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Abstract Backgroud While serum levels of hyarulonic acid (sHA) is known to be useful for a burden of disease biomarker in knee OA, it is far from practical. The reference intervals must be established for biomarkers to be useful for clinical interpretation. The aim of this study was to establish the reference intervals of sHA corresponding to the radiographic severity of knee OA for elucidating whether sHA can be useful as a burden of disease marker for individual patient with knee OA. Methods 372 women with Kellgren & Lawrence grade (K/L) 1 through 4 painful knee OA were enrolled in this study. The patients included 54 with K/L 1, 96 with K/L 2, 97 with K/L 3, and 118 with K/L 4. Serum samples were obtained from all subjects on the day that radiographs taken. A HA binding protein based latex agglutination assay that employed an ELISA format was used to measure sHA. Age and BMI adjusted one way ANOVA was used to set the reference intervals of sHA. Results The reference intervals for sHA corresponding to the patients with K/L 4 (49.6 – 66.5 ng/ml) was established without any overlap against to those with K/L 1, 2 and 3, while those with K/L 1, 2 and 3 showed considerable overlap. Conclusions These results indicate that sHA can be available as a burden of disease marker for the individuals with severe knee OA (K/L 4), while it is not for those with primary to moderate knee OA (K/L 1–3).

Objective: Quantifying and managing the matches and training loads of players is important for injury prevention. As rugby union is a full-contact sport and frequent contact injuries occur, it might also be important to quantify and manage players' contact loads. This study aimed to clarify the relationship between contact load and injury incidence in elite rugby union players., Methods: Forty-eight elite rugby union players (27.0 ± 3.5 years) in Japan were monitored during one season (8 months). The contact load, an index of training load, was evaluated as collision count and collision load measured using a global positioning system device, and then calculated using the acute:chronic workload ratio (ACWR) based on the exponentially weighted moving average (EWMA). The association between the EWMA-ACWR of contact load and injury incidence was analyzed using generalized estimating equations., Results: Of the 58 injuries during one season, 70.7% were contact injuries. Collision counts and collision load calculated by EWMA-ACWR were associated with the risk of injury ( p  < 0.01 both), with the odds ratios were 4.20 [95% confidence interval (CI): 1.74-10.11] and 4.44 (95% CI: 1.95-10.13), respectively., Conclusion: Contact load calculated using EWMA-ACWR was associated with injury in elite rugby union players., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (© 2024 Iwasaki, Someya, Nagao, Nozu, Shiota and Takazawa.)

Purpose: A short period of disuse of 1-2 weeks due to factors such as illness or injury can lead to muscle atrophy, affecting both athletic performance and health. Recent research has shown that uridine 5'-monophosphate (5'-UMP) can counteract disuse-induced muscle atrophy by increasing PGC-1α expression and inhibiting atrogin-1 expression. However, the effect of 5'-UMP on disuse muscle atrophy in humans remains unknown. Therefore, the aimed of this study was to explore the effects of 5'-UMP supplementation during detraining on short-term disuse muscle atrophy in healthy men., Methods: Following a 6-week resistance training program on upper arm, healthy men were randomized to either a UMP group ( n  = 11) or a placebo group ( n  = 10), taking their respective supplements during the 2-week detraining period. Muscle thickness, an indicator of muscle hypertrophy and atrophy, was measured at 3 positions (MT50, MT60, and MT70) at baseline, 1 week, and 2 weeks after detraining., Results: Both groups showed a significant decrease in muscle thickness at MT70. The relative decrease was greater in the placebo group (2.4 ± 2.8%) than in the UMP group (0.0 ± 2.0%), significantly ( p  = 0.034) at 1 week. However, no significant difference was observed at MT50 and MT60., Conclusion: After the hypertrophy, 5'-UMP may prevent muscle atrophy due to the detraining within the first week., Competing Interests: KN and KI, are employees of YAMASA Corporation (Chiba, Japan) which funded this study; they had responsibility of the test supplements but did not involve in the investigation, formal analysis, and data curation. The results of the study are presented clearly, honestly, and without fabrication, falsification, or inappropriate data manipulation. The remaining authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (© 2024 Inoue, Kubota, Takazawa, Nakagawara, Ishige and Suzuki.)

Objectives: This study aimed to determine the effects of high-intensity isokinetic training with blood flow restriction during rest interval between set (rBFR) versus during exercise (eBFR) on muscle hypertrophy and increasing muscle strength and determine whether BFR-induced exercise pain is suppressed by rBFR., Materials and Methods: Fourteen arms (7 participants) were recruited for the study. We conducted the following interventions for each arm: eBFR (n=4), rBFR (n=5), and exercise only (CON, n=5). The participants performed elbow flexion training with a BIODEX device twice weekly for 8 weeks. This study training consisted of total four sets; each was performed until <50% peak torque was achieved twice consecutively. BFR pressure was set at 120 mmHg. Elbow flexor peak torque during concentric contraction (CC), isometric contraction (IM), and muscle cross-sectional area (CSA) were measured before and after the intervention. Numerical rating scale scores used to assess pain during exercise were determined during training., Results: Peak torque at the CC increased in the rBFR (p<0.05) and IM increased in the rBFR and CON (p<0.05), while CSA increased in the rBFR and CON (p<0.001). The pain during exercise was severe in the eBFR and moderate in the rBFR and CON., Conclusions: This study's showed that high-intensity isokinetic training with rBFR did not have a synergistic effect on increasing muscle strength and muscle size. Additionally, high-intensity isokinetic training with BFR when it may be best not to perform it during exercise, because it was induces severe pain and may inhibit increases in muscle strength., Competing Interests: The authors have no competing interests to declare that are relevant to the content of this article and did not receive support from any organization for the submitted work., (© 2023 The Juntendo Medical Society.)

Objectives: This study aimed to investigate the effects of drinking oxygenated water on oxygen saturation during exercise under normobaric hypoxic conditions., Materials: A randomized placebo-controlled single-blinded trial was performed. Twenty-two healthy adults (16 men and 6 women), with a mean age (standard deviation) of 22.4 (2.73) years, participated in the study. The participants were randomly assigned to one of two groups: an OX group (drinking oxygenated mineral water) and a control group (drinking normal mineral water). Both groups performed walking exercises under normobaric hypoxic conditions. Blood oxygen saturation (SpO 2 ), pulse rate (PR), and walking distance were measured during exercise., Results: SpO 2 decreased and PR increased during exercise in both groups. The decrease in SpO 2 was smaller and the increase in PR was greater in the OX group compared with those in the control group. No significant difference was found in walking distance between the two groups., Conclusions: Drinking oxygenated water before exercise may inhibit SpO 2 reduction under normobaric hypoxic conditions., Competing Interests: WellsO2 Inc funded this study. However, none of the authors were employees of the company nor received any honoraria., (© 2022 The Juntendo Medical Society.)

The purpose of this study was to investigate the preoperative characteristics that are necessary to be able to perform reconstructions of the anterior cruciate ligament (ACL) with remnant preservation. The preoperative period was significantly shorter for patients in patients who received a reconstruction with remnant preservation than for those without remnant (3.9 months vs 16.0 months, p < 0.01). The cut-off time to be able to reconstruct an ACL with remnant preservation were 2.5 months. The preoperative period is important to perform an ACL reconstruction with remnant preservation.