Reciprocal strength ratio in shoulder abduction/adduction in sports and daily living

Purpose: Functionally, the shoulder is considered a ball joint, whereby hig h mobility is attended by low stability. Therefore, muscular balance is dec isive for stability. Altered strength ratios are frequently described as "m uscular dysbalances" and considered one of the causes of shoulder pathologi es, whereby objective quantification is difficult. Methods: In order to qua ntify physiological muscle balance, the strength ratio of shoulder abductio n/adduction (AB/AD) was determined in 166 untrained men (UM) concentrically at 60 degrees .s(-1) (LIDO-Active). The influence on this norm of one-side d (25 high-performance (TPH), 18 leisure tennis players (TPL)) and two-side d athletic exercise (32 gymnasts (GY)), altered daily exercise (11 parapleg ics with paralysis time < 4 months (PP), 11 paraplegics with paralysis time > 2 yr (PU)), and a combination of altered daily exercise and athletic act ivity (16 trained paraplegics (PT)) was examined (ANOVA, alpha = 0.05). Res ults: Determination of the AB/AD quotient in UM was 0.82. Shoulder stress i n sports led to a decrease in quotients compared with UM because of a relat ively increased torque in AD (P < 0.01). At the beginning of a paraplegia, the quotient of AB/AD is elevated (P < 0.05). This altered ratio decreases with duration of paralysis (PU) and athletic activity (PT). Conclusion: Wit h increased shoulder stress, the altered strength ratios reflect specific r equirements of the performance attained. However, the importance of muscula r dysbalances for the onset of shoulder complaints must be considered more important than their influence on athletic performance capacity.