In current competitive swimming, the difference between finishing first or second, placing or not can be milliseconds. This is especially true for the shorter distances where the start has been estimated to contribute up to 30% of the total race in the 50m sprints (Fig. 1).
This can be observed in most races; perfect examples can be seen from the 2012 London Olympics. The men’s 100m Freestyle race saw America’s Nathan Adrian win with a time of 47.52s, Australia’s James Magnussen came an extraordinarily close second with a time of 47.53s. These close times can be seen again in the men’s 200m Freestyle, where Canadian Yannick Agnel won the race at 1.43.14, and although there is a significant time difference (in swimming timing terms) to second, at 1.44.93, both Korea’s Taehwan Park, and China’s Yang Sun achieved this time coming an equal second place.
This being the case, even the smallest portion of improvement through speed or distance covered, can substantially improve an athletes race time and success.
In this blog I will explore the dive start, investigate the biomechanical comparison of the three most used dive techniques, and endeavour to determine the most effective technique. You are able to navigate your way through this biomechanical comparison by using the sub-questions in the menu above, ‘Home’ will return you to this page.
The Grab Start:
The grab start if often taught first, being it can be most easily controlled by young swimmers and provides most balance and control on the blocks.
The grab start involves two feet together with toes curled over the edge of the block, the hands are placed either between or either side of the feet, with fingers curled around the edge of the block also.
Hips should be kept high, with head looking down to ensure this stature, and knees slightly bent.
Figure 2: Starting position
When diving using this technique, swimmers place their centre of gravity as far forward as possible, (see Figure 2, red circle) this enables the smallest amount of forward displacement of the centre of gravity for the body to effectively generate forward propulsion. Swimmers use their arms to stabilise and support their position, the arms are then thrown forward to create forward momentum, both legs drive powerfully and simultaneously from the block.
The Track Start:
The track start is often a copy-cat dive, where successful swimmers are seen through the media to use this technique and so it is taught to swimmers as the most successful dive technique, but is not always the case.
The track start involves the swimmers preferred leg forward, toes curled around the edge of the block as in the grab start. The difference being the other foot is placed slightly further back, as if starting a block start in track running (hence the name). Hands are placed either side of the front foot. As in the grab start, hips should be high, head facing down, and knees slightly bent.
Figure 3: Starting position
When diving using the track start swimmers are able to get a “double” push off from their legs. Where by they push with their back leg until fully extended, and then push with their preferred (front) leg, giving a second more powerful push. The swimmer uses their arms to stabilise their centre of gravity close to the front of the block, then uses the hands to pull against the blocks creating the opposite reaction force, propelling themselves forward. Once the centre of gravity has passed the front of the block, the back leg should have extended, and the front leg dominates force production.
The Rear-Weighted Start/ Slingshot Start:
This dive is identical to the track start, except for the swimmer pulls back on their arms, bringing their centre of gravity backwards, and placing tension on their arms and front leg.
Figure 4: Starting position.
The centre of gravity being further back in this start compared to the grab and track starts, results in a far longer block time. This disadvantage is offset by many factors. Firstly, the greater block time enables the swimmer to generate more impulse (a result of force x time) and therefore greater take off velocity. In addition, leaning back enables them to load the muscles in their arms and shoulders. This has been shown to enhance force production capability.