Source: Knee Surgery, Sports Traumatology, Arthroscopy. 3(2):121-4, 1995.
Authors: Koukoubis TD. Cooper LW. Glisson RR. Seaber AV. Feagin JA Jr.
Institution: Division of Orthopaedic Surgery, Duke University Medical Center, Durham, NC 27710, USA.

OBJECTIVES: Upper extremity muscle injuries from rock climbing are common. Knowledge of the activity of specific muscles during climbing may allow the development of training programs to reduce these injuries. 

METHODS: This study evaluated the electrical activity of the first interosseous (IN), brachioradialis (BR), flexor digitorum superficialis (FD), and biceps brachii (BB) muscles in seven climbers by integrated electromyography (IEMG) during finger-tip pull-ups. 

The climbers, with forearms pronated, performed three consecutive pull-ups. Each pull-up consisted of: (1) hanging using four fingers of each hand, (2) pull-up to maximum elbow flexion, (3) slow return to starting position. 

RESULTS: The IEMG during maximum voluntary contraction (MVC) was obtained for each muscle separately, and the IEMG was normalized to MVC. During hanging, FD showed the highest normalized IEMG (0.64 +/- 0.20). During pull-up, the highest IEMG was produced by FD (0.69 +/- 0.25) and BR (0.67 +/- 0.19), while BB showed only 0.33 +/- 0.12 and IN 0.09 +/- 0.06. During lowering, FD again had the highest IEMG (0.74 +/- 0.24), while the EMG from BR was decreased to 0.42 +/- 0.14 and BB to 0.15 +/- 0.15. BR and BB showed an abrupt peak in EMG during pull-up and lowering, as opposed to FD which remained constantly highly activated, which suggests that FD does not contribute to elbow flexion even though it crosses the elbow joint. 

CONCLUSIONS: The high activation of FD and BR may explain their elevated incidence of injury during climbing. Thus, a reduction in climbing-related muscle injuries may be achieved by a training program that emphasizes conditioning of the BR and FD muscles.