PLEASE NOTE THAT THIS ARTICLE WAS WIRTTEN TO IDENTIFY THE DFFERENCE BETWEEN AN ELITE AND DEVELOPING ATHLETE’S START. THE ARTICLE TRIES TO IDENTIFY THE PERFORMANCE LIMITING FACTORS OF THE 100M START. THE FORMER WORLD RECORD HOLDER IS USED AS AN IDEAL OR A BENCH MARK TO SHOW AN EFFICIENT EXIT FROM THE BLOCKS.

The Start Analysis of a Developing Sprinter

The start of the 100m is far more crucial to the event than realised by many. The start consists of the reaction time, block clearance and the first and second stride of the 100m. To perform an exemplary start, an athlete must have the correct technique and angles, as well as maximal and explosive strength of the quadriceps, gluteus maximus, calf muscles and strong erector spinae.

In this article we will use photo sequences to analyse start technique.

The sequence shows a developing athlete and Asafa Powell 100m world record holder. Their starts are analysed to see where improvements can be made for Elijah Winn, a developing British athlete, Poewll is used as the bench mark. A Casio Exilim camera, capable of recording at 1000 frames/sec was used to capture footage; but filming was done at a setting of 300 frames per second. Video of the world record holder was acquired from the You Tube. The footage was downloaded and sequenced using Quintic sports analysis software. The original video was filmed at 1000 frames per second. Only the block clearance and first stride have been analyzed

The objective of the sprint start

1/ To acquire a balanced position in the blocks

2/ To obtain a body position where the COG is high and slightly forward of the front foot.
3/ To apply force through extension of the ankle, knee, and hip joints the centre of the trunk and head

4/ To apply force through an angle close to 45 degrees, (stronger athletes can achieve more acute angles of exit).

5/ To achieve an optimum knee angle for front and rear legs respectively. The recommended front block angle range is 90-100 degrees. The back block angle range is 120-130 degrees.

6/ Front block- The higher the force applied to the front block, the shorter the reaction time and the better the quality of the first step.

The time components of the start

Reaction time can vary a lot between 0.1-0.18 sec on average.

Experience decreases reaction time. According to Ozolin, the following time fractions are accorded to each section of the sprint start. Signal from the gun-0.00 sec. Reaction time-0.14 sec Hands leaving the track 0.15 sec Leaving the rear block 0.25 sec Leaving the front block 0.38 sec This accounts for 3-4% of the 100m running time or 0.3-0.4 sec.

The centre of gravity (COG) the (point where the body is balanced), is about 20-30cm from the start line. The height of the centre of gravity represents 32% of the athlete’s height. In the set position the COG is about 0.5-0.6m above the track level The body centre of gravity must be located behind the ground contact point of the foot.

The first two strides after block clearance (when both feet have left the blocks) is followed by a minimal flight phase (the shorter the better).

After this very short flight phase, the first contact is made. This first stride is approximately 1.1m long. The subsequent second phase is also about the same length. Contrary to commonly held opinion, these first two strides SHOULD NOT BE LENGTHENED.
The technical instruction given to athletes to lengthen the first stride by bring the “knee to chest” is technically and biomechanically incorrect. According to research by Dr Ralph Mann and USATF, elite sprinters generate over 50% of their final maximal speed after the first two strides.

In sprinting, air time dictates stride length and the combination of ground and air time determines stride rate/frequency.

The short stride length of the first two strides according to Mann is typical of the elite sprinter. They limit the flight time to a minimum whilst increasing contact time.
The contact time of the first step equates to about 77% of the first step. The second step contact time is equal to 65-70% of the second stride.

By limiting flight time they can spend more time on the ground to generate very large amounts of explosive strength to accelerate the body.

NOTE: EXECUTING AN OVERLY LONG FIRST STRIDE CAUSES NEGATIVE REACTION ON CONTACT WITH THE GROUND. THE COG AND GROUND REACTION LINE WILL BE IN THE WRONG PLACE. BRAKING WILL OCCUR.

Technical Pointers of the Sprint Start

Before looking at the sequence of photos; it is important to set out the features of a good start. Regardless of the body type, it seems that the “technical pointers” are the same.

The elite sprinters set their blocks in a similar fashion.

Back block is set 2/3 of distance of front block from start line.

Angle behind knee of front leg is 90-100 degrees.

Angle behind knee of back leg is 120-130 degrees.

A low block face angle guarantees the athlete a high horizontal start velocity.

After gun fire, the head travels forwards arms leave the ground first then legs drive against the blocks.

Lead arm is shortened and brought forwards and to the side.

Back arm is bent at elbow and is driven backwards and upwards.

A two leg drive is initiated.

The back is parallel with the ground as the two leg drive is completed.

Two leg drive ends with a low carriage of the rear leg forwards, with minimal flight phase.

The first step contact follows after a short flight phase, where both legs are off the ground.
The rear leg after touchdown of the first step is carried very low with the foot of the rear leg shuffling past the front shin bone.

The second step touchdown follows the take off from the first leg which is fully extended at the knee, ankle and hip joint.

At this point the lean at the waist is less pronounced, but ground reaction forces pass behind the knee.

The head is kept in a position that leads the torso and the eyes look forwards and downwards.

The second step take off completes the start. At end of the second stride, an elite sprinter would have generated over 50% of their maximum velocity. A 12 m/s sprinter would have attained a speed of 7 m/s at this point.

Photo 1-6, frames 273, 436, 473, 1824, 1930 and 1935

The former world record holder assumes a start position which can be characterised as a medium start. The rear knee angle is set at 130 and the front knee angle corresponds to an angle of 84 degrees.

The centre of gravity (green circle) of the former WR holder is positioned above the knee in the set position. The hands are set at 90 degrees to the ground. Hips are held higher than the shoulders’, this raises the centre of gravity. The COG is directly over the front knee, the ideal would be slightly ahead of the front knee.
Photo 4, frame 1824. The developing sprinter also adopts a set position which is close to a medium start.

The rear knee angle is very obtuse at 155 degrees, this falls well outside the recommended angle range. This position means that the quadriceps and calf muscles and Achilles tendon will experience less of a pre-stretch, as a result; the gluteus muscle and lower back muscle (erector spinae) will have to do more work. The front knee angle is set at 104 degrees, though out of the range, this is not much of a problem as the rear knee angle position.

The centre of gravity for the developing athlete is set slightly further to the start line for the developing athlete. This is the consequence of the hands being set at an angle of 64 degrees to the ground.
The head of the world record holder moves forwards, this is followed by the hands breaking contact with the surface of the track. The centre of gravity has moved ahead of the front knee towards the start line. The back, front and hip angles have extended (opened). The COG has not risen vertically yet. Photo 5-6, frame 1930-1935. As a result of less than optimal knee angles in the set position, the developing sprinter seems to sink lower, closing the angles of each knee and dropping the COG downwards and forwards. It seems that the body compensates by assuming a more flexed position in the front knee angle during push-off against the blocks. There is curvature in the back of the developing athlete in frame 436; this will lead to the lower back muscles providing less assistance to the gluteus and quadriceps during the drive from blocks. As the athlete pushes against the blocks, the front knee assumes a more flexed position decreasing from 104 to 94 degrees. The rear knee extends further from 155-166 degrees.

Photo 1-3, frames 532, 580, 619.

The hands have broken free from the surface of the track. The head is held in a position where the eyes are looking down and the top of the head is pointing forwards. The back is flat with no curvature. The centre of gravity is kept ahead of the front knee. Knee angles have extended. In frames 580 and 619 the back is parallel with the ground. There is a decrease in the back knee angle as the foot begins to leave the back block. The right arm of the world record holder has travelled backwards. The elbow has of the right arm begins to extend. The left arm begins to move upwards with the elbow flexing (closing towards the body). The knee angles (frame 1940) of the developing athlete, suggests that the body has already been projected further forwards than the world record holder, at the same point when executing the start. The foot of the developing athlete begins to break away from the surface of the back block. This suggests that a less than efficient and prolonged drive from the blocks is taking place. The centre of gravity has been projected forwards towards the start line (green circle). In comparison to the world record holder, the back never reaches a position where it is fully parallel with the ground plane. A glaring difference between the world record holder and the developing athlete in the frames is the lack of extension in the front knee of the developing athlete. The back foot breaks contact prematurely from the blocks in frame 1953, but in all the frames of the developing athlete; the knee angle hovers around 100 degrees suggesting a lack of the necessary strength needed to project the body forwards. This is a major flaw because the impulse generated against the front leg has been shown to be linked to a greater speed reached at 10, 20 and 30m in research.

Photo 1-3, frames 704, 778, 879

Photo 1-3, frames 953, 989, 1085

The former world record holder has a peculiar exit technique. As his foot leaves the front block, it drags across the floor. This is peculiar to him, but can be explained by his need to limit the flight phase of the initial and second stride.

Photo 1-6 frames, 2022, 2024 and 2042
In this sequence, the first stride of the developmental athlete is analysed. The yellow dashed line in the sequence shows the projection of the ground reaction force on contact with the ground. The orange dashed line shows the distance and location of the centre of gravity in relation to the front knee, foot and the ground. At contact the ground reaction force line should pass behind the knee of the support leg. The centre of gravity should be locate above the knee or just behind.

In frame 2024 the athlete’s ground reaction line is located ahead of the knee. This can be easily ascertained by the position of the front knee. The knee should be located over and forward of the foot at contact with the ground. The puts strain on the hamstring. Force can’t be applied early on contact because the body has to wait until the knee passes ahead of the foot as in frame 2042 then ground reaction forces are directed properly.

Some points of consideration

The incorrect belief held by many that the first stride should be long. This causes athletes to over stride in the first step. A “knee to chest” action will lead to another incorrect or unhelpful consequence. The knee will travel towards the torso causing the torso thigh angle to decrease. Flight time will be increased, which is not the characteristic of the first two strides of elite sprinting. Flight time is minimised while contact time is maximised by the elite sprinter, this will lead to the first two strides having long contact times and naturally shorter stride length.

Select knee joints that much the strength qualities of the athlete, and fall into the angle ranges recommended by Mero, Tellez, Ozolin and Borzov Locate the centre of gravity ahead of the support base in the set position.

Ensure that the first stride isn’t overly long

Minimise the flight time of the first and second stride

Increase the maximal and explosive strength of the quadriceps, gluteus maximus, calf, erector spinae.

Sprint uphill using gradients ranging from 10-50 degrees. Software used for this technical analysis was purchased from Quintic Consultancy Ltd.

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