Kiyokazu Akasaka

Background: Repetitive pitching causes temporary functional impairment of the medial elbow. The recovery process in medial elbow dynamic stabilizing mechanisms is not clear. Hypothesis/Purpose: This study aimed to investigate the recovery process of the medial elbow dynamic stabilizers over 24 hours after 100 pitches. We hypothesized that while some recovery occurs 24 hours after pitching, there would not be a complete return to baseline. Study Design: Descriptive laboratory study. Methods: A total of 26 high school baseball pitchers participated in this study (mean age, 16 ± 0.5 years). Participants pitched 100 times (5 blocks of 20 pitches). Medial elbow joint width and strain ratio (higher values indicate harder tissue) of the ulnar collateral ligament (UCL) and forearm flexor-pronator muscles (FPMs) under FPM contraction associated with gripping were measured at baseline, immediately after pitching, and at 1, 3, 6, 18, and 24 hours after pitching. The data before pitching and at each measurement time point were compared. Results: Medial elbow joint width during contraction significantly increased immediately after pitching ( P < .05), but this was not maintained at 24 hours. The UCL strain ratio during contraction significantly decreased immediately after pitching ( P < .05), but this was not maintained 18 hours after pitching. The FPMs strain ratio during contraction showed no significant change over time ( P = .747). Conclusion: After 100 pitches, resistance to elbow valgus laxity associated with FPMs contraction temporarily decreases but recovers 24 hours after pitching. In addition, the UCL becomes temporarily vulnerable but recovers by 18 hours after pitching. Clinical Relevance: Baseball pitchers may be allowed to throw low-intensity pitches 24 hours after a pitching session from the perspective of a restoration in dynamic stability. However, rather than determining pitching eligibility based solely on a uniform number of pitches or rest days, objective assessment incorporating medial elbow stabilizing indices may support individualized determination of when to resume pitching.

Introduction: Hip abductor dysfunction is associated with various musculoskeletal disorders, such as knee overuse injury, patellofemoral pain syndrome, and hip osteoarthritis. Thus, hip abduction exercise is used to improve hip muscle performance. Notably, deep hip muscles might be effectively activated during the hip internal rotation (IR) position. Moreover, it is hypothesized that hip abduction combined with hip IR might activate the deep hip muscles and minimize tensor fascia latae (TFL) activation. Objective: This study aimed to investigate the percentage maximum voluntary isometric contraction (%MVIC) and the activity ratio of the gluteus muscles in relation to the activity of the TFL—including the gluteus minimus (GMin), piriformis, and gluteus medius (GMed)—across different hip positions during side-lying hip abduction. Methods: Twelve healthy men performed hip abduction exercises in nine hip joint positions. The muscle activities of the lower extremities, including the anterior and posterior segments of the GMin (GMin-a and GMin-p) and piriformis, GMed, and TFL, were recorded via surface and fine-wire electromyography. Results: The %MVIC of the GMin-p and GMed was highest in hip extension and IR (EIR) position during the late concentric phase (GMin-p 54.7 ± 27.2 %MVIC; GMed 59.2 ± 36.1 %MVIC; P < 0.05). No significant difference was observed in the %MVIC of TFL (lower in the hip internal rotation position). The relative activation ratios (RARs) of the GMin-p and GMed to TFL were highest in hip position involving IR during the early concentric or late eccentric phases (GMin-p 3.80 ± 3.65; GMed 2.62 ± 1.72; <0.05). Conclusions: Hip abduction during the late concentric phase with EIR position caused maximal hip abductor activity. Conversely, hip abduction during the early concentric phase involving the IR position selectively activated the GMin-p and GMed while minimizing TFL activation.

Background: Thoracic spine mobility is essential for optimal pitching mechanics and injury prevention in baseball players. While shoulder and hip range of motion (ROM) changes after pitching have been reported, there is a lack of evidence regarding immediate changes in thoracic spine ROM after pitching. Objective: To investigate the immediate effects of repetitive pitching on thoracic spine extension and rotation ROM in high school baseball players and to identify which assessment method is most sensitive to these changes. Design: Randomized controlled trial. Setting: High school baseball fields. Participants: Thirty‐four male high school baseball players were randomly assigned to a pitching group ( n = 17) or a control group ( n = 17). Players with prior elbow surgery or recent injuries were excluded. Interventions: The pitching group performed 100 maximum‐effort fastballs, and the control group rested for an equivalent duration. Main outcome measures: Thoracic kyphosis angle, upper and lower trunk extension ROM, total trunk extension ROM, and six thoracic mobility tests were assessed before and after the intervention. The primary outcome was dominant‐side thoracic rotation ROM measured by the side‐lying rotation test. Results: A significant group × time interaction was observed for dominant‐side rotation in the side‐lying rotation test ( p = .015). Post hoc analysis revealed a significant increase in ROM after pitching in the pitching group (mean difference [pre–post] = −3.4°; p = .004; 95% CI: −5.675 to −1.266). No statistically significant correlation was found between ball velocity and dominant‐side rotation ROM ( r = 0.454, p = .067), although a moderate‐to‐large effect size was observed. Conclusions: Repetitive pitching acutely increases thoracic rotation ROM toward the throwing side in high school baseball players, detectable by the side‐lying rotation test. This test may serve as a practical tool to monitor pitching‐induced mobility changes relevant to performance and injury prevention.

Background: Shoulder function asymmetries are common in adolescent volleyball players, yet evidence beyond glenohumeral range of motion (ROM) is limited, and few studies jointly examine sex and attack form. Hypothesis: Shoulder asymmetries would differ by attack form, with bow-and-arrow hitters showing greater dominant-nondominant internal rotation (IR) strength and dynamic-stability asymmetry than straight-arm hitters. Second, we expected typical dominant-arm ROM and strength adaptations and greater strength and stability in boys than girls. Study Design: Cross-sectional study. Level of Evidence: Level 3. Methods: We evaluated 108 high school volleyball players (49 boys, 59 girls). Bilateral shoulder ROM, isometric strength, joint position sense, acromiohumeral distance, and dynamic stability (upper quarter Y-balance test [UQYBT]) were assessed. Asymmetry was defined as dominant minus nondominant. Exploratory logistic regression examined associations between attack form (straight vs bow-and-arrow/circular) and shoulder asymmetry, with an additional exploratory female-only subgroup analysis. Results: Both sexes showed marked dominant-side adaptations: reduced IR ROM (boys −20.3°, girls −17.6°; both P < 0.001) and increased external rotation (ER) ROM (boys 11.7°, girls 7.7°; both P < 0.001), with decreased total rotational motion. Boys had higher normalized IR and ER strength ( P < 0.001) and superior UQYBT performance ( P < 0.001), except inferolateral. In exploratory logistic regression, greater IR strength asymmetry (odds ratio [OR], 1.18; 95% CI, 1.01-1.40; P = 0.04) and smaller inferolateral reach asymmetry (OR, 0.92; 95% CI, 0.86-0.98; P = 0.01) were associated with using a bow-and-arrow/circular swing; however, no significant attack-form differences were observed in the exploratory female-only subgroup analysis. Conclusion: Characteristic overhead-shoulder profiles - IR loss, ER gain, and preserved ER/IR ratios - are already present in high school volleyball players. Associations between attack form and shoulder asymmetry should be interpreted cautiously and considered exploratory. Clinical Relevance: Clinicians may monitor IR ROM, strength balance, and upper-quarter stability to characterize shoulder function in adolescent volleyball players and to identify extreme or symptomatic asymmetries that may warrant individualized conditioning.

To evaluate whether 100 consecutive pitches induce clinically meaningful increases in medial elbow joint space gap (MJS) in high school baseball players and to examine associations with player characteristics, including early multi-sport participation. In a randomized controlled trial, 34 healthy male high school baseball players were allocated to a pitching group (n = 17) or a control group (n = 17). The pitching group threw 100 fastballs at maximal effort, whereas controls rested for an equivalent duration. MJS was measured by ultrasonography before and after pitching or rest. The minimal clinically important difference (MCID) for MJS change (mm and %) was calculated using a distribution-based method (0.5 × SD of the pitching group's MJS increase). Group × time effects were tested using a two-way repeated-measures ANOVA, and univariate analyses explored relationships between MJS change and participant characteristics. No significant group × time interaction was observed (p = 0.427). In the pitching group, MJS increased by 0.2 ± 1.1 mm (8.3 ± 24.6%), remaining below the MCID thresholds (0.55 mm; 12.3%). Early multi-sport experience during elementary school was associated with smaller MJS expansion (p = 0.009), and the number of non-baseball sports correlated negatively with MJS change (r = -0.628, p = 0.007). No associations were found with pitch velocity or body composition. A single bout of 100 pitches did not produce clinically meaningful MJS widening in high school baseball players. However, early multi-sport participation was related to reduced MJS expansion, suggesting that diversified sport experience may be an important background factor when refining pitch-count guidance.

Background and Aims: The measurement properties of the Japanese Oswestry Disability Index (ODI) and the effects of site‐specific pain and numbness on disability in preoperative patients with lumbar spinal stenosis (LSS) remain insufficiently explored. This study aimed to evaluate the factor structure and reliability of the ODI and examine the influence of pain and numbness on disability. Methods: A total of 147 preoperative patients with LSS aged 60 and above, scheduled for lumbar spine surgery, were included. Demographic and clinical data, including pain and numbness levels using the numerical rating scale (NRS), were collected. We excluded the sexual life item from the ODI, and the analysis was conducted using the remaining nine items. This exclusion was considered in the interpretation of the measurement properties. Exploratory factor analysis (EFA), Cronbach's α , and regression analysis were used to evaluate the factor structure, reliability, and the effect of symptoms on disability. Results: The sample (mean age 73.3 years) included 72.1% males. The mean ODI score was 46.8% (“severe disability”). EFA identified two latent factors: Daily living (e.g., personal care, sitting, sleeping) and Social living (e.g., traveling, social activities), with a moderate inter‐factor correlation ( r = 0.62). Cronbach's α indicated high internal consistency (0.8 for daily living and social living). In the multivariable regression analyses, low back pain ( β = 0.33, p < 0.001), leg pain ( β = 0.22, p = 0.006), and foot pain ( β = 0.17, p = 0.02) were significantly associated with the Daily living factor, whereas low back pain ( β = 0.22, p = 0.01) and leg pain ( β = 0.20, p = 0.02) were significantly associated with the Social living factor. Numbness showed weaker associations with both factors. Conclusions: The Japanese ODI is a reliable tool for assessing disability in preoperative patients with LSS, with distinct factors for daily and social functioning. Pain management for the low back, leg, and foot may play an important role in optimizing patient care.

Injury prevention programs for adolescent athletes include pre-game exercise programs designed to improve individuals physical function. This study aimed to determine the impact of Golfers’ Low back pain Exercise prevention Program (GLEP) on physical function and golf performance. A total of 45 adolescent golfers participated in this double-blind, randomized, sham-controlled trial. Participants were randomly assigned to the GLEP or sham exercise program. Physical function and golf performance was measured at baseline, 4-week, 8-week, and 12-week. Measurements included hip rotation, trunk lateral flexion and rotation range of motion (ROM), hip external rotation (ER) muscles strength, trunk endurance, and golf performance. Data were compared before the intervention and at each measurement point. Statistical analysis consisted of a mixed-model analysis of variance. Both hip rotation ROM and trunk endurance improved significantly over time in both groups (p < .001). No significant effects were observed for trunk lateral flexion and rotation ROM (p > .05). Lead hip ER muscle strength showed a significant interaction, with greater values in the GLEP group (p = .017). There was no significant difference in golf performance measures between groups (p > .05). The addition of a pre-game exercise program for adolescent golfers may have the potential to affect hip ROM and trunk endurance without negatively impacting performance. The GLEP significantly improved lead hip ER muscle strength when compared to a sham. The GLEP is an effective pre-game exercise program for golfers seeking to enhance hip ER strength. This study was registered in the UMIN Clinical Trials Registry as a clinical trial (ID: UMIN000051318; registration date: 01/08/2023).

Background: Groin pain in soccer players arises from various causes, most commonly kicking, and as such can significantly affect performance. A new form of exercise, the cross-motion swing exercise (CMS), may help prevent groin pain but is untested. Purpose: To evaluate the effectiveness of the CMS in preventing groin pain in high school soccer players. Study Design: Randomized controlled trial; Level of evidence, 1. Methods: This study involved 135 male high school soccer players P = .028). The number of injuries was 6 in the intervention group and 18 in the control group, and injuries due to the kicking motion were 0 in the intervention group (0%) and 7 in the control group (38.9%). Conclusion: The CMS significantly reduced the incidence of groin pain in high school soccer players. This suggests that coordination-based exercise, closely mimicking the appropriate sports-specific movement, was effective in reducing injury. The study supports incorporating the CMS into regular training to reduce the incidence of groin pain in male high school soccer players. Trial Registry and the Registration Number: This study has been registered as a clinical trial with the Universal Medical Information Network (UMIN) under the registration number UMIN000051311.

Context: Nontraumatic shoulder pain (NSP) is common in volleyball, affecting performance and well-being. It is more prevalent in female players. Previous studies lack comprehensive assessments of shoulder pain that consider multiple factors, including range of motion, muscle strength, joint position sense, dynamic stability, and volleyball-specific mechanics. Objective: To investigate NSP prevalence in female high school volleyball players, considering shoulder joint functional parameters and volleyball-specific factors. Design: Cross-sectional study. Setting: High school gymnasiums. Patients or Other Participants: Fifty-nine female high school volleyball players (15–17 years). Main Outcome Measure(s): Demographic data, environmental factors (years of experience, spiking technique, and serve type), shoulder joint function (passive glenohumeral joint’s range of motion, muscle strength, joint position sense, and dynamic stability), and NSP prevalence during spiking and serving. Logistic regression analysis was conducted to identify significant factors associated with NSP. Results: Nontraumatic shoulder pain prevalence was 54.2%, with 68.8% not informing coaches. Significant associations were found between NSP and factors such as Upper Quarter Y-Balance Test-Medial (P = .008; odds = 0.892; 95% confidence interval = 0.82, 0.97) and joint position sense of internal rotation (P = .031; odds = 1.411; 95% confidence interval = 1.03, 1.93). Conclusion: Shoulder pain leads to impaired proprioception and dynamic stability. Effective communication between players and coaches is crucial for managing and preventing pain. Targeted training programs to enhance proprioception and dynamic stability may reduce shoulder pain and injuries. Educating players on the importance of reporting pain and encouraging early intervention is essential.