function as antioxidant, so we investigated the effect of hydrogen-rich water (HW) on oxidative stress and muscle fatigue in response to acute exercise.MethodsTen male soccer players aged 20.9 ± 1.3 years old were subjected to exercise tests and blood sampling. Each subject was examined twice in a crossover double-blind manner; they were given either HW or placebo water (PW) for one week intervals. Subjects were requested to use a cycle ergometer at a 75 % maximal oxygen uptake (VO2) for 30 min, followed by measurement of peak torque and muscle activity throughout 100 repetitions of maximal isokinetic knee extension. Oxidative stress markers and creatine kinase in the peripheral blood were sequentially measured.ResultsAlthough acute exercise resulted in an increase in blood lactate levels in the subjects given PW, oral intake of HW prevented an elevation of blood lactate during heavy exercise. Peak torque of PW significantly decreased during maximal isokinetic knee extension, suggesting muscle fatigue, but peak torque of HW didn’t decrease at early phase. There was no significant change in blood oxidative injury markers (d-ROMs and BAP) or creatine kinease after exercise.ConclusionAdequate hydration with hydrogen-rich water pre-exercise reduced blood lactate levels and improved exercise-induced decline of muscle function. Although further studies to elucidate the exact mechanisms and the benefits are needed to be confirmed in larger series of studies, these preliminary results may suggest that HW may be suitable hydration for athletes.

Effects of Taurine Administration on Exercise

Taurine concentration in rat skeletal muscles after endurance running, with and without taurine administration was studied. Taurine concentrations in skeletal muscles was significantly decreased in exercised groups without taurine administration. However, taurine administration reduced the decrease of taurine concentration in skeletal muscles in exercise. Oral administration of taurine has effect for maintaining taurine concentration in skeletal muscles in exercise. The duration of running time to exhaustion of rats, with and without taurine administration were studied. The duration of running time to exhaustion was significantly increased by taurine administration. Oral administration of taurine increases the ability of physical endurance. Rat urinary excretions of creatinine, creatine, 3-methylhistidine (3-MH) after treadmill running, with and without taurine administration were studied. Rat urinary excretions of creatinine, creatine, 3-MH after treadmill running was significantly decreased with taurine administration. Taurine administration was considered to reduce the exercise-induced muscle fatigue.

Enhancement of satellite cell differentiation and functional recovery in injured skeletal muscle by hyperbaric oxygen treatment

Recently, the use of hyperbaric oxygen (HBO) treatments by elite athletes to accelerate recovery from muscle injuries has become increasingly popular. However, the mechanism of promoting muscle regeneration under HBO conditions has not yet been defined. In this study, we investigated whether HBO treatments promoted muscle regeneration and modulated muscle regulatory factor expression in a rat skeletal muscle injury model. Muscle injury was induced by injecting cardiotoxin (CTX) into the tibialis anterior (TA) muscles. As the HBO treatment, rats were placed in an animal chamber with 100% oxygen under 2.5 atmospheres absolute for 2 h/day, 5 days/wk for 2 wk. We then performed histological analyses, measured the maximum force-producing capacity of the regenerating muscle fibers, and performed quantitative RT-PCR analysis of muscle regulatory factor mRNAs. The cross-sectional areas and maximum force-producing capacity of the regenerating muscle fibers were increased by HBO treatment after injury. The mRNA expression of MyoD, myogenin, and IGF-1 increased significantly in the HBO group at 3 and 5 days after injury. The number of Pax7(+)/MyoD(+), Pax7(-)/MyoD(+), and Pax7(+)/BrdU(+)-positive nuclei was increased by HBO treatment. In this study, we demonstrated that HBO treatment accelerated satellite cell proliferation and myofiber maturation in rat muscle that was injured by a CTX injection. These results suggest that HBO treatment accelerates healing and functional recovery after muscle injury.

Metabolomics of salivary fatigue markers in soccer players after consecutive games

Strenuous and consecutive exercise leads to fatigue symptoms in athletes. Metabolomics is a comprehensive method to assess metabolites that involves the measurements of the overall metabolic signature of biological samples. Using metabolomic analysis, we investigated the identification of salivary fatigue markers in soccer players after 3 consecutive days of a game program. One hundred twenty-two male soccer players participated in 3 consecutive days of a game program. To detect fatigued athletes, we measured indices of traditional fatigue symptoms, i.e., heart rate, body mass and mood, before and after the program. We detected 37 fatigued players throughout the program. Before and after the program, the saliva in these players was analyzed using capillary electrophoresis and time-of-flight mass spectrometry (CE-TOFMS) and a multivariate statistical technique, principal component analysis, was used to process the data. CE-TOFMS was used to identify 144 metabolites in the saliva of fatigued players. A significant metabolomic difference was observed before and after 3 consecutive days of a soccer game program. Interestingly, metabolites were all increased after the program (P < 0.001). The identified metabolites, including 3-methylhistidine, glucose 1- and 6-phosphate, taurine, and some amino acids, were involved in skeletal muscle catabolism, glucose metabolism, lipid metabolism, amino acid metabolism, and energy metabolism. Our work demonstrated some salivary metabolites were significantly increased in the fatigued players after consecutive days of short soccer matches. We propose that the detected salivary metabolites may be new fatigue markers in athletes.

The harmful effect of exercise on reducing taurine concentration in the tissues of rats treated with CCl4 administration.

BackgroundWe have previously reported that oral taurine administration reduced the frequency of painful muscle cramps in patients with liver cirrhosis, and that skeletal muscle taurine concentration was significantly decreased after exercise. The aim of this study was to examine taurine concentration in various tissues of a liver damaged with fibrosis (LD) in a rat model before and after exercise.MethodsRats were divided into normal (NML) and LD groups. The LD group received CCl4 injection for 10 weeks. Thereafter, both groups were divided into control (NML/CTL, LD/CTL) and exercise (NML/EX, LD/EX) groups, respectively. The rats in the EX groups were subjected to treadmill running. Plasma, liver, brain, heart, and skeletal muscle taurine concentration, as well as plasma and liver lipid peroxidase (LPO) concentration, were measured.ResultsThe liver, brain, and skeletal muscle taurine concentration in the LD groups was significantly decreased compared to that in the respective NML groups. Furthermore, the taurine concentration in the heart and skeletal muscles in the LD/CTL group was significantly decreased post exercise. The respective plasma and liver LPO concentration in the LD groups was significantly increased compared to that in the corresponding NML group. Moreover, plasma LPO concentration in the LD/EX group was significantly higher than in the LD/CTL group.ConclusionsTissue taurine concentration, particularly in skeletal muscle, was significantly decreased in the LD model rats induced by CCl4 administration, and furthermore, the significantly decreased concentration, except for liver, was aggravated by exercise, even though at lower intensity.

Critical factors for the prevention of low back pain in elite junior divers

Background/Aim During competitive diving, divers jump up from 1 to 3 m springboards or 5 to 10 m platforms and dive into the water. The impact forces are very large in the water entry phase, and, as such, microtraumatic injuries are common due to the tremendous physical stress placed on the diver. Low-back pain (LBP) is the most frequently reported symptom in divers. This study aimed to extract possible risk factors related to LBP from physical and technical characteristics in Japanese elite junior divers. Methods Eighty-three elite junior divers (42 men and 41 women) in Japan were included in this study. LBP was assessed by a questionnaire, interview and physical examination during a national training camp. Morphological data, physical fitness and diving skills were also evaluated. The factors related to LBP were extracted by using logistic-regression analysis and the forward-selection method (likelihood ratio). Results A total of 37.3% (31 reports) of back pain occurred in the lumbar region. Shoulder flexibility (OR 0.919; 95% CI 0.851 to 0.992) and age (OR 0.441; 95% CI 0.239 to 0.814) were recognised as factors related to LBP in male-elite junior divers, whereas only age (OR 0.536; 95% CI 0.335 to 0.856) was a factor in female-elite junior divers. Conclusions Our results suggest that shoulder flexibility is important for preventing LBP in elite-male junior divers, since they require full shoulder flexion during the water entry phase. Limited shoulder flexibility could cause lumbar hyperextension when adjusting for the angle of water entry.

Cross-cultural adaptation, reliability, and validity of the Japanese version of the Cumberland ankle instability tool

Abstract Purpose To study validity and reliability of a Japanese version of the Cumberland Ankle Instability Tool and to determine the optimal cutoff score. Methods In this study, the questionnaire was cross-culturally adapted into Japanese. The psychometric properties tested in the Japanese version of the CAIT were measured for criteria validity, internal consistency and test–retest reliability in 111 collegiate soccer athletes. We also established the questionnaire cutoff score for discriminating between individuals with and without CAI. Results There was a significant correlation between the Japanese version of the CAIT and the Karlsson score (r = 0.604, p < 0.001). The questionnaire had a high internal consistency (Cronbach’s α = 0.833) and reliability [intraclass correlation coefficient (ICC) = 0.826, 95% confidence interval (CI): 0.732–0.888]. The optimal cutoff score was ≤25, which was consistent with previous reports. Conclusions The Japanese version of the CAIT has been shown to be a valid and reliable questionnaire for determining the presence of CAI. We expect that researchers and clinicians will use the Japanese version of the CAIT in Japan. Implications for Rehabilitation Chronic Ankle Instability (CAI), which not only increases recurrence rate of ankle sprain but also decreases athletic performance, is a residual symptom after ankle sprain. Cumberland Ankle Instability Tool, which has the reliability and validity to assess CAI, will be critically useful in assessment procedure for CAI. It is preferable for clinicians and researchers to use the native language version of the CAIT.

COMPARISON OF THE ACTIVITIES OF THE DEEP TRUNK MUSCLES MEASURED USING INTRAMUSCULAR AND SURFACE ELECTROMYOGRAPHY

Surface electromyography (EMG) has been used to estimate deep trunk muscle activity. However, it remains unknown whether surface EMG provides an accurate estimation of this activity. The purposes of this study were to compare surface and intramuscular EMG activity measurements and investigate the efficacy of surface EMG measurement for the transversus abdominis (TrA) and the multifidus (MF) muscles. Eight healthy men participated in the study. TrA and MF activities were simultaneously measured by both intramuscular and surface EMG during isometric trunk exercises. Spearman correlation coefficients for the relationship between the two activity measurements for the right TrA, left TrA, right MF, and left MF were 0.55, 0.36, 0.67, and 0.79, respectively. For the TrA, Bland–Altman plots revealed that mean differences between measurements obtained by intramuscular EMG and surface EMG were not close to zero, with a systematic bias toward higher surface EMG values. In conclusion, surface and intramuscular EMG ac...