F-2-16-04
THREE-DIMENSIONAL MOTION ANALYSIS OF UPPER LIMB MOVEMENT IN THE BOWING ARM OF STRING-PLAYING MUSICIANS
Lynne Turner-Stokes and Keith Reid
(Regional Rehabilitation Unit, Northwick Park Hospital, UK)
Three-dimensional movement analysis of the bowing arm in string playing musicians may prove helpful in identifying movement patterns which could exacerbate repetitive strain injuries. However, the technique has only recently become available. The aim of this study was to develop a protocol and obtain normative data.
Method: The MacReflex system was used to analyse bowing arm movement. In this system, two cameras record the 3-D co-ordinates of retroreflective markers at 50Hz via two on-line video processors connected to a computer. The data is processed using the Wingz software to give information on a range of parameters including angle, velocity and acceleration, from which relative movement at different joints can be derived. After a pilot study to determine optimum placement of markers and a feasible programme of bowing styles, a normative dataset was collected in a cohort of 22 young asymptomatic string players. Range of joint movements in the shoulder, elbow and wrist were determined and also the relative movement of joints in different bowing styles, on different strings across different instruments - violin, viola, cello and double-bass.
Results: In full bow legato strokes, the range of elbow movement cellists (mean 33°) was approximately half that in violinists (mean 71°) but was similar across all four strings. Shoulder range increased from 16° on the bottom string to 30° on the top in cellists, while decreasing from 24° to 16° in violinists. This difference results from the differently orientated playing position of the cello and violin.
Conclusions: The system proved reliable in detecting consistent differences between instruments and bowing patterns, and yet is sensitive to differences in style between individuals. It has the potential to be useful in identifying factors which contribute to musculoskeletal syndromes in string players.
F-2-16-05
THREE-DIMENSIONAL MOTION ANALYSIS OF CUTTING ACTION WITH A KITCHEN KNIFE
Akinobu Nemoto, Manabu Nonogki, Yasunori Sakamoto, Kaazuya Mizuochi and Norihiko Ando
(Yokohama City University, Yokohama, Japan)
The purpose of this study was to analyze the stress exerted on a wrist joint due to a cutting motion. The subjects, 10 healthy volunteers, were instructed to cut a piece of plastic eraser (3*3*6mm) on a Kistler force plate (Model 9286) that was placed on a solid table. Kinetic data were obtained from the force plate at 60Hz. We attached reflective markers to the shoulder (acromion), elbow (olecranon), wrist (styloid process of the ulna and styloid process of the radius), the second metacarpophalangeal joint, the 5th metacarpophalangeal joints, and 3 points on the back of a knife blade (top, center and the base). Kinematic data were obtained from 4 video cameras at 60Hz and an Oxford Metrics VICON 370 system, using direct linear transformation. Velocities and accelerations were calculated after low-pass filtering and differentiation. Net torque was calculated, based on a dynamic, three-dimensional link segment model. Each subject cut the eraser using 3 different parts of the blade (the point, center, and base). The results showed that there were no significant differences in absolute forces to cut the piece of eraser but less torque was read at the wrist joint when the piece was cut by using the base of the kitchen knife than by using its center or the tip of the blade. Until the present, we have instructed patients with rheumatoid arthritis to minimize joint stress based on empirical knowledge. The method that we described here makes it possible to express joint stress numerically. Based on objective findings, we are now able to give patients more convincing instructions to preserve their joint functions.
