Black and white: a comparison
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Is it their high-intensity training that makes black African runners so fast?
In South Africa, top black distance runners usually out-perform their white counterparts. Although they make up just one-fifth of the competitive distance runners in the country, black South Africans capture more than 90 per cent of the top finishing places in races from 5-56K, and black athletes have run 42 of the fastest 50 half-marathons and 34 of the fastest 50 marathons in South African history. Black South Africans have also fared very well in world-wide competition. At the end of 1991, for example, they had run the first-, second-, fifth-, and ninth-fastest times in the world for the half-marathon ('Superior Fatigue Resistance of Elite Black South African Distance Runners', Journal of Applied Physiology, vol. 75(4), pp.1822-1827, 1993).
Just as blacks have dominated competitive running in South Africa, Kenyan runners have ruled the roost on a global basis. Kenyan senior men have won the world cross-country championships for nine consecutive years and filled all five top slots at the 1993 event, while Kenyan junior men have a string of seven straight victories. At this year's world championships in Budapest, Kenyan runners won all four gold medals, and Kenyan junior women captured six of the first seven places in their race, all crossing the finishing line within the brief span of 32 seconds.
At the 1992 Olympics in Barcelona, Kenyan men won eight of the 18-possible medals at distances ranging from 400-10,000 metres (by contrast, just 32 years earlier, only one African won a medal). In the 1988 Seoul Olympics, Kenyans captured the 800-,1500- and 5000-metre races, along with the 3000m steeplechase. Taking into account Kenya's tiny population of 25 million people, the probability of Kenyans winning four gold medals purely by chance has been put at about 1 in 2 billion!
Exercise scientists, coaches and runners have offered an almost infinite number of possible reasons for the superiority of Kenyan and black South African runners, but until now the explanations have been largely theoretical because there has been little comparative scientific testing. However, Tim Noakes and a team of researchers at the University of Cape Town have recently evaluated the fastest black and white South African runners, and their tests reveal a key training difference between the groups, along with several physiological disparities.
Comparing race times
Eleven top-level black athletes, including former world half-marathon record-holder Matthews Temane, Berlin Marathon winner Xolile Yawa, 2:08-marathoner Zithuele Sinqe, and New York Marathon champion William Mtolo participated in the Cape Town study along with nine elite white runners. To be included in the research, each athlete must have sizzled through a mile in less than four minutes or a 5K in faster than 14 minutes, and the runners lOK times averaged 28:30-29:40, with most of the performances achieved at moderate altitude (5900 feet) near Johannesburg.
Although the 3K times (7:57-8:07) and 5K clockings (13:43-13:55) were quite similar between blacks and whites, the blacks were clearly superior over longer distances. Average lOK time for blacks was 28:33 against 29:38 for whites, and average black half-marathon time was 62:39 compared to 67:19 for whites. The Cape Town study also showed that blacks could sustain an intensity of about 93-94% V02max during their lOKs, while whites puttered along at just 87-88% V02max.
Why were blacks better? The difference clearly wasn't in maximal aerobic capacity (V02max) or running economy, since both black and white runners had average V02max values of about 71-72 ml/kg/min and very similar running efficiencies at either 5:40 per mile speed or 4:36 per mile speed (about lOK pace). Muscle fibre composition wasn't the answer, either, since blacks and whites possessed about the same percentage of Type I (slow-twitch) muscle fibres (53-63 per cent of the total). In addition, each group ran about the same total distance (50-60 miles) each week and could attain the same maximal running velocity on the treadmill (about 3:58 per mile).
Slight dietary differences between blacks and whites were apparent. Although each group took in around 3100-3400 calories per day, with about 30 per cent of the calories coming from fat, there was a tendency for blacks to eat more carbohydrate (56 per cent of total calories against 51 per cent for whites), and blacks ate significantly less protein ( 14.5 per cent of calories against 18 per cent for whites). Although daily ingestion of calories was about the same, there was a trend for blacks to eat more if intakes were expressed per pound of body weight. Since the blacks weighed only 123 Ibs while the whites tipped the scales at 154, blacks were actually eating about 28 calories per pound of body weight each day while whites averaged just 22. Still, the blacks were appreciably skinnier than the whites. In fact, several of the black runners had body-fat levels of no more than 3 per cent.
Of course, at 123 Ibs and 5'6', the blacks were considerably smaller than the 5'11',154 Ib whites, which may have given them an edge during long-distance competition. At first glance, larger runners might seem to have certain advantages over their smaller counterparts, including less surface area per unit body mass, and the ability to take longer strides. However, scientific studies suggest that smaller runners do better as race distances increase. For example, Olympic marathon finalists tend to be appreciably smaller than their 5000m brethren. The benefit of being small may reside in the skeletal system. Since bone mass tends to increase exponentially rather than linearly as a function of body height, tall runners must lug around bones which are comparatively heavier than those of their smaller rivals. As a result, the latter can use their energy to run fast instead of burning excess calories hauling big bones.
The biggest difference
However, the key difference between the groups was that blood-lactate levels were considerably lower in the blacks at various running speeds. At a tempo of 4:36 per mile, blacks' blood-lactate concentrations were 24 per cent lower, and 32 per cent lower at actual V02max running speed. Since blood lactate often reflects lactic acid production inside muscle cells, this means that the black athletes experienced less muscle fatigue while running at high-quality speeds.
Moreover, lower lactate not only meant that blacks experienced less tiredness when running at a tough tempo like 4:36 per mile; it also permitted them to run at a higher intensity than the whites without feeling an increased sense of exhaustion. For example, during half-marathon (21.1 K) races blacks were able to run at an intensity of about 90% V02max, which was actually just above the intensity used by whites during their IOK competitions! Small wonder that blacks could cruise through a half-marathon over four minutes faster than whites.
Why did black athletes' muscles produce less lactate? One possible reason may have been the more-intense training carried out by the blacks. Although both groups of runners ran about 50-60 miles per week, blacks blasted through 36 per cent of their training mileage (about 20 weekly miles) at an intensity ABOVE 80% V02max (ie, with heart rates above 87 per cent of maximal). By contrast, whites conducted only 14 per cent of their training above the red-hot 80% V02max level.
This doesn't prove that the more intense training caused the faster race times, of course; there may be other explanations for the black runners' dominance. For example, it' s within the realms of possibility that some as-yet unspecified factor may simply have made the blacks better runners. Better runners tend to train and race more rapidly than less qualified runners; we don't have to automatically assume that it's the higher-speed training which produces the faster times.
However, there's a logical reason for thinking that the faster training speeds of the black runners could have created the key physiological difference between the two groups - the lower lactates of the blacks. To be more specific, the ambitiously intense training of the black runners may have produced a supra-normal training effect in their Type 11A muscle fibres.. Type 11A cells are 'fast twitch' fibres which can degrade glucose to lactic acid to create the energy needed for quick, powerful, 'anaerobic' muscle contractions. The 11As' propensity for lactic acid production may help determine a runner's 'lactate threshold' - the running speed above which blood-lactate levels begin to mount.
The 11A cells resemble their siblings, the 11B fibres, which can also contract powerfully, but the 11As have a unique attribute: they can also develop a substantial capacity to utilize oxygen to create the energy needed for running. As their aerobic potential improves, 11A cells produce less lactic acid, become more fatigue-resistant, and begin to act like a more powerful version of key muscle cell - the Type I ('slow-twitch') fibre. Relatively fast, sustained running (above an intensity of about 80% V02 max), the type of running preferred by blacks during their training sessions, seems to be the best way to stimulate the 11A fibres to become more aerobic and fatigue-resistant. If the 11A fibres of the blacks had a higher aerobic potential than comparable fibres in the whites, this would have indeed allowed the blacks to run faster with less lactate and less fatigue.
Overall, the blacks' running programmes revolved around lots of fartlek running, ample interval workouts on the track, high-quality lOK races, and a firm commitment to run no slower than 3:45 per km during their longer workouts on the roads and trails in the high-veld near Johannesburg. The white athletes trained in a similar manner, with an emphasis on fartlek and interval workouts, but their 5-10 mile road workouts were always conducted at a slower pace.
The secret is in the muscle tissue
Another key difference between the black and white athletes cropped up during an isometric test of leg-muscle strength. Black runners' quadriceps muscles were about 31 per cent weaker than those of the whites, yet the blacks' quads fatigued much less rapidly during the test. In fact, they were able to exert at least 70 per cent of maximal force for 169 seconds during the isometric efforts compared to just 97 seconds for the whites.
'This reinforces our belief that the key difference between black and white South African runners is in the muscle tissue, not the cardiovascular system,' says Tim Noakes. Ordinarily, the lower strength but greater endurance of the blacks' quads might suggest that they had higher percentages of Type I muscle fibres, which aren't very powerful but great at resisting fatigue. However, since the blacks and whites in Noakes' study had equal percentages of Type I and 11 fibres, the difference may again have resided in the blacks superior Type 11A cells, which may have able to thwart fatigue during the isometric test because of their enhanced aerobic characteristics.
The black runners' superiority now seems more mundane than mysterious. Compared to the whites, they may simply have had higher concentrations of key aerobic enzymes inside their Type 11A muscle cells because of their fondness for above-80% V02max training. Yet another mystery remains. How could the black athletes run 2:08 marathons and 60 minute half-marathons on a training diet of 'only' 50-60 miles per week? Don't they realise that great runners need at least 100 miles per week or more?
Actually, there's no mystery, according to Noakes. 'I tell my runners to try to do as much as they can on as little training as possible,' says the South African scientist. 'Obviously this means focusing on intense training, as the black runners in our study did, rather than on grandiose mileage levels.
'The available research shows that intense training is the way to go, as many elite runners have learned. Top marathoners Steve Jones and Rob de Castella revived flagging careers by shifting from high-mileage training to an emphasis on more quality work and less volume. And when Paula Newby-Fraser first went to the United States she began a programme of high-mileage work but had lots of problems until she cut back on her volume and focussed on intensity.
'Most serious runners have a tendency to over-train. Then, when their performances inevitably begin to decline because they've run too much, they do exactly the wrong thing.. They try to pull out of their overtraining tailspin by overtraining even more vigorously. The real answer is to carry out less - but higher-quality - training, as our very best South African runners do.'
Identifying workouts that satisfy the above-80% V02max requirement and light a fire under your Type 11A muscle fibres is easy. 1000-1200m intervals at SK pace, one-mile repeats at 10K pace, and Jack Daniels' tempo runs (20-25 minutes of continuous running at a pace 10-15 seconds per mile slower than 10K race pace) all fill the bill, as does any training session which raises your heart rate beyond about 87 per cent of maximal. Also, the Iynchpin of Kenyan distance runners' training programmes - 10K rambles over dirt roads or forest paths which alternate back and forth between two minutes of running at about 10K race pace and one minute of easy jogging - is perhaps the best of all plus-80% workouts.
However, if you've been training fairly moderately, don't shift suddenly to an intensity-dominated training programme. To avoid burn-outs, it's wise to add no more than one-half mile of above-80% training per week to your existing schedule.
Owen Anderson
At the 1992 Olympics in Barcelona, Kenyan men won eight of the 18-possible medals at distances ranging from 400-10,000 metres (by contrast, just 32 years earlier, only one African won a medal). In the 1988 Seoul Olympics, Kenyans captured the 800-,1500- and 5000-metre races, along with the 3000m steeplechase. Taking into account Kenya's tiny population of 25 million people, the probability of Kenyans winning four gold medals purely by chance has been put at about 1 in 2 billion!
Exercise scientists, coaches and runners have offered an almost infinite number of possible reasons for the superiority of Kenyan and black South African runners, but until now the explanations have been largely theoretical because there has been little comparative scientific testing. However, Tim Noakes and a team of researchers at the University of Cape Town have recently evaluated the fastest black and white South African runners, and their tests reveal a key training difference between the groups, along with several physiological disparities.
Comparing race times
Eleven top-level black athletes, including former world half-marathon record-holder Matthews Temane, Berlin Marathon winner Xolile Yawa, 2:08-marathoner Zithuele Sinqe, and New York Marathon champion William Mtolo participated in the Cape Town study along with nine elite white runners. To be included in the research, each athlete must have sizzled through a mile in less than four minutes or a 5K in faster than 14 minutes, and the runners lOK times averaged 28:30-29:40, with most of the performances achieved at moderate altitude (5900 feet) near Johannesburg.
Although the 3K times (7:57-8:07) and 5K clockings (13:43-13:55) were quite similar between blacks and whites, the blacks were clearly superior over longer distances. Average lOK time for blacks was 28:33 against 29:38 for whites, and average black half-marathon time was 62:39 compared to 67:19 for whites. The Cape Town study also showed that blacks could sustain an intensity of about 93-94% V02max during their lOKs, while whites puttered along at just 87-88% V02max.
Why were blacks better? The difference clearly wasn't in maximal aerobic capacity (V02max) or running economy, since both black and white runners had average V02max values of about 71-72 ml/kg/min and very similar running efficiencies at either 5:40 per mile speed or 4:36 per mile speed (about lOK pace). Muscle fibre composition wasn't the answer, either, since blacks and whites possessed about the same percentage of Type I (slow-twitch) muscle fibres (53-63 per cent of the total). In addition, each group ran about the same total distance (50-60 miles) each week and could attain the same maximal running velocity on the treadmill (about 3:58 per mile).
Slight dietary differences between blacks and whites were apparent. Although each group took in around 3100-3400 calories per day, with about 30 per cent of the calories coming from fat, there was a tendency for blacks to eat more carbohydrate (56 per cent of total calories against 51 per cent for whites), and blacks ate significantly less protein ( 14.5 per cent of calories against 18 per cent for whites). Although daily ingestion of calories was about the same, there was a trend for blacks to eat more if intakes were expressed per pound of body weight. Since the blacks weighed only 123 Ibs while the whites tipped the scales at 154, blacks were actually eating about 28 calories per pound of body weight each day while whites averaged just 22. Still, the blacks were appreciably skinnier than the whites. In fact, several of the black runners had body-fat levels of no more than 3 per cent.
Of course, at 123 Ibs and 5'6', the blacks were considerably smaller than the 5'11',154 Ib whites, which may have given them an edge during long-distance competition. At first glance, larger runners might seem to have certain advantages over their smaller counterparts, including less surface area per unit body mass, and the ability to take longer strides. However, scientific studies suggest that smaller runners do better as race distances increase. For example, Olympic marathon finalists tend to be appreciably smaller than their 5000m brethren. The benefit of being small may reside in the skeletal system. Since bone mass tends to increase exponentially rather than linearly as a function of body height, tall runners must lug around bones which are comparatively heavier than those of their smaller rivals. As a result, the latter can use their energy to run fast instead of burning excess calories hauling big bones.
The biggest difference
However, the key difference between the groups was that blood-lactate levels were considerably lower in the blacks at various running speeds. At a tempo of 4:36 per mile, blacks' blood-lactate concentrations were 24 per cent lower, and 32 per cent lower at actual V02max running speed. Since blood lactate often reflects lactic acid production inside muscle cells, this means that the black athletes experienced less muscle fatigue while running at high-quality speeds.
Moreover, lower lactate not only meant that blacks experienced less tiredness when running at a tough tempo like 4:36 per mile; it also permitted them to run at a higher intensity than the whites without feeling an increased sense of exhaustion. For example, during half-marathon (21.1 K) races blacks were able to run at an intensity of about 90% V02max, which was actually just above the intensity used by whites during their IOK competitions! Small wonder that blacks could cruise through a half-marathon over four minutes faster than whites.
Why did black athletes' muscles produce less lactate? One possible reason may have been the more-intense training carried out by the blacks. Although both groups of runners ran about 50-60 miles per week, blacks blasted through 36 per cent of their training mileage (about 20 weekly miles) at an intensity ABOVE 80% V02max (ie, with heart rates above 87 per cent of maximal). By contrast, whites conducted only 14 per cent of their training above the red-hot 80% V02max level.
However, there's a logical reason for thinking that the faster training speeds of the black runners could have created the key physiological difference between the two groups - the lower lactates of the blacks. To be more specific, the ambitiously intense training of the black runners may have produced a supra-normal training effect in their Type 11A muscle fibres.. Type 11A cells are 'fast twitch' fibres which can degrade glucose to lactic acid to create the energy needed for quick, powerful, 'anaerobic' muscle contractions. The 11As' propensity for lactic acid production may help determine a runner's 'lactate threshold' - the running speed above which blood-lactate levels begin to mount.
The 11A cells resemble their siblings, the 11B fibres, which can also contract powerfully, but the 11As have a unique attribute: they can also develop a substantial capacity to utilize oxygen to create the energy needed for running. As their aerobic potential improves, 11A cells produce less lactic acid, become more fatigue-resistant, and begin to act like a more powerful version of key muscle cell - the Type I ('slow-twitch') fibre. Relatively fast, sustained running (above an intensity of about 80% V02 max), the type of running preferred by blacks during their training sessions, seems to be the best way to stimulate the 11A fibres to become more aerobic and fatigue-resistant. If the 11A fibres of the blacks had a higher aerobic potential than comparable fibres in the whites, this would have indeed allowed the blacks to run faster with less lactate and less fatigue.
Overall, the blacks' running programmes revolved around lots of fartlek running, ample interval workouts on the track, high-quality lOK races, and a firm commitment to run no slower than 3:45 per km during their longer workouts on the roads and trails in the high-veld near Johannesburg. The white athletes trained in a similar manner, with an emphasis on fartlek and interval workouts, but their 5-10 mile road workouts were always conducted at a slower pace.
The secret is in the muscle tissue
Another key difference between the black and white athletes cropped up during an isometric test of leg-muscle strength. Black runners' quadriceps muscles were about 31 per cent weaker than those of the whites, yet the blacks' quads fatigued much less rapidly during the test. In fact, they were able to exert at least 70 per cent of maximal force for 169 seconds during the isometric efforts compared to just 97 seconds for the whites.
'This reinforces our belief that the key difference between black and white South African runners is in the muscle tissue, not the cardiovascular system,' says Tim Noakes. Ordinarily, the lower strength but greater endurance of the blacks' quads might suggest that they had higher percentages of Type I muscle fibres, which aren't very powerful but great at resisting fatigue. However, since the blacks and whites in Noakes' study had equal percentages of Type I and 11 fibres, the difference may again have resided in the blacks superior Type 11A cells, which may have able to thwart fatigue during the isometric test because of their enhanced aerobic characteristics.
The black runners' superiority now seems more mundane than mysterious. Compared to the whites, they may simply have had higher concentrations of key aerobic enzymes inside their Type 11A muscle cells because of their fondness for above-80% V02max training. Yet another mystery remains. How could the black athletes run 2:08 marathons and 60 minute half-marathons on a training diet of 'only' 50-60 miles per week? Don't they realise that great runners need at least 100 miles per week or more?
Actually, there's no mystery, according to Noakes. 'I tell my runners to try to do as much as they can on as little training as possible,' says the South African scientist. 'Obviously this means focusing on intense training, as the black runners in our study did, rather than on grandiose mileage levels.
'The available research shows that intense training is the way to go, as many elite runners have learned. Top marathoners Steve Jones and Rob de Castella revived flagging careers by shifting from high-mileage training to an emphasis on more quality work and less volume. And when Paula Newby-Fraser first went to the United States she began a programme of high-mileage work but had lots of problems until she cut back on her volume and focussed on intensity.
'Most serious runners have a tendency to over-train. Then, when their performances inevitably begin to decline because they've run too much, they do exactly the wrong thing.. They try to pull out of their overtraining tailspin by overtraining even more vigorously. The real answer is to carry out less - but higher-quality - training, as our very best South African runners do.'
Identifying workouts that satisfy the above-80% V02max requirement and light a fire under your Type 11A muscle fibres is easy. 1000-1200m intervals at SK pace, one-mile repeats at 10K pace, and Jack Daniels' tempo runs (20-25 minutes of continuous running at a pace 10-15 seconds per mile slower than 10K race pace) all fill the bill, as does any training session which raises your heart rate beyond about 87 per cent of maximal. Also, the Iynchpin of Kenyan distance runners' training programmes - 10K rambles over dirt roads or forest paths which alternate back and forth between two minutes of running at about 10K race pace and one minute of easy jogging - is perhaps the best of all plus-80% workouts.
However, if you've been training fairly moderately, don't shift suddenly to an intensity-dominated training programme. To avoid burn-outs, it's wise to add no more than one-half mile of above-80% training per week to your existing schedule.
Owen Anderson
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