M Newman

In part 1, we covered the laws of Newton to show how mass, acceleration and force affect sprint performance .  In this article we look at research that suggests that BMI (though not ideal) is nevertheless a useful tool to check that body mass is in an optimum range.

As we know, the acceleration of a sprinter’s body is higher if the force applied to the ground is very large.  We also know that from the previous article, the larger the mass, the harder it becomes to accelerate.  In real life, a relationship between height and body mass has to be taken into consideration since sprinters fall into a range of heights and mass, but ranges that are n’t as varied as the general public.

This relationship can be found by working out the BMI of an individual.  BMI is an abbreviation of Body Mass Index.  We can calculate the BMI by using the following formula:

BMI= weight (Kg)/height² (m²)

Understanding BMI

Body mass index (BMI) is a tool used by health workers, researchers and sports officials as an indicator of overweight and obese conditions.  A major flaw with BMI is its inability to take into account the body fat of an individual.  So we could have an individual who is heavily muscled and very low body fat.  Yet we must respect newton’s second law, which doesn’t discriminate either between fat or lean mass.  Nevertheless, BMI can be used to describe the compactness of a person and serve as a tool to compare sprinters and sprinters to the general public.  BMI can be a useful tool because mass and height affect sprint performance (figure 1).

 

 

In a study by Neils Uth from the University of Aarhus, Aarhus N, Denmark (2005),  the height and body mass data (IAAF Statistics, 1980-2004) of 42 men and 44 women from the all-time 100m top-50 lists (International Association of Athletics Federations, http://www.iaaf.org/statistics/toplists)were compared to those of American (724 male and 663 female) and Danish (1336 male and 1306 female) 20-30 year-old residents. Since there were at that time, a large percenatage of 100m all timers from the US, Uth also compared them to the American population.  Uth gathered the data for the elite sprinters from a wide range of sources (below: appendix I) including the internet, and so some of the data maybe called into question, but never the less, it’s safe to say that in the main, the data is accurate enough for our practical approach.

 

Uth found that the elite sprinters had less differences between each other when it came to height and body mass (in kg) and BMI.  In other words, the 100m event doesn’t allow for big differences in height, body weight and the compactness or BMI between sprinters as a group.  This suggests that there is an ideal range for these three measurements, and if sprinters fall out of these ranges, they are less likely to be successful.   The general population, had much higher BM and BMI due probably to higher body fat.

 

Very low BMIs or very high BMIs in sprinters would limit performance.  If we relate this back to Newton’s second and third law, we could say that a high mass makes acceleration hard to achieve and a lower mass compared to the sprint population, makes it hard to generate  highforces which is  needed to produce greater acceleration, because force is proportional to the cross-section of muscle mass.  We are talking about optimums hear.

 

Looking at the data, the BMI range for sprinters falls between 20-26.5.  The larger numbers tended to be those of taller sprinters, (table 1).

	BM  (KG)	Height (M)	BMI (kg•m-2)
Average	77.02	1.8	23.7
Minimum	64	1.68	20.2
Maximum	91	1.91	26.5

Table 1. Source: Anthropometric Comparison of World-Class Sprinters and Normal Populations.  Uth

BM, Height and BMI data for  50 all time 100m performance list 2005.

 

It would make sense to pay attention to the average numbers; if you are a sprinter, to see where you fit into the range.  If you fall out of the range for body mass (BM) and BMI; then the necessary steps must be taken to fall back in line.

 

In a more recent study, Dyja et al studied elite 100m sprinters at the 2003 Athletics World Championships.  In their study, the authors discussed if stride length or frequency had the greatest influence on sprinting.  They found that stride length was the most important for males and frequency for females respectively.  Body mass and body height were an important factor.  There was a positive link between stride length and body height and weight for male sprinters and female sprinters relied on stride frequency.  The larger the body height and weight; the greater the stride length.  It is important to note that the data in this study; confirms the findings of the study by Uth.  In the study by Dyja, the higher stride length of the faster sprinters could be explained by their more massive bodies.  The average BMI for this study (table 2) is comparative to the Dyja study, showing that the body mass and height relationship changes very little over time.

	BMI (KG)	Height (M)	BMI (kg•m-2)
Average	76.38	1.79	23.8382073
Minimum	60	1.6	N/A
Maximum	88	1.88	N/A

Table 2. Source:  Elite Male and Female Sprinters’ Bodybuild, Stride Length and Stride Frequency. Dyja et al

BM, Height and BMI data.

In a study published in 2005, Weyand and Davis showed that human sprinters in comparsion to long distance runners needed to have a greater body mass because they had to generate up to 2.5 times their body weight at to achieve greater speeds.  Their research used BMI to find the ideal “massiveness”  for all distances from 100m upwards.  They discovered that there was a relationship that was constant (applied across all distances) between BMI and the force runners need to apply to the ground.  To work out the ideal body mass for each event, the researchers used 45 of the fastest athletes in each group over the past 14 years at that time.  The amount of force needed to apply to the ground was related to how fast each event required.  So, in elite sprinting the magic number is 11.00 m/s or faster.  For distance athletes, this was less.  They found that for every 1 m/s increase, both male and female sprinters needed only 2.5kg of body mass.  Weyand found that for every ground force required, at each distance, there was an ideal BMI for each individual.

In Weyand’s study, the ideal BMI is 24.9 from the calculation of ideal body mass for racing.  To calculate your ideal race weight use the following formula as a GUIDE ONLY.

 

Ideal Mass = F x H² x D

 

Where F= 2.5

This is the multiple of body weight that must be supported at stance phase in the 100m.

H²= your height in metres multiplyed by itself.

D= A constant of 10 for men and 9.85 for women.

 

This formula could be used to check if your body weight is close to the optimum.  Of course, body fat must also be optimal.  For men, this falls in within a range of 12-4% and 16-10% body fat for male and female sprinters respectively.

Practical implications.

If you look like a body builder, then its probably not ideal.  Check your body fat percentages, make sure that it is within the norms for sprinters.  Use BMI to keep your lean mass in the ideal range.  Use body building methods carefully and only if you are not within the range.  Once in the range, change the strength training emphasis to max strength and then power.  Use the formula above to calculate ideal race weight.  Remember, this is just an indicator or a guide.

Summary:

The BM, BMI and height of sprinters do not vary much.  There is an ideal range for each.

If you fall within the range then you are ok.

A higher BM and BMI within the identified range influences stride length in a positive manner.

If you are out of the range for BMI then you must take appropriate steps.

An ideal BMI range of 20-25 is ideal.

Depending on the source, the optimal BMI is 23-24.

Body fat must be controlled.

 

APPENDIX I

Source:Anthropometric Comparison of World-Class Sprinters  and sub-10 Performance.  Uth

Mark	Wind  (m/s)	Athlete	Nat	Birth	Venue	Date	Age   (yrs)	Height   (m)	Weight   (kg)	BMI   (kg•m-2)
9.77	1.6	Asafa Powell	JAM	11/11/1982	Athína	14/06/2005	22.6	1.88	87	24.6
9.78	2	Tim Montgomery	USA	28/01/1975	Paris	14/09/2002	27.6	1.78	73	23
9.79	0.1	Maurice Greene	USA	23/07/1974	Athína	16/06/1999	24.9	1.76	80	25.8
9.84	0.7	Donovan Bailey	CAN	16/12/1967	Atlanta GA	27/07/1996	28.6	1.82	83	25.1
9.84	0.2	Bruny Surin	CAN	12/07/1967	Sevilla	22/08/1999	32.1	1.8	81	25
9.85	1.2	Leroy Burrell	USA	21/02/1967	Lausanne	06/07/1994	27.4	1.8	82	25.3
9.85	0.6	Justin Gatlin	USA	10/02/1982	Athína	22/08/2004	22.5	1.85	79	23.1
9.86	1.2	Carl Lewis	USA	1/7/1961	Tokyo	25/08/1991	30.2	1.88	80	22.6
9.86	-0.4	Frank Fredericks	NAM	02/10/1967	Lausanne	03/07/1996	28.8	1.8	73	22.5
9.86	1.8	Ato Boldon	TRI	30/12/1973	Walnut	19/04/1998	24.3	1.76	75	24.2
9.86	0.6	Francis Obikwelu	POR	22/11/1978	Athína	22/08/2004	25.8	1.9	74	20.5
9.87	0.3	Linford Christie	GBR	02/04/1960	Stuttgart	15/08/1993	33.4	1.89	90	25.2
9.87	-0.2	Obadele Thompson	BAR	30/03/1976	Johannesburg	11/09/1998	22.4	1.75	67	21.9
9.87	2	Dwain Chambers	GBR	05/04/1978	Paris	14/09/2002	24.4	1.8	83	25.6
9.88	1.8	Shawn Crawford	USA	14/01/1978	Eugene	19/06/2004	26.4	1.81	75	22.9
9.91	1.2	Dennis Mitchell	USA	20/02/1966	Tokyo	25/08/1991	25.5	1.74	69	22.8
9.92	0.3	Andre Cason	USA	20/01/1969	Stuttgart	15/08/1993	24.6	1.7	70	24.2
9.92	0.8	Jon Drummond	USA	09/09/1968	Indy.IN	12/06/1997	28.8	1.75	72.5	23.7
9.92	-0.2	Seun Ogunkoya	NGR	28/12/1977	Johannesburg	11/09/1998	20.7	1.8	86	26.5
9.92	1	Tim Harden	USA	27/01/1974	Luzern	05/07/1999	25.4	1.78	81.5	25.7
9.93	1.4	Calvin Smith	USA	08/01/1961	Col. Spr.CO	03/07/1983	22.5	1.78	64	20.2
9.93	-0.6	Michael Marsh	USA	04/08/1967	Walnut	18/04/1992	24.7	1.78	68	21.5
9.93	1.8	Patrick Johnson	AUS	26/09/1972	Mito	05/05/2003	30.6	1.77	73	23.3
9.94	0.2	Davidson Ezinwa	NGR	22/11/1971	Linz	4/7/1994	22.6	1.82	80	24.2
9.94	-0.2	Bernard Williams	USA	19/01/1978	Edmonton	05/08/2001	23.5	1.83	81	24.2
9.95	1.9	Olapade Adeniken	NGR	19/08/1969	El Paso	16/04/1994	24.7	1.86	78	22.5
9.95	0.8	Vincent Henderson	USA	20/10/1972	Leverkusen	9/8/1998	25.8	1.74	74	24.4
9.95	1.8	Joshua J. Johnson	USA	10/05/1976	Walnut	21/04/2002	25.9	1.91	91	24.9
9.95	0.6	Deji Aliu	NGR	22/11/1975	Abuja	12/10/2003	27.9	1.87	75	21.4
9.95	1.8	John Capel	USA	27/10/1978	Eugene  OR	19/06/2004	25.6	1.8	81.5	25.2
9.96	1.2	Raymond Stewart	JAM	18/03/1965	Tokyo	25/08/1991	26.4	1.78	73	23
9.96	0.8	Kareem S.Thompson	USA	30/03/1973	Indy  IN	12/6/1997	24.2	1.83	84	25.1
9.97	0	Mark Lewis-Francis	GBR	04/09/1982	Edmonton	04/08/2001	18.9	1.83	85	25.4
9.97	0.6	Uchenna Emedolu	NGR	17/09/1976	Abuja	12/10/2003	27.1	1.83	79	23.6
9.98	0.3	Daniel Effiong	NGR	17/06/1972	Stuttgart	15/08/1993	21.2	1.87	79	22.6
9.98	1.4	Percival Spencer	JAM	24/02/1975	Kingston	20/06/1997	22.3	1.82	68	20.5
9.98	1.6	Leonard Myles-Mills	GHA	09/05/1973	Boise  ID	05/06/1999	26.1	1.69	70	24.5
9.98	0.4	Jason Gardener	GBR	18/09/1975	Lausanne	02/07/1999	23.8	1.78	70	22.1
9.98	0.4	Coby Miller	USA	19/10/1976	Durham NC	02/06/2000	23.6	1.68	68	24.1
9.98	0.2	Kim Collins	SKN	5/4/1976	Manchester	27/07/2002	26.3	1.8	77	23.8
9.99	0.5	Brian Lewis	USA	05/12/1974	Cayenne	04/05/2002	27.4	1.73	71.5	23.9
9.99	1.5	Mickey Grimes	USA	10/10/1976	Zürich	15/08/2003	26.8	1.85	84	24.5

Your email: