Tuesday, 3 July 2012

Physical Characteristics of sprinters and runners



Sprinters are clearly differentiated from endurance athletes. Simply look at their physiques and you will note the remarkable muscle bulk of the sprinter in the key prime movers especially. What we are seeing is a sport or selective hypertrophy in the major prime movers of the sprint athlete (1). In contrast, the endurance athlete does not display such muscle hypertrophy. He or she tends to be lighter, less bulked and even drawn looking.


Posture – differences between sprinters and endurance athletes


In effect when we compare their posture we may also see clear differences. The endurance athlete – especially the long distance runner, may not have the same well developed upper body muscle mass and may as a result display some form of kyphosis about the upper back and neck areas. In contrast the sprinter tends to be very well developed in the upper back area displaying good scapula positioning on the upper back. Also the sprinter may seem to display a notable lumbar lordosis (excessive arch in the lower back) that may not be as evident in the distance runner. This may be related to the greater muscle bulk in the gluteal region for the sprinter as opposed to a real lordotic curve.
Later in this study we will return to this often overlooked area for development of speed. We are now more aware of the importance of having a balanced body (in terms of mobility and stability and function) for efficient and optimum movement. This imbalance may actually impede the optimal functioning of the athlete or player. For example, if the hip flexors are overly tight then the gluteal muscles (the powerful leg extensor muscles) may not be operating as effective as they possibly could.  In other words instead of a 4 cylinder engine moving the body only three may be working resulting in a reduced power output. Thus we recommend accessing the functional competence of our athletes in order to ensure that what we may be seeing in their posture is not impeding their function.

Stature – does height matter in speed?


When we compare the stature of the endurance and sprint athletes we will find many short stature top class endurance athletes. They typically are of East African origin and while their Caucasian counterparts seem to be taller the endurance athlete can be shorter than the sprinter in general. However, the sprinter also comes in a wide variety of sizes. A number of authors note that size has no influence on running at a constant speed (2). This tells us that endurance athletes can be either short or tall and really size is inconsequential in terms of endurance performance.
Being tall is however a disadvantage when it comes to running uphill. Also tall athletes may be a disadvantage when it comes to acceleration. In other words the shorter athlete or player will be better able to accelerate and control their own body weight compared to a taller individual. We can also see practical support for this in Gymnastics where the athletes are relatively small compared to the field sports and court sports players. Certainly, where sports such as basketball and volleyball are concerned then stature is an important physical characteristic. Also, when it comes to flying or top speed, taller athletes may have an advantage. So when it comes to looking at the stature of the sprint athletes in the Olympic 100m final this summer, do not be surprised that the athletes lining up at the start might very well be tall, medium and short in stature. 

Size – key strength and power factor


A bigger athlete in terms of overall size and body mass or weight will have advantages in several physical areas over a lighter smaller one. For example large athletes are commonly found in the throwing events. The ability to accelerate an external object is proportional to height squared. This means that the taller athlete’s arms will provide a mechanical advantage that allows a greater torque, for example, in the discus turn. In general the heaviest weightlifters lift the most weight and this is so simply because they have so much mass and consequently strength, that they can effectively overcome the inertia (the tendency of a body to stay at rest) of the load.
In contrast we have noted already that in sports where lifting one’s own body is important – such as in Gymnastics – size may be a disadvantage. This is why we see so many small but powerful and mobile gymnasts. In other sports though, it is not that simple. For example, in pole vaulting where acceleration and speed are important at take off and where reach height is added to the equation as well as handling one’s own body weight, then we can see how stature is a more complex combination. Being tall facilitates a higher reach height at take off and this is a distinct advantage for the pole-vaulter. Even though handling one’s own body weight is an advantage to the smaller athlete and handling body weight during the pole vault is an important skill, we are now seeing the dominance of the tall pole vault athlete as opposed to the shorter athlete.
When it comes to heat dissipation small stature individuals tend to be better at off loading heat due to the smaller body surface area. This is actually an advantage in endurance events where the cardiac output is preserved as heat is unloaded easier. In contrast there is better heat conservation in large individuals. This is obviously an advantage in activities where cold is a problem.

Physiology – key differentiating characteristics


We have already highlighted the key structural differences in terms of muscle fibre type between the endurance athlete and the sprinter. As you will recall, the sprinter is the one endowed with a dominance of the fast-twitch fibre. This ‘white’ fibre has several speed producing characteristics that make it ideally suited for speed and power performance. The accompanying table compares some of the key physiological differences between slow and fast twitch fibres. Understanding these differences believe it or not does help us in choosing and designing training for the sprint and endurance athlete.



Nomenclature
Slow Twitch (A)
Phasic Type I
Fast Twitch(B)
Tonic Type II
Structure
Colour
Red
White
Fibre diameter
Small
Large
Mitochondria content
High
Low
Capillary content
High
Low
Sarcoplasmic reticulum
Simple
Complex
Fibre content per motor unit
Low
High
Biochemistry
Calcium
Low
High
Myosin ATPase
Low
High
Glycolytic capacity
Low
High
Oxidative capacity
High
Low
Mechanical –Function
Contraction speed or Twitch
Slow
Fast
Relaxation speed
Slow
Fast
Fatigue
Low
High
Force generation
Low
High



Table 1. Structure, Biochemistry and Function of Slow and Fast twitch fibres.

Table 1 identifies some key functional characteristics that are indeed giving the sprinter an advantage in terms of speed. The speed of contraction is greater in the fast twitch muscle, the relaxation time is faster as well and the capacity to generate force is also higher than in the endurance fibre profile.
We can test the athlete to determine if he or she has a predominant fast or slow twitch profile. The Counter Movement Jump and the Squat Jump may be used to estimate the dominance of fibre type (3). Completing both jumps using an electronic timing mat, it is possible to estimate the athlete’s leg extensor fibre type to within 5-10% accuracy according to Bosco (3). However, if you do not have access to such testing equipment simply completing a wall reach vertical jump will tell you if you are lucky enough to be endowed with explosive qualities. Other authors provide a neat table that shows that if you are female and can jump over 46 cm (18 inches) vertically then you are likely to have a high fats twitch fibre composition (4). For males having a vertical jump height over 53 cm (21 inches) suggests that you have a high fast twitch fibre composition.
Table 2 below illustrates the range of fast twitch muscle fibre in athletes from different sports. To determine this information, the researchers used what we call a needle biopsy technique to extract some muscle fibre samples. The muscle biopsy was generally taken from the quadriceps muscle which is a mix of both fast and slow fibres. 


Fast twitch estimations for athletes from different sports


Sport
Men (% of fast twitch)
Women (% of fast twitch)
100-200m
48-80%
72-75%
800m
40-64%
25-55%
Shot put
50-88%
45-52%
Distance runners
25-45%
25-50%
Untrained
25-62%
25-72%

Table 2. Fast twitch profile of selected athletes (3).

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References

  • 1.       Bompa et al. Human Kinetics. 2003.
  • 2.       Watson & Hennessy. Longman Press. 1994.
  • 3.       Bosco C. Italian Society of Sport science. 1999.
  • 4.       Sharkey & Gaskill. Human Kinetics. 2006.

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