3D Analysis in Swimming

Why is it important to consider factors other than SR and SL?

SR and SL are mostly descriptive and don’t provide much information on the quality of the movement. Other factors to consider are upper and lower extremity kinematics (velocity, displacement, ROM of segments), inter-cycle changes in body velocity and rotation of the body (body roll).

What velocity fluctuations linked to?

Vfluc linked to skill/efficiency e.g. faster swimmers expected to have less Vfluc than slower swimmers.

What type of research has been conducted on velocity fluctuations in swimming?

Previous research mostly in breaststroke or butterfly, often a single stroke cycle. Velocity calculated for a fixed point e.g. hips using 2D methods.

What has Vfluc research found?

Faster swimmers has lower Vfluc and higher Vmin than slower swimmers.

What are limitations in current Vfluc research?

A single stroke cycle is not representative of a swimmers full capability. Need to take into account all segments of human body 9CM variables) to measure velocity. Assuming symmetry is not best for human movement (even in symmetrical strokes) as differences in hand entry etc. occur. Need to consider the effect of breathing on Vfluc and if there are M-L and vertical changes but can only do this with 3D analysis.

What is body roll?

The rotation of the trunk around it’s longitudinal axis.

What are the functions of body roll?

BR facilitates breathing action, influences hand displacement and velocity, might assist in development of propulsive lift forces and might reduce risk of developing shoulder injuries.

How much body roll is needed?

There is not consensus in literature about this. Some say ‘good body roll not too much and not too little, intergrated properly with the rest of the stroke’ and others say ‘ as much body roll as you can while still maintaining a nice stroke rhythm’.

What type of research has been conducted on BR?

Simulation and 2D/3D experimental.

Provide an example of a simulated BR study.

Lee et al (2008) simulated 60s front crawl breathing and non-breathing trials on a swimming bench. The bench allowed rotation of the head, shoulders and hips but limitations include gravity of land not water, no resistance on land, rotation between shoulders and hips are different, and no information provided about attachment to bench.

What does 2D BR method look like?

Wood fin mounted to swimmers back and swimmers swim towards a poolside camera. BR measured for the whole trunk and is the angle between fin and vertical axis.

What are findings from 2D BR research?

BR affects hand velocity with contradicting results amongst breathing.

What are the reasons for variations in findings in 2D BR research?

Swimming level, gender and high SD for a given intensity.

What are limitations in 2D BR research?

Weight and tension of fin across trunk, fin affects ROM and resistance, movement between the fin and trunk, not in competition, fin around chest doesn’t show BR for shoulders or hips and fin sometimes goes underwater increasing resistance.

What does methods for 3D BR research look like?

BR calculated separately for shoulders and hips with the use of 2 camera during competition and tests.

What are the main findings of 3D BR research?

Shoulders seem to roll more than the hip (no statistical analysis), elite swimmers rolled their shoulders and hips towards the same direction but some sub-elite seemed to roll the shoulders and hips in opposite directions. Swimmers affected when test velocity increased from 1.3-1.6 m/s as shoulder roll decreased (no statistical analysis).

What are limitations to 3D BR rsearch?

Only 2 camera so view of markers might be lost (guessing) thus reducing accuracy, no mention of inclusion criteria 9what classifies elite and sub-elite), no statistical analysis, breathing not taken into account, total roll calculated only, not exploring potential bilateral asymmetries.

What are methodological issues in BR and Vfluc research and how did Psycharakis tackle them?

Inconsistent patterns, high intra subject SD so try get swimmers of national level with a more establish kinematic pattern. Breathing influences BR and Vfluc so need 2 separate studies: breathing and non-breathing trials and compare the differences. Previous studies reported total BR only so need to calculate BR for both sides and assess handedness to calculate roll of dominant and non-dominant sides. Previous studies calculated Vfluc for swimming direction only so calculate Vfluc for M-L and vertical direction. Vfluc only reported for fixed points on the body so calculated Vfluc for CM (19 anatomical markers) and compare with Vfluc of the hip. A large calibration frame is required to ensure at least one stroke cycle is captured. Calibrating space above and below water so used ‘legs’ for frame to stand on with half frame above and half below water. Digitising error so used repeated digitising by the same and different operators. Limited number of cameras requires guessing so use 6 cameras (4 under and 2 above water). Manual digitising is time consuming.

What are the intra-cycle Vfluc variables used by Psycharakis?

Velocity of CM compared with velocity of hip. Vmax, Vmin and Vfluc normalised as a % Vmean for each stroke cycle. Vfluc in all 3 directions.

What are the Vfluc findings from Psycharakis?

Hip V very different to V of CM. Use of hip overestimates Vmax and underestimates Vmin. Use of hip overestimates Vfluc overall. Vmean, Vmax and Vmin decreased during 200m swim. Faster swimmers had a higher Vmax and Vmin however when normalised Vmax and Vmin did not change during 200m. Velocity drops each segment (50m). High Vfluc in vertical and M-L directions but no changes in Vfluc during 200m.

How was BR calculated by Psycharakis?

Separate calculation of shoulder roll (SR) and hip roll (HR). SR and HR for dominant and non-dominant sides. Temporal characteristics explored.

What are the changes of SR and HR with fatigue in Psycharakis?

Shoulder roll about twice as much as the hips. HR increased during 200m, SR consistent throughout. Shoulders and hips reached left and right peaks at the same time.

What asymmetries in BR did Psycharakis find?

SR asymmetrical (higher in non-dominant side). Faster swimmers had lower SR when swimming at sub-max V suggesting lower trunk twist and lower resistive forces at position of peak roll.

What was the effect of breathing, pace and specialisation found by Psycharakis?

SR and HR increased at breathing side only; no changes in total roll. No temporal changes in roll when breathing. There was no differences between sprint and distance swimmers when tested at sprint or distance pace.