The purpose of this study was to present a method of determining the contributions made by rotations of the trunk and upper extremity to hand velocity during the front crawl pull, and to illustrate this with an example. Six male swimmers performed front crawl trials at their middle distance pace (1.52 ± 0.12 m.s−1). Their underwater arm stroke was recorded from the front and side using video cameras suspended over periscope systems. Recordings were digitized at 50 Hz and the 3-D coordinates of the upper extremity were obtained using a DLT algorithm. Shoulder kinematics (flexion/extension, transverse abduction/adduction, internal/external rotation) and elbow kinematics (flexion/extension) were then calculated. Trunk roll kinematics were obtained by digitizing above-water video recordings of a fin attached to each swimmer’s back. The contribution of each body segment rotation to hand velocity was computed using |ɷ × r| cos ϕ, where ɷ was the segment’s angular velocity, r was the position vector of the hand from the segment’s axis of rotation, and ϕ was the angle between hand velocity v hand/pool and v (where v = ɷ × r). Analysis revealed that shoulder extension was the joint motion primarily responsible for producing hand velocity during the insweep (relative contribution: min 66% to max 118%). This was due to the angular velocities and hand-to-joint axis distances for shoulder extension being greater than those of the other joint motions analyzed. The other rotations at the shoulder also contributed to hand velocity during the insweep, but to a lesser extent (transverse adduction: 13% to 49%; internal rotation: −1% to +40%). On average, elbow flexion accounted for 25% of the hand velocity in the middle of the insweep. Trunk roll did not make a positive contribution to hand velocity during the insweep phase (–3% to –48%), contradicting the findings of previous studies.
Carl Payton, Vasilios Baltzopoulos and Roger Bartlett
Carl J. Payton, James G. Hay and David R. Mullineaux
The aim of this study was to predict the effect of body roll on hand speed and hand path during the pull phase in front crawl swimming. An earlier three-segment model (Hay, Liu, & Andrews, 1993) was developed to enable the hand to move out of the plane through the shoulder parallel to the sagittal plane of the rotating trunk. Elbow flexion, shoulder abduction, and body roll angular velocities were modeled as sine or cosine functions. For a given elbow flexion, an increase in maximum body roll from 45° to 60° produced a marked increase in medial hand motion. For a given body roll, an increase in maximum elbow flexion from 60° to 90° increased medial hand motion and reduced downward hand motion. An increase in body roll increased hand speed in the plane perpendicular to the swimming direction, thus increasing the potential of the hand to develop propulsive lift forces.
Conor D. Osborough, Carl J. Payton and Daniel J. Daly
The purpose of this study was to determine the relationships between swimming speed (SS), stroke length (SL), and stroke frequency (SF) for competitive single-arm amputee front crawl swimmers and assess their relationships with anthropometric characteristics. Thirteen highly trained swimmers (3 male, 10 female) were filmed underwater from a lateral view during seven increasingly faster 25-m front crawl trials. Increases in SS (above 75% of maximum SS) were achieved by a 5% increase in SF, which coincided with a 2% decrease in SL. At SSmax, interswimmer correlations showed that SF was significantly related to SS (r = .72; p < .01) whereas SL was not. Moderate but nonsignificant correlations suggested that faster swimmers did not necessarily use longer and slower strokes to swim at a common submaximal speed when compared with their slower counterparts. No correlations existed between SL and any anthropometric characteristics. Biacromial breadth, shoulder girth, and upper-arm length all significantly correlated with the SF used at SSmax. These findings imply that as a consequence of being deprived of an important propelling limb, at fast swimming speeds SF is more important than SL in influencing the performance outcome of these single-arm amputee swimmers.