Comparison of wrist range of motion and muscle strength in assembly workers with and without lateral epicondylitis.

BACKGROUND: Lateral epicondylitis (LE), also called tennis elbow, is a common musculoskeletal disorder that causes pain in the elbow area and is highly prevalent in assembly workers who repeatedly move their wrists. OBJECTIVE: The purpose of this study was to compare the wrist ROM and muscle strength of assembly workers with and without LE. METHODS: Forty-five male assembly line workers (23 with LE) participated in the study. Participants had their wrist range of motion (flexion, extension, ulnar deviation, and radial deviation) and strength (wrist flexors, extensors, and hand grip) measured using Smart KEMA sensors. RESULTS: Workers with LE showed significantly reduced wrist extension and radial deviation ROM compared to workers without LE, with no significant differences in wrist flexion and ulnar deviation ROM between groups. Workers with LE had significantly lower wrist extensor strength compared to workers without LE, and there was no significant difference in wrist flexor and grip strength between the two groups. CONCLUSIONS: For workers with LE, the difference in wrist ROM and muscle strength will be useful for planning intervention and evaluating treatment outcomes for assembly workers with LE.

Comparison of acromiohumeral distance and glenohumeral internal rotation angle between the empty can test and modified empty can test: "thumb pointing down" versus "elbow pointing laterally".

BACKGROUND: During the empty can test, the direction of the thumb (downward) has been widely used as an instruction for producing glenohumeral internal rotation. However, the combination of forearm pronation and thumb motion as a compensatory movement could contribute to the lack of glenohumeral internal rotation during the empty can test. This study aimed to compare the glenohumeral internal rotation angle between the conventional empty can (with thumb direction) and modified empty can tests (with elbow direction), as well as the acromiohumeral distance between the full can, conventional empty can, and modified empty can tests. METHODS: In this laboratory study, we measured the glenohumeral internal rotation angle using a motion sensor and the acromiohumeral distance using ultrasonography during the following tests: full can test (thumb pointing up), conventional empty can test (thumb pointing down), and modified empty can test (elbow pointing laterally) in 20 healthy subjects. RESULTS: Compared with the conventional empty can test, the glenohumeral internal rotation angle was significantly greater during the modified empty can test (p < 0.05). Furthermore, the acromiohumeral distance measured in the modified empty can test was significantly less than that in the full can test (p < 0.001) and conventional empty can test (p < 0.001). However, there was no difference in the acromiohumeral distance between the full can test and the conventional empty can test (p > 0.017). CONCLUSIONS: During the empty can test, the instructions should be given to patients based on the elbow direction (elbow pointing laterally). The modified empty can test can produce full glenohumeral internal rotation, compared with instructions based on the thumb direction (thumb pointing down). Consequently, the modified empty can test can produce a more decreased subacromial space.

Differences in neck muscle activity according to lying positions using a smartphone.

BACKGROUND: Due to the extended use of smartphones, people spend a lot of time on these devices while lying down. OBJECTIVE: The purpose of the present study was to compare the differences in neck muscle activity of participants while they watched videos on a smartphone in four different lying positions (supine (SUP), prone on elbows (PE), side lying (SIDE), and 45∘ head turn while side lying (45-SIDE)). METHODS: Twenty-three healthy volunteers (22.4 ± 1.7 years) were enrolled in this study. We assessed the activities of their right and left sternocleidomastoid (SCM), anterior scalene, cervical erector spinae (CES), and upper trapezius (UT) muscles while they watched videos on a smartphone in four different lying positions. RESULTS: The right and left SCM and CES had significantly different muscle activities depending on the lying positions. The SCM activity had a significantly greater asymmetry in the 45-SIDE position, while the CES activity had a significantly greater asymmetry in the SIDE and 45-SIDE positions. Moreover, the UT activity had a significantly greater asymmetry in the SUP, PE, and SIDE positions. CONCLUSIONS: Neck muscle activity and asymmetry were the lowest in the SUP position relative to the other positions. Therefore, lying down in the SUP position may minimize neck muscle activation while using a smartphone.