Relationship between upper limb physical performance tests and muscle strength of scapular, shoulder and spine stabilizers: A cross-sectional study

Postural control and shoulder rotators isokinetic strength in squash players with and without idiopathic scoliosis

Idiopathic scoliosis is a postural deformity of the spine that not only changes the shape of the spine but may also alter postural control and muscle strength. Although this deformity is more common in some sports, it is not known whether the scoliosis athlete's balance and strength are altered. Balance and strength are essential to perform complex technical movements and prevent injuries. This cross-sectional study compared postural control and isokinetic strength of shoulder rotator muscles in squash players with and without idiopathic scoliosis and the control group. We report a higher mediolateral stability index in the frontal plane in scoliosis athletes and this may be associated with increased variability in postural control in the frontal plane. Additionally, the peak torque of the shoulder rotators was not different between the groups. While the relationship between function and posture is complex, these results provide information for preventive health care interventions in scoliosis athletes.

Sex differences in strength at the shoulder: a systematic review

Background

Understanding differential strength capability between sexes is critical in ergonomics and task design. Variations in study designs and outcome measures generates challenges in establishing workplace guidelines for strength requirements to minimize upper extremity risk for workers. The purpose of this systematic review was to collate and summarize sex differences in strength at the shoulder across movement directions and contraction types.

Methods

A total of 3,294 articles were screened from four databases (Embase, Medline, SCOPUS, and Web of Science). Eligibility criteria included observational studies, direct measurement of muscular joint, and healthy adult participants (18-65 years old). Strength outcome measures were normalized to percentages of male outputs to allow comparisons across articles.

Results

A total of 63 studies were included within the final review. Majority of articles observed increased strength in males; the gap between male-female strength was greater in flexion and internal/external rotation, with females generating ~30% of male strength; scaption strength ratios were most consistent of the movement groups, with females generating 55-62% of male strength.

Conclusion

Sex strength differences should be considered as an important factor for workplace task design as women are more at risk for occupational-related injuries than men in equivalent strength requirements. Differences in strength were not synonymous across motions; females demonstrated increased disparity relative to male strength in horizontal flexion/extension, forward flexion and internal/external rotation. Some movements had an extremely limited pool of available studies for examination which identified critical research gaps within the literature. Collating and quantifying strength differences is critical for effective workstation design with a range of users to mitigate potential overexertion risk and musculoskeletal injury.

Relationship between Upper Limb Functional Assessment and Clinical Tests of Shoulder Mobility and Posture in Individuals Participating in Recreational Strength Training

BACKGROUND

The upper limb is crucial for functioning in everyday life, thus comprehensive assessment is crucial for physically active people to monitor the effect of exercise and prevent injuries. The aim of this study was to analyse the relationship between upper limb function, shoulder mobility, and posture in individuals who participate in recreational strength training.

METHODS

Thirty-four subjects who engaged in strength training of the upper limbs were divided into two groups: Group 1 (exercise < 3 years) and Group 2 (exercise ≥ 3 years). Lateral scapular slide tests, head and clavicle posture evaluations, and shoulder mobility and closed kinetic chain tests were performed.

RESULTS

Group 1 had a greater flexion deficit in both shoulders than Group 2. There was greater external rotation in the non-dominant shoulder and a greater score of the closed kinetic chain test in Group 2 compared to Group 1. There were no statistically significant differences between groups regarding scapula, clavicle, and head posture. The closed kinetic chain test was correlated with a scapula position and symmetry in shoulder flexion in Group 2.

CONCLUSIONS

Long-term strength training of the upper limbs can be recommended to improve functional abilities in the closed kinetic chain, increase shoulder mobility, and reduce asymmetry.

Role of active joint position sense on the upper extremity functional performance tests in college volleyball players

Background

It has been well established that proprioception plays a decisive role in shoulder stability and sport performance. Notwithstanding, there is a lack of clear association between active joint position sense (AJPS) and the performance of upper-extremity functional performance tests. The aim of this study was to determine whether the AJPS of the shoulder complex is associated with the performance of college volleyball players with the following functional tests: Y-Balance Test-Upper Quarter (YBT-UQ), Closed Kinetic Chain Upper-Extremity Stability Test (CKCUEST), and Seated Medicine Ball Throw (SMBT). The secondary aim was to investigate whether the magnitude of the proprioception error through the AJPS had the ability to act as a predictor for functional test scores.

Methods

Cross-sectional study with a convenience sampling. Healthy college volleyball players (≥12 h of training/week), 30 males and 22 females, between 18 and 26 years of age were included. AJPS of the shoulder (90° of flexion (90°Flex), 90° of internal rotation at 90° of abduction (90°IR/ABD), 90° of external rotation at 90° of abduction (90°ER/ABD)) and three upper-extremity functional performance tests (YBT-UQ, CKCUEST and SMBT) were assessed. A Pearson's test and a stepwise multiple linear regression analysis were used to determine possible associations and relationships between outcome measures, respectively.

Results

The analysis revealed that AJPS at 90°IR/ABD and 90°ER/ABD were the only proprioceptive variables with an association to the YBT-UQ and SMBT. Despite these relationships, only the AJPS at 90°IR/ABD was associated with the performance of the YBT-UQ in; superolateral direction (β = -0.7; 95% CI [-1.3 to 0.1]; p = 0.025); inferolateral direction (β = -1.5; 95% CI [-2.1 to -0.8]; p = 0.001); and composite score (β = -0.8; 95% CI [-1.3 to -0.3]; p = 0.002). From these, AJPS at 90°IR/ABD mainly explained the variability of YBT-UQ (inferolateral direction) performance (R² = 0.32; %R² = 0.32). Our findings allow for a possible expanded role for proprioception as a contributing factor in upper limb motor control during functional movements. Further research is required to explore and distinguish the associations between proprioception, motor control and sport performance involving the upper limbs.