Trunk Rotation Strength Research Articles

Performance on the Single-Leg Squat Task Indicates Hip Abductor Muscle Function

Background: Contemporary clinical expertise and emerging research in anterior knee pain indicate that treatment of hip muscle function will result in greater effects, if such treatments can be provided to those with hip muscle dysfunction. Thus, it is imperative to develop and evaluate a clinical assessment tool that is capable of identifying people with poor hip muscle function. Hypothesis: The clinical assessment of single-leg squat performance will have acceptable inter- and intrarater reliability. Furthermore, people with good performance on the single-leg squat will have better hip muscle function (earlier onset of gluteus medius activity and greater lateral trunk, hip abduction, and external rotation strength) than people with poor performance. Study Design: Cohort study (diagnosis); Level of evidence, 2. Methods: A consensus panel of 5 experienced clinicians developed criteria to rate the performance of a single-leg squat task as “good,” “fair,” or “poor.” The panel rated the performance of 34 asymptomatic participants (mean ± SD: age, 24 ± 5 y; height, 1.69 ± 0.10 m; weight, 65.0 ± 10.7 kg), and these ratings served as the standard. The ratings of 3 different clinicians were compared with those of the consensus panel ratings (interrater reliability) and to their own rating on 2 occasions (intrarater reliability). For the participants rated as good performers (n = 9) and poor performers (n = 12), hip muscle strength (hip abduction, external rotation, and trunk side bridge) and onset timing of anterior (AGM) and posterior gluteus medius (PGM) electromyographic activity were compared. Results: Concurrency with the consensus panel was excellent to substantial for the 3 raters (agreement 87%-73%; κ = 0.800-0.600). Similarly, intrarater agreement was excellent to substantial (agreement 87%-73%; κ = 0.800-0.613). Participants rated as good performers had significantly earlier onset timing of AGM (mean difference, –152; 95% confidence interval [CI], –258 to –48 ms) and PGM (mean difference, –115; 95% CI, –227 to –3 ms) electromyographic activity than those who were rated as poor performers. The good performers also exhibited greater hip abduction torque (mean difference, 0.47; 95% CI, 0.10-0.83 N·m·Bw−1) and trunk side flexion force (mean difference, 1.08; 95% CI, 0.25-1.91 N·Bw−1). There was no difference in hip external rotation torque (P > .05) between the 2 groups. Conclusion: Targeted treatments, although considered ideal, rely on the capacity to identify subgroups of people with chronic anterior knee pain who might respond optimally to a given treatment component. Clinical assessment of performance on the single-leg squat task is a reliable tool that may be used to identify people with hip muscle dysfunction.

The Relationships Between Inter-recti Distance Measured by Ultrasound Imaging and Abdominal Muscle Function in Postpartum Women: A 6-Month Follow-up Study

A prospective longitudinal study. Diastasis recti abdominis (DRA) is defined as an increase in the inter-recti distance (IRD), or width of the linea alba. It is a common occurrence in women postpartum. Little information exists on the short- and long-term recovery of IRD and the relationship between changes in IRD and the functional performance of the abdominal muscles. To investigate the natural recovery of IRD and abdominal muscle strength and endurance in women between 7 weeks and 6 months postpartum, and to examine the relationship between IRD and abdominal muscle function. Forty postpartum (25-37 years of age) and 20 age-matched, nulliparous females participated. IRD was measured at 4 locations (upper and lower margin of the umbilical ring, and 2.5 cm above and below the umbilical ring) with a 7.5-MHz linear ultrasound transducer. Trunk flexion and rotation strength and endurance were measured with manual muscle testing and curl-ups. Evaluation was conducted at 4 to 8 weeks and 6 to 8 months after childbirth in postpartum women, and only once for the nulliparous female controls. During follow-up, the IRD at 2.5 cm above the umbilical ring and at the upper margin of the umbilical ring decreased (P = .013 and P = .002, respectively). The strength and static endurance of the abdominal muscles improved over time (P<.05). A negative correlation between IRD and abdominal muscle function at 7 weeks and 6 months postpartum was found (r = 0.34 to 0.51; P<.05, except for trunk flexion strength at 6 months postpartum [P = .064]). In addition, IRD changes between 7 weeks and 6 months postpartum were correlated with improvement in trunk flexion strength (Spearman rho = 0.38, P = .040). At 6 months after childbirth, postpartum women had greater mean ? SD IRDs at all 4 locations (from cranial to caudal: 1.80 ± 0.72, 2.13 ± 0.65, 1.81 ± 0.62, and 1.16 ± 0.58 cm) than those of nulliparous females (0.85 ± 0.26, 0.99 ± 0.31, 0.65 ± 0.23, and 0.43 ± 0.17 cm) (all P<.001). All abdominal strength and endurance measurements were less than those of nulliparous females (all P<.001). The IRD and abdominal muscle function of postpartum women improved but had not returned to normal values at 6 months after childbirth. Future research is essential to explore the need for intervention and, if needed, the effectiveness of specific intervention to reduce the size of IRD in postpartum women.

Low Back Pain And Lumbar Radiological Abnormalities In Collegiate Judo Players

A high incidence of low back pain (LBP) has been reported among many kinds of sports. In judo, the same tendency has also been confirmed. We reported at the 51st ACSM annual meeting that collegiate judo players with LBP showed lower trunk extensor and rotator strength. Lumbar radiological abnormalities (RA) have been also reported to have relationships with LBP. PURPOSE This study was to examine the incidences of LBP and RA in collegiate judo players. We especially focused on weight classes. METHODS Subjects were 82 male collegiate judo players. In this study, we classified judo players into three weight classes: the lightweight (−60, −66 kg, N=30), the middleweight (−73, −81 kg, N=30), and the heavyweight (−90, −100, +100 kg, N=22). The presence of LBP was evaluated using the questionnaire test developed by Osaka City University (the OCU test). Based on the OCU test score, we defined LBP as occurring when players graded more than one point. RA was examined by using x-ray and magnetic resonance imaging. The incidences of LBP and RA were compared between the three weight classes, using a chi-squared test for the statistical evaluation. Significance was accepted at the 5%level. RESULTS The incidence of LBP in the lightweight, middleweight and heavyweight classes were 36.7%, 33.3% and 36.4% respectively. The incidence of RA in the lightweight, middleweight and heavyweight classes were 66.7%, 90.0% and 90.9% respectively. The incidence of RA in the middleweight and heavyweight classes were significantly higher than the lightweight class (P <0.05). Furthermore, co-incidence of LBP and RA in the lightweight, middleweight and heavyweight classes were 54.5%, 100% and 87.5% respectively. Co-incidence of LBP and RA in the middleweight class was significantly higher than that in the lightweight class (P <0.05). CONCLUSIONS Not LBP but RA is related to weight classes in judo players. Moreover, greater co-incidence of LBP and RA is apparent in the middleweight and heavyweight classes. About one half of LBP in the lightweight class could be related to reasons other than RA.

An Isokinetic Profile of Trunk Rotation Strength in Elite Tennis Players

The changes in stroke production in the modern game of tennis have increased the demands on trunk rotation in elite tennis players. Unlike the shoulder, where unilateral strength adaptations have been identified, no study to date has objectively quantified side to side rotational trunk strength in elite tennis players. One hundred nine elite tennis players were tested using a Cybex isokinetic torso rotation unit at 60 and 120 degrees x s(-1) to measure left and right rotation while stabilized in a seated position. A repeated-measures ANOVA was used with post hoc dependent t-tests where main effect differences were identified to determine side to side rotational differences. No significant difference in trunk rotation strength was measured in the elite male players. Peak torque to body weight ratios averaged 63.7 and 57.5% for forehand rotation (left rotation in right-handed player) and 64.4 and 59.2% for backhand rotation at 60 and 120 degrees x s(-1), respectively. In females, slightly greater (P < 0.001) backhand rotation strength (right rotation in a right-handed player) was measured at both testing speeds with peak torque to body weight ratios ranging between 47.7 and 45.1% for left rotation and 50.8 and 48.3% for right rotation at 60 and 120 degrees x s(-1), respectively. Left rotation/right rotation ratios ranged from 95 to 98% for males and from 94 to 96% for females. Elite-level male tennis players have symmetric trunk rotation strength. Elite female tennis players have slightly greater backhand rotation strength (by 4-8%) than forehand rotation. Conditioning programs for elite tennis players should include exercises to facilitate and develop bilateral trunk rotation.