The purpose of this study was to examine whether repetitive muscle tasks in low weight load might influence the fatigue of forearm muscles, and to identify ergonomic risk factors of forearm muscle fatigue in these tasks. Sixteen healthy male volunteers performed eight wrist extensions in different frequency, weight and angle loads while being instructed to keep a dominant upper limb posture as constant as possible. Surface electromyograph (sEMG) was recorded from right extensors digitorium (ED), flexor carpi radialis (FCR), flexor carpi ulnaris (FCU) and extensor carpi ulnaris (ECU) during the task performance. Our results showed that mean power frequency (MPF) and median frequency (MF) values of ED, FCR and FCU were significantly lower (P<0.05) at high frequency load level than at low load level. However, MPF and MF values of ED were significantly lower (P<0.01) in higher load groups of frequency, angle and weight than in lower load groups. These results indicated that the fatigue of muscles varied in the same task, and the number-one risk factor of ECU, ED and FCR was angle load.
Cumulative Trauma Disorders/complications ; Cumulative Trauma Disorders/*physiopathology ; Electromyography ; Forearm/*physiology ; Muscle Fatigue/*physiology ; Muscle, Skeletal/*physiopathology ; Young Adult

INTRODUCTIONSports injuries in children and adolescent present a unique challenge to the physician. They are often seen for clinical conditions unique to their age group. This paper highlights the epidemiological aspect of sports-related overuse injuries in this age group.

MATERIALS AND METHODSThis retrospective study reviewed all the paediatric patients diagnosed with overuses injuries during a 5 years and 7 months period. The overuse injuries were anterior superior iliac spine avulsion fracture, Osgood-Schlatter disease, Sinding-Larson-Johansson disease, osteochondritis dissecan and Sever's disease. We reviewed the literature and attempted to give an overview for each condition and the anatomical differences that contributed to their occurrence in this age group.

RESULTSA total of 506 cases of the overuse injuries were seen during the study period. Seventy-three per cent were male patients. The knee joint was the commonest affected joint while the hip was the least affected joint. The mean age at diagnosis was younger in female compared to male for all conditions except in Sinding-Larson Johansson syndrome. Female was diagnosed at a mean age of 11.7 years while male at 10.8 years. Osgood-Schlatter disease was the commonest among the overuse injuries. There was no discernible racial predilection for these conditions except in the patients with anterior superior iliac spine avulsion.

CONCLUSIONSOveruse injuries are not uncommon in children and adolescent. An adequate understanding of the anatomy of the sports the children participated in as well as the anatomical differences between adult and children may assist the primary care providers better meet parents' and coaches' expectations.

Athletic Injuries ; classification ; epidemiology ; physiopathology ; Child ; Cumulative Trauma Disorders ; classification ; epidemiology ; physiopathology ; Female ; Humans ; Lower Extremity ; injuries ; Male ; Medical Audit ; Retrospective Studies ; Singapore ; epidemiology