Wrist stabilisation and forearm muscle coactivation during freestyle swimming.

The aim of this study was to evaluate the stabilisation of the wrist joint and the ad hoc wrist muscles activations during the two principal phases of the freestyle stroke. Seven male international swimmers performed a maximal semi-tethered power test. A swimming ergometer fixed on the start area of the pool was used to collect maximal power. The electromyography signal (EMG) of the right flexor carpi ulnaris (FCU) and extensor carpi ulnaris (ECU) was recorded with surface electrodes and processed using the integrated EMG (IEMG). Frontal and sagittal video views were digitised frame by frame to determine the wrist angle in the sagittal plane and the principal phases of the stroke (insweep, outsweep). Important stabilisation of the wrist and high antagonist muscle activity were observed during the insweep phase due to the great mechanical constraints. In outsweep, less stabilisation and lower antagonist activities were noted. Factors affecting coactivations in elementary movements, e.g. intensity and instability of the load, accuracy and economy of the movement were confirmed in complex aquatic movement.

Relative contribution of arms and legs in humans to propulsion in 25-m sprint front-crawl swimming.

Eight male subjects were asked to swim 25 m at maximal velocity while the use of the arm(s) and legs was alternately restricted. Four situations were examined using one arm (1A), two arms (2A), one arm and two legs (1A2L) and both arms and legs (2A2L, normal swim) for propulsion. A significant mean increase of 10% on maximal velocity was obtained in 1A2L and 2A2L compared to 1A and 2A. A non-significant 4% effect was obtained in 1A. This study focused on the actual contribution of leg kick in the 10% gain in maximal velocity. It was clear that the underwater trajectory of the wrist was modified by the action of the legs (most comparisons P < 0.001). Therefore it was thought that the legs enhanced the generated propulsive force by improving the propulsive action of the arm. The arm action was quantified by selecting typical phases from the filmed trajectory of the wrist, namely forward (F), downwards (D) and backwards (B). Although there was a tendency for individual changes in kinematic parameters (F, D and B) to occur with individual changes in velocity when 2A was compared to 2A2L, no relationship was found between the relative changes in F, D and B and relative changes in velocity. This was illustrated by describing the responses of three individuals who could represent three patterns of contribution by legs and arms to propulsion in high speed swimming.

Hydrodynamics optimization in butterfly swimming: position, drag coefficient and performance.

A kinematic study allowed to define the three most propulsive positions during a butterfly swimming cycle, which were: the end of the external sweep, the end of the internal sweep and the end of thrust. These instantaneous positions were different for the ex-world champion Pankratov when compared to another swimmer. Using manikins and a drag-measuring device, we showed that the end of the internal sweep induced the highest drag values and that Pankratov may reduce energy expenditure by taking up a particular position during the end of the swimming cycle. These results point out the relations between swimming movements, passive drag and swimmers' performance.

Muscular activations during repetitions of sculling movements up to exhaustion in swimming.

The purpose of this study was to examine the influence of the repetition of sculling movements of the upper limb on muscular electrical activities during an exhaustive test in front crawl. Six upper limb muscles activities of nine swimmers were recorded, with telemetric EMG data acquisition system using active surface electrodes, during a 4 x 100 m front crawl test conducted to exhaustion. The pattern of the movement was analysed from views obtained by recordings of two underwater cameras. Four phases in the stroke were identified from the hand coordinates in the frontal plane (down-sweep, insweep, outsweep and recovery). Raw EMG were rectified, integrated (IEMG) and normalized for each subject and for each muscle with respect to the highest IEMG obtained during the strokes and the phases. Results indicated that the repetition of the stroke up to exhaustion was not associated with an increase in IEMG for the total stroke and its phases excepted for the most activated muscle. The different sculling movements appeared to be clearly identify by the EMG approach whatever the trial. The contribution of the different muscles remained the same through the different repetitions up to exhaustion. The larger muscular recruitments were obtained during the insweep phase when important antagonist activities were observed. It would be interesting to observe the EMG in a next 100 m repetition when the swimmer could not sustain the same velocity.

The frontcrawl downsweep: shoulder protection and/or performance inhibition.

EMG of 6 shoulder and arm muscles was measured in nine good frontcrawl swimmers using active electrodes and a telemetric EMG data acquisition system. The raw EMG was low pass filtered, rectified and the integrated values were used as a measure of muscular intensity. The selection of muscles combined 2 mono-articular and 2 bi-articular shoulder muscles and 2 muscular primarily acting on elbow & wrist. Kinematic analysis allowed for a detailed time and movement pattern fractionation and the muscle activity within these phases was analysed for 4 x 100 m at maximum effort up to exhaustion. The combination of time distribution and muscular activity suggested that the downsweep is the longest in time but with the lowest intensity of all 4 transient phases of the cyclic arm movement. This is assumed to be effective for decreasing the load of the shoulder joint. However, it could also be considered that if the insweep with its higher muscular participation could start earlier in the pull phase while shortening the downsweep. The higher, but more constant loading of the shoulder might improve performance.

Cocontraction in the elbow and shoulder muscles during rapid cyclic movements in an aquatic environment.

The purpose of this study was to document the cocontraction patterns of the combined wrist-elbow-shoulder joint muscles during maximal-effort swimming. The subjects, nine high-performance athletes, swam 4 x 100 m at maximal effort with a 45 s rest after each 100 m run. Electromyographic (EMG) recording of six muscles was performed with surface electrodes and telemetry. The quality of the arm movement was verified with two video cameras and the movement was divided into four phases: the initial press, the inward scull, the outward scull and the air recovery. Eccentric work and antagonist co-activation of the arm extensors varied within the motion cycle but were mostly present during the inward scull; i.e. it is assumed that coactivation is transient movement and is phase-dependent despite the rapidity of the movement. These data suggest that both eccentric work and cocontractions are important features of rapid cyclic repetitive movement with the m. biceps and the m. brachioradialis as prime movers.

Influences of sex and level of performance on freestyle stroke: an electromyography and kinematic study.

Surface Electromyography (EMG) of the upper arm was performed on 50 subjects (30 males and 20 females). The following six muscles were studied: M. flexor carpi ulnaris, M. brachioradialis, M. biceps brachii, M. triceps brachii and two parts of the M. deltoidus (anterior and medialis). A cinematographical analysis was synchronized with the EMG's recorded during swims at maximal speed. The kinematics data were: hip displacement, stroke rate and five stroke phases measured from the arm-trunk angles. EMG measurements were normalized for each subject and analysed using the statistical method of principal component analysis. The best swimmers, at the same relative effort, had a greater hip displacement, lower electrical muscular activity and more selective recruitment, indicating greater efficiency. The role of each muscle during the different phases was in agreement with previous investigations (2, 11, 13, 14, 19). The swimmer's technique, particularly the position of the upper arm during the push phase, influenced these results. Time parameters of the stroke were not significantly different for the various swimmer's levels. The conclusions were similar, for the females, however, with a worse displacement of the hip.