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Body dimensions, exercise capacity and physical activity level of adolescent Nandi boys in western Kenya

Annals of Human Biology

March 2004
31(2):159-73

DOI:10.1080/03014460410001663416

Source
PubMed

Authors:

Dirk Lund Christensen

University of Copenhagen

The aim of this study was to characterize untrained Nandi boys (mean age 16.6 years) from a town (n = 11) and from a rural area (n = 19) in western Kenya (altitude approximately 2000 m.a.s.l.) in regard to their body dimensions, oxygen uptake and physical activity level. The town boys had a mean maximal oxygen uptake (VO(2 max)) of 50 (range: 45-60) mL kg(-1) min(-1), whereas the village boys reached a value of 55 (37-63) mL kg(-1) min(-1) ( p<0.01) in VO(2 max). The running economy, determined as the oxygen cost at a given running speed, was 221 mL kg(-1) km(-1) (597 mL kg(-0.75) km(-1)) for town as well as for village boys. The body mass index (BMI) was very low for town as well as for village boys (18.6 vs 18.4 kg m(-2)). The daily mean time spent working in the field during secondary school and doing sports were significantly higher in village boys compared to town boys (working in the field: 44.2 (0-128) vs 1.3 (0-11) min, p<0.01; sports: 32.0 (11-72) vs 12.8 (0-35) min, p<0.01, respectively). A positive correlation between the daily time spent doing sports and VO(2 max) was found when pooling the data from the town and the village boys (R = 0.55, p<0.01). It is concluded that the body dimensions of adolescent Nandi town and village boys corresponds well with findings in Kenyan elite runners. They are very slender with relatively long legs. In addition, the VO(2 max) of the village boys was higher than that of the town boys, which is probably due to a higher physical activity level of the village boys during secondary school.

…

BMIs of Nandi town and village boys and of adolescent boys of different ethnic origin. a and b refer to two different investigations of the same people presented in table 7.

…

. Running economy of Nandi town and village boys measured at 10.15 and 10.79 km h À1 on average, respectively. Mean values AE SD and ranges are given.

…

. Summary table of studies examining height, mass and BMI of adolescent boys of different ethnic origin.

…

Major activities before and during the years at primary school in town and village boys. The percentage of boys involved in each activity in varying number of days is given. The data are based on interviews of 11 town boys and 15 village boys.

…

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Body dimensions, exercise capacity and physical activity level of

adolescent Nandi boys in western Kenya

H.B.Larsen,D.L.Christensen,T.Nolanand H. Sndergaard

The Copenhagen Muscle Research Centre, Rigshospitalet and University of Copenhagen, Denmark

Received 12 May 2003; in revised form 2 December 2003; accepted 9 December 2003

Summary. The aim of this study was to characterize untrained Nandi boys (mean age 16.6

years) from a town (n¼11) and from a rural area (n¼19) in western Kenya (altitude

2000 m.a.s.l.) in regard to their body dimensions, oxygen uptake and physical activity

level. The town boys had a mean maximal oxygen uptake (VO

2max

) of 50 (range: 45–60)

mL kg

1

min

1

, whereas the village boys reached a value of 55 (3763) mL kg

1

min

1

(p<0.01) in VO

2max

. The running economy, determined as the oxygen cost at a given

running speed, was 221 mL kg

1

(597 mL kg

0.75

1

) for town as well as for village

boys. The body mass index (BMI) was very low for town as well as for village boys

(18.6 vs 18.4 kg m

2

). The daily mean time spent working in the ﬁeld during secondary

school and doing sports were signiﬁcantly higher in village boys compared to town boys

(working in the ﬁeld: 44.2 (0–128) vs 1.3 (0–11) min, p<0.01; sports: 32.0 (11–72) vs 12.8 (0–

35) min, p<0.01, respectively). A positive correlation between the daily time spent doing

sports and VO

2max

was found when pooling the data from the town and the village boys

(R¼0.55, p<0.01). It is concluded that the body dimensions of adolescent Nandi town and

village boys corresponds well with ﬁndings in Kenyan elite runners. They are very slender

with relatively long legs. In addition, the VO

2max

of the village boys was higher than that of

the town boys, which is probably due to a higher physical activity level of the village boys

during secondary school.

1. Introduction

During the past 35 years, African runners or runners of African ancestry have

produced some of the most remarkable results in athletic events at world-class level.

While the West Africans have excelled in short distance races (100–400 m), the

East Africans, especially Kenyans, have excelled in middle-distance (800–1500 m)

and steeplechase, and also, together with the Ethiopians, in long-distance races

(5000 m—marathon). In fact, >55% of the all-time top 20 lists for men in distances

from 800 m to the marathon are Kenyans. In addition, the majority of the Kenyan

achievements has been produced by a group of eight small tribes called Kalenjin,

which today number only 3.5 million people. Among the Kalenjin tribes, the Nandi

tribe has shown the most profound results. Although this tribe constitutes only 2%

of the Kenyan population, it is the most successful single tribe in Kenya to date

with respect to performance in running. The reasons for this dominance are still

not known, but factors that may play a role are genetic endowment, upbringing and

training.

Success in running events depends on several factors. These include both aerobic

and anaerobic capacities for energy turnover, muscular strength, running economy

as well as biomechanical, psychological and sociological characteristics. So far,

only two studies have examined some physiological diﬀerences when comparing

ANNALS OF HUMAN BIOLOGY

MARCH–APRIL 2004, VOL. 31, NO. 2,159–173

Annals of Human Biology ISSN 0301–4460 print/ISSN 1464–5033 online #2004 Taylor & Francis Ltd

http://www.tandf.co.uk/journals

DOI: 10.1080/03014460410001663416

Kenyan athletes with athletes of non-African descent (Saltin et al. 1995a,b).

These studies revealed that Kenyan elite runners have a very high VO

2max

(79.9 mL kg

1

min

1

), but not higher than that observed in Scandinavian elite

runners (79.2 mL kg

1

min

1

). In addition, the studies further demonstrated that

untrained Kenyan boys from a town had a VO

2max

similar to that of untrained

Danish boys described by Andersen et al. (1987). However, Kenyan elite runners

are fostered in small villages and rural areas where physical activity levels are

thought to be higher than in towns. Whether this is true and the degree to which

this may contribute to the development of physiological properties crucial for

performance in middle- and long-distance running is not known. Furthermore, the

studies by Saltin et al. (1995b) revealed that Kenyan elite runners had a highly

proﬁcient running economy compared to Scandinavian elite runners as judged

from oxygen uptake at sub-maximal speeds. Moreover, Kenyan elite runners had

a lower body mass index (BMI) compared to the Scandinavian runners. Dotan et al.

(1983) have demonstrated a moderate relationship between the BMI and marathon

running performance. However, the underlying physiological reasons for this are

not known. Classical studies of human locomotion (Fenn 1930, Cavagna et al.

1964) have indicated that the work of moving the limbs comprises a substantial

part of the metabolic cost of running, just as load-carrying experiments (e.g.

Myers and Steudel 1985) have shown that carrying a few grams of mass on the

feet/ankle evokes an increase in the metabolic rate of running. This indicates that a

low leg mass is advantageous for the running economy. Therefore, it can be specu-

lated whether the low BMI of the Kenyan elite runners implies that these have more

slender limbs than Caucasian elite runners and whether this relates to the observed

superior running economy of the Kenyan runners. In addition, to what degree the

low BMI of Kenyan elite runners compared to Scandinavian elite runners is due

to selection or is a general feature of untrained Kenyans is unknown. Furthermore,

no information is available at present about the running economy of untrained

Kenyans.

In this light the purpose of the present study was to describe body dimensions,

running economy, aerobic power, and related variables and relate them to habitual

daily physical activity level of Nandi town and village boys in western Kenya. The

hypothesis was that the characteristics of east African elite distance runners can be

observed in adolescent Nandi boys regardless of where they live.

2. Methods

2.1. Subjects

Sixty Kenyan boys volunteered for the present study. Before entering the study

all subjects ﬁlled in questionnaires encompassing questions related to (a) tribe,

(b) transportation to and from school during childhood, (c) leisure-time activities

and (d) coach-organized training. Based on the questionnaires, 11 town boys and 19

village boys all belonging to the Nandi tribe (veriﬁed to the level of grandparents)

not previously engaged in any kind of organized endurance training were selected.

Three Nandi boys were excluded due to illness, while one was excluded due to

insuﬃcient sexual maturation. The remaining 26 boys were excluded due to the

fact that they were not Nandies. All subjects were recruited from two secondary

day schools. The town boys were recruited from Uasin Gishu High School in the

town of Eldoret located in the western part of Kenya, on a plateau at an altitude of

2000 m.a.s.l. Except for two subjects who were raised in a town or city, they were

160 H. B. Larsen et al.

all born and brought up in the rural area around Eldoret. At the age of 14 years,

nine of the subjects had moved to Eldoret in order to begin their studies at secondary

school, while the remaining two subjects continued living in the countryside. The

village boys were recruited from Kamobo Secondary School located in the Nandi

district about 50 km south-west of Eldoret at the same altitude as this town. All

subjects were living in the rural area within a radius of 4 km from the school. Before

entering the study, sexual maturation was assessed by one of the investigators who

evaluated the development of secondary sex characteristics (pubic hair). The method

described by Marshall and Tanner (1970) was employed. The subjects who were

in stage 3 (PH3) or lower were excluded from the study. The vast majority of the

boys who participated were in stage 5 (PH5), while a few boys were in stage 4 (PH4).

The Ethics Committee of the Faculty of Health Sciences at Moi University, Eldoret,

Kenya, approved the study. All subjects and their parents were fully informed orally

as well as in writing of the experimental procedures and possible risks connected with

the study and gave written consent. All subjects were informed that they were free to

withdraw from the study at any time. All subjects were studied at altitude (baro-

metric pressure 595 mmHg). Some physical characteristics, BMI and anthropo-

metric measures (leg length, lower leg length and circumference) of the subjects

are given in table 1.

2.2. Protocol and methods

The date of birth of each subject was assessed by oral information. All subjects

knew in which year they were born. However, one town boy and one village boy

were unaware of their exact date of birth, which was then decided to be 1 July. Body

mass was assessed by using an electronic scale calibrated with known weights. Height

was measured to the nearest millimetre with eye (outer ear oriﬁce being horizontal).

Leg circumference was measured by using a string. Other body dimensions were

measured by using a folding-rule. Lower and total leg length, deﬁned as the distance

from the ground to the middle of the ﬁbula head and the distance from the ground to

the anterior superior iliac spine, respectively, were measured in all boys. In addition,

the distance from the ground to the middle of the lateral malleolus was measured.

All subjects went through sub-maximal and maximal tests on the treadmill. Prior

to these tests, all boys performed two or three (more than 50 min in total) practice

sessions at diﬀerent days at three diﬀerent speeds each day to accustom them to

running on a treadmill as well as with the equipment used to determine the respira-

tory variables. The exercise protocol on the treadmill consisted of a 10-min warm-up

Table 1. Some physical characteristics, BMI and anthropometric measures (leg length, lower leg

length and lower leg circumference) of Nandi town and village boys. Mean valuesSD and

ranges are given.

Age

(years)

Mass

(kg)

Height

(cm)

BMI

(kg m

2

)

Leg length

(cm)

Lower leg

length (cm)

Lower leg

circumference

(cm)

Town boys 11 16.6 0.7 53.8 8.1 169.5 7.7 18.6 1.5 101.25.3 45.5 2.9 –

15.7–17.5 41.3–64.7 157–183 15.7–20.5 94–113 41–51

Village boys 19 16.6 0.8 53.3 5.3 170.4 7.9 18.4 1.6 101.9 4.9

45.4 3.0

31.9 1.7

15.2–18.4 45.4–63.2 158–187 15.3–20.5 94–111 43–54 29.8–34.9

yn¼15; zn¼12.

Physical characteristics of Kenyan Nandi boys 161

at speeds from 6.0 to 10.0 km h

1

. After 7–10 min of rest, the subjects ran 7 and

6 min, respectively, at two diﬀerent individual speeds, with 0.5–1.0 min of rest in

between. The two speeds were chosen to demand a heart rate of 150155

(6.0–11.5 km h

1

) and 165–175 (8.0–14.0 km h

1

) beats per minute (b.p.m.),

respectively. In order to be able to calculate exact running economy, body mass

including test equipment was measured immediately before and after the test.

After 10 min of rest, the maximal test was performed at speeds from 13.0 to

17.5 km h

1

. The test started without inclination, and every second minute the

inclination was raised by 2% until exhaustion. During the last 1.5 min at each

sub-maximal speed, the expired air was collected in Douglas bags, while it was

collected continuously during the maximal test. Heart rate was measured continu-

ously during all tests, while a blood sample was taken from a superﬁcial arm vein

at rest and during the last 15 s of each sub-maximal run or immediately after this.

Furthermore, blood samples were taken at rest shortly before the maximal run and 1

and 3 min, respectively, after this test. The oxygen uptake was calculated after meas-

uring the volume of expired air with a gasmeter (London Gasmeter Co.) calibrated

with a Tissot spirometer and the fractions of O

and CO

using a Servomex S-3 A/I

and a Beckman LB-2, respectively. Heart rate was monitored with a telemetric

system (Polar Accurex Plus, Polar Electro, Finland). The blood samples were

analysed for lactate and ammonia (Kun and Kearney 1974). Haemoglobin was

determined spectrophotometrically on blood taken from a ﬁngertip or from a super-

ﬁcial arm vein after the subjects had been resting in supine position for 5–10 min.

2.3. Physical activity level

To obtain information about the boys’ physical activity level during childhood,

each of them was interviewed by one of the investigators using a standardized

formula encompassing questions related to (a) duties at home involving physical

activity, (b) transportation to and from school, (c) sport activities during a day in

school, and (d) leisure time activities. Furthermore, during secondary school, the

boys ﬁlled in questionnaires of their habitual physical activity level from hour to

hour during 6 days on the average. Two diﬀerent kinds of questionnaires were

employed. In one of these the subjects stated how far they were walking/running

each day to and from school and which kind of physical activities they were doing

during the day. In the other questionnaire the subjects reported how many minutes

they were physically active daily at ﬁve diﬀerent activity levels from lying/sitting to

fast running. Using the initial questionnaires, which the subjects ﬁlled in before

entering the study, checked up the information concerning distance between home

and school from the ﬁrst of these questionnaires. In addition, to obtain more exact

measures of the physical activity level of each subject, heart rate was recorded every

minute during 24 h using telemetric heart rate monitors.

2.4. Statistics

The statistics included the calculations of means, standard deviation and test for

group diﬀerences (Siegel 1956). The signiﬁcance of diﬀerences between conditions

was tested using the paired t-test. Diﬀerences between conditions were considered

signiﬁcant at the 95% conﬁdence level.

162 H. B. Larsen et al.

3. Results

3.1. Physical characteristics, BMI and anthropometric measures (table 1)

Both the town and the village boys were small and light, and their BMIs were 18.6

and 18.4 kg m

1

, respectively. Both groups of boys had long and slender legs, with no

diﬀerence between groups.

3.2. Exercise data and haemoglobin (tables 2 and 3)

The maximal oxygen uptake of the town boys was 50.2 mL kg

1

min

1

, while the

corresponding value for the village boys was 10% higher (55.1 mL kg

1

min

1

p<0.01). Of note is the large range of VO

2max

observed in the village boys. There

were no other diﬀerences in the maximal exercise values between the town and

village boys. The values of haemoglobin were low (8.8 vs 8.6 mmol L

1

, respectively),

taking the altitude into consideration. The village boys could run at a slightly higher

sub-maximal speed with given sub-maximal heart rate and blood lactate level com-

pared to the town boys.

3.3. Running economy (table 4)

The oxygen cost of running was the same for the town and village boys when

expressed per kilogram (220.6 vs 221.1 mL kg

1

) as well as per 0.75 kg (597.4 vs

596.4 mL kg

0.75

1

) of body weight.

Table 2. VO

2max

, maximal heart rate (HR

max

) and peak blood lactate (Hla

max

) and ammonia

(NH

3max

) concentration in untrained Nandi town or village boys. Mean values SD and ranges

are given.

2max

n(L min

1

) (mLkg

1

min

1

) (mL kg

0.75

min

1

)

max

(b.p.m.)

Hla

max

(mmol L

1

)

3max

(mmol L

1

)

Town boys 11 2.71 0.51 50.2 4.2 135.9 13.8 196.9 11.0 9.8 2.5

}

226.8 65.9

1.98–3.58 45.4–60.2 121.7–167.3 172–206 7.1–13.9 114–328

Village boys 19 2.94 0.46 55.15.3

148.9 15.6

197.1 6.4 9.4 1.9** 218.7 54.6**

1.98–3.87 37.4–62.8 100.8–174.9 186–209 6.2–12.8 113–281

Signiﬁcantly diﬀerent from town boys: yp<0.01; zp<0.02.

}n¼9; ôn¼8; ** n¼13.

Table 3. Sub-maximal test speeds, heart rate, blood lactate and ammonia concentration for Nandi

town and village boys. Mean values SD and ranges are given.

Test speed Heart rate Blood lactate NH

(km h

1

) (b.p.m.) (mmol L

1

)(mmol L

1

)

Town boys 10 8.3 1.5 152 7.0 2.0 0.8

89.6 17.9

6.0–10.5 139–167 1.0–3.4 72.0–128.5

10 10.21.4 171 10.8 2.7 1.1

98.0 25.1

8.0–12.0 161–179 1.4–4.5 70.0–151.0

Village boys 19 8.7 1.0 153 9.0 1.9 0.4

93.4 18.0

7.5–11.5 139–169 1.4–2.9 58.5–117.5

19 10.81.0 170 8.2 2.5 0.7

101.3 22.7

9.5–14.0 152–186 1.2–3.3 66.0–133.0

yn¼8; zn¼15.

Physical characteristics of Kenyan Nandi boys 163

3.4. Habitual physical activity during childhood (table 5)

Except for two town boys who were born and raised in a town/city, all town boys

as well as all village boys reported that they had been living in a village or a rural

area during childhood. The mean distance between home and primary school was 2.5

(0.5–3.5) km and 2.1 (1.0–4.0)km, respectively, for town and village boys. One

town boy reported that he was running to school daily in the morning, two town

boys were running to school if they were late, while two town boys reported that they

walked/ran to and from school. Six town boys reported that they were walking to

school, while nine town boys were walking back home every day. Four village boys

reported that they were walking/running to and from primary school, while 11

village boys reported that they were walking both ways. At the age of 4–12 both

town and village boys reported that they had many duties at home. The main duties

were cattle herding and ﬁeld work (table 5). Both groups of boys were most active

herding cattle and working in the ﬁeld before starting primary school. Some of the

ﬁeldwork was made using manual power, while some was made using engine power.

Other duties included washing clothes, shopping and fetching water and ﬁrewood.

No diﬀerences were observed between the two groups of boys in any physical activity

related to duties at home. In addition, both town and village boys were active doing

sports while at school as well as after school, but no diﬀerences were observed

between the two groups (table 5).

3.5. Habitual physical activity level during secondary school (table 6,ﬁgure 1)

The mean distance between home and secondary school was 2.5 (1.0–4.0) and

3.0 (1.04.0) km, respectively, for town and village boys. Both groups of boys were

Table 5. Major activities before and during the years at primary school in town and village boys.

The percentage of boys involved in each activity in varying number of days is given. The data are

based on interviews of 11 town boys and 15 village boys.

Cattle herding Fieldwork

Sports activities after

start at primary school

Before start

at primary

school

(%)

After start

at primary

school

(%)

Before start

at primary

school

(%)

After start

at primary

school

(%)

During a day

in school

(%)

After school

time

(%)

Almost

every day

town boys 64 36 55 27 45 27

village boys 73 33 27 27 53 20

3–5 days/week town boys 18 36 36 9 18 18

village boys 13 27 27 40 27 33

<2 days/week town boys 18 27 9 55 27 45

village boys 13 40 47 33 20 40

Table 4. Running economy of Nandi town and village boys measured at 10.15 and 10.79 km h

1

on average, respectively. Mean values SD and ranges are given.

Test speed

(km h

1

) (mL kg

1

min

1

) (mL kg

1

) (mL kg

0.75

1

)

Town boys 10 10.15 1.4 37.0 3.9 220.6 21.5 597.4 56.0

8.0–12.0 32–45 179–246 509–683

Village boys 14 10.79 1.2 39.6 3.5 221.1 17.9 596.4 39.2

9.5–14.0 35–49 187–237 511–669

164 H. B. Larsen et al.

walking about 3 km on average per day (table 6). Even though the distance covered

daily by running was greater for the village boys compared to the town boys, none of

the two groups of boys did much running (0.3 vs 0.9 km day

1

,p<0.05). The time

spent daily doing sports activities (mainly football and volleyball) was approximately

half an hour for the village boys. This was 150% more than for the town boys

(p<0.02). The village boys were working for about three-quarters of an hour

in the ﬁeld per day. This was considerably more than the town boys, of whom

only one subject was working in the ﬁeld ( p<0.01). Of note is also that the time

spent daily herding cattle was very limited for both groups of boys. The 24 h heart-

rate recordings in nine village boys demonstrated a rather low physical activity level

of these boys. Thus, a heart rate above 120 beats min

1

was achieved only during

23 min day (24 h)

1

(ﬁgure 1).

4. Discussion

The body proportions of the Nandi boys are indeed much smaller compared to

Caucasian boys of almost the same age (Andersen 1994). The height of the Kenyan

Figure 1. Mean duration (mean SD) of heart rates at diﬀerent frequencies recorded every minute

during 24 h in nine Nandi village boys.

Table 6. Habitual daily physical activity during six randomly selected days in secondary school for

town and village boys. Mean values SD and ranges are given.

Walking Running Sports activities Work (ﬁeld) Cattle herding

(km day

1

) (km day

1

) (min day

1

) (min day

1

) (min day

1

)

Town boys 9 3.3 2.4 0.3 0.4 12.8 11.8 1.3 3.8 0.0 0.0

0.05.2 0.01.1 0–35 011 00

Village boys 13 2.9 1.7 0.90.9

32.0 17.3

44.2 41.6

9.0 14.9

0.56.5 0.02.8 11–72 0128 047

Signiﬁcantly diﬀerent from town boys: yp<0.05; zp<0.01.

Physical characteristics of Kenyan Nandi boys 165

boys is 9 cm lower, while the body mass is 12 kg lower. In addition, the BMI is

2kgm

2

lower compared to the Caucasian boys, which shows that the Nandi boys

have a much more slender body shape than the Caucasian boys (table 7, ﬁgure 2). In

addition, except for the Caucasians, the Nandi boys have similar height or tend to be

marginally taller compared to the other ethnic groups presented in table 7, whereas

the body mass of the Nandi boys, except for the Indians (Pathmanathan and

Prakash 1994), is similar to or lower compared to the other groups of boys.

However, the fact that the Nandi boys are relatively high, when taking their low

mass into consideration, implies that they have a very low BMI compared to almost

all the other groups of boys (ﬁgure 2). In fact, the only group with a BMI that tends

to be lower than that of the Nandis is the Indian boys. However, these boys are 0.8

years younger than the Nandi boys. The BMI of 17-year-old South African Indian

boys (Walker et al. 1989) actually tends to be higher than the BMI of the Nandi

boys. Three other ethnic groups of boys (Ethiopians (Peters et al. 1987), black South

Africans from the rural area (Walker et al. 1980) and Hong Kong Chinese (Barnett

et al. 1995) (table 7)) tend to have higher BMIs than the Nandi boys. Ethiopians as

well as black South Africans are of interest since both peoples have produced some

remarkable results in distance running. As the number of Ethiopian boys measured

Table 7. Summary table of studies examining height, mass and BMI of adolescent boys of diﬀerent

ethnic origin.

Study Subject population n

Age

(years)

Height

(cm)

Body mass

(kg)

BMI

(kg m

2

)

Kobayashi et al. 1978 Japanese 43 17.2 168.9 58.2 20.4

Barnett et al. 1995 Hong Kong Chinese 22 16.1 165.7 52.7 19.2

Walker et al. 1989 South African Indian 77 17 169.9 54.8 19.0

Pathmanathan and

Prakash 1994

Indian 20 15.8 164.9 48.8 18.0

Wacharasindhu et al. 2002 Thai 53 16.6 170.8

Andersen 1994 Danish 4511 17 179.6

Danish 4549 17 66.0

Danish 4464 17 20.4

Becker-Christensen 2002 Greenlanders 16 16.9 169.9 63.9 22.1

da Silva and Malina 2000 Brazilian 125 15.0 166.7 55.1 19.7

Sichieri et al. 1995 Brazilian 608 17 167.8 57.4

20.4

Spurgeon and Meredith

1979

US blacks 219 15 167.2 56.6 20.2

US whites 186 15 169.4 57.1 19.9

Rosner et al. 1998 US blacks 1417 17 22.8

US whites 1680 17 22.7

US Hispanic 251 17 23.2

Zavaleta and Malina 1980 Mexican–American 55 16.5 168.2 64.3 22.7

Mukhtar et al. 1989 Libyan 44 17 172.4 66.4 22.3

Ibu et al. 1986 Nigerian 26 17 165.6 60.8 22.2

Peters et al. 1987 Ethiopian 7 16–17 167.9 53.9 19.1

Walker et al. 1980 Black South Africans,

rural

148 17 167.0 53.5 19.2

Black South Africans,

urban

151 17 168.2 55.9 19.8

Present study Kenyan Nandi

town boys

11 16.6 169.5 53.8 18.6

Kenyan Nandi

village boys

19 16.6 170.4 53.3 18.4

ycalculated from BMI and height.

166 H. B. Larsen et al.

in the study by Peters et al. (1987) is small (n¼7), and Ethiopian adults (n¼156)

investigated in the same study had BMIs of 18.8 kg m

2

, while Kenyan elite

runners (primarily Nandis) had 19.2 kg m

2

(Saltin et al. 1995b), this indicates

that Ethiopians are at least just as slender as Kenyan Nandis.

The BMIs of several groups of boys of diﬀerent ethnic origin are in sharp contrast

to the BMIs of the Nandi boys. Thus, the BMIs of Nigerians (Ibu et al. 1986),

Libyans (Mukhtar et al. 1989), US blacks, whites and Hispanic (Rosner 1998),

Mexican–Americans (Zavaleta and Malina 1980) and Greenlanders (Becker-

Christensen 2002) are 4–5 kg m

2

(20–25%) higher compared to the BMIs of the

Nandi boys. It is of note that international results in long-distance running produced

by these people today are very scarce.

The fact that the proportion of leg length to total height changes only marginally

beyond the age of 16 years (Hertel et al. 1995) allows us to compare the percentage of

leg length to stature between the Kenyan boys and Caucasian adults. By subtracting

the distance from the ground to the middle of the lateral malleolus from the leg

length of the Kenyan boys, a direct comparison of leg length between these boys

and Caucasian elite runners described by Svedenhag and Sjo

¨din (1994) becomes

possible. This comparison reveals that the relative leg length of the Nandi town

and village boys is considerably longer compared to the Caucasian elite runners

Figure 2. BMIs of Nandi town and village boys and of adolescent boys of diﬀerent ethnic origin.

and

refer to two diﬀerent investigations of the same people presented in table 7.

Physical characteristics of Kenyan Nandi boys 167

(55.2 and 55.5 vs 52.8%). In addition, the relative leg length of the Nandi boys is

very consistent with ﬁndings on Kenyan elite runners (H. B. Larsen et al., unpub-

lished observation). Furthermore, the relatively long legs of the Nandis is in line

with earlier ﬁndings in a study comparing tibial length between six diﬀerent ethnic

minorities of East African origin and Caucasians (Allbrook 1961). This study

revealed that four of these groups had longer tibial length in absolute terms than

the Caucasians despite the fact that their stature was smaller. In addition, the rela-

tive tibial length was longer in the remaining two African groups compared to

Caucasians. Furthermore, the relatively long legs of the Nandi boys is in line with

ﬁndings in a study of 15-year-old African boys and adults from a large variety of

African countries (Meredith 1979) as well as ﬁndings in a study comparing 15-year-

old black American boys with white American boys (Spurgeon and Meredith 1979).

These investigations have shown a longer lower limb length relative to sitting height

(skelic index) of blacks compared to Caucasian boys (table 8). Additionally, as

the sitting height relative to height seems to be greater in Japanese (Ali et al. 2000),

Thai (Wacharasindhu et al. 2002), and Greenlanders (Becker-Christensen 2002)

boys compared to Caucasian boys (Hertel et al. 1995, table 8), this implies that the

relative leg length of the Nandi boys is considerably longer compared to these groups

of boys. In contrast, however, as many studies of adult Australian aborigines

have shown a very low sitting height relative to total height (Norgan 1994, table 8),

Table 8. Summary table of studies examining sitting height relative to height, skelic index (leg

length relative to sitting height) and leg length (distance from the middle of the lateral malleolus

to the anterior superior iliac spine) relative to height in adolescent boys and adults of diﬀerent

ethnic origin.

Study Subject population n

Age

(years)

Sitting height/

height ratio

Skelic

index

Leg length/

height ratio

Ali et al. 2000 Japanese 17 0.534

Pathmanathan and

Prakash 1994

Indian 20 15.8 0.515

Wacharasindhu et al.

2002

Thai 53 16.6 0.527

Hertel et al. 1995 Danish 16.5 0.520

Becker-Christensen 2002 Greenlanders 16 16.9 0.531

Norgan 1994, review

based on 17 diﬀerent

investigations

(1937–1977)

Australian aborigines 917 adults 0.488

Spurgeon and Meredith

1979

US whites 186 15 0.524 91.1

US blacks 219 15 0.506 97.7

Meredith 1979, review,

three studies

Black Africans >75 15 96–105

Five studies US blacks >290 15 98–101

Three studies US blacks 146 17 98–99

14 studies Black Africans 3223 adults 94–115

Two studies US blacks 987 adults 94–99

Svedenhag and Sjo

¨din

1994

Swedish elite runners 26 23.4 0.528

Present study Kenyan Nandi

town boys

11 16.6 0.552

Kenyan Nandi

village boys

19 16.6 0.555

168 H. B. Larsen et al.

this indicates that these people have similar or even longer relative leg length

compared to the Nandis.

Finally, as the study by Spurgeon and Meredith (1979) demonstrated that

the 15-year-old black American as well as Caucasian boys, who were considerably

shorter and lighter than Caucasian boys (Andersen 1994) of almost the same age

as the Nandi boys, had calf circumferences of 33.5 and 34.0 cm, respectively, this

indicates that the Nandi boys (calf circumference of 31.9 cm, table 1) have more

slender limbs in absolute terms compared to black American and Caucasian boys

of the same age.

Since the boys in this study volunteered for the investigation it may be speculated

whether they constitute a representative sample of Nandi boys. However, when

comparing the boys in the present study with an equally large sample of randomly

recruited Nandi boys and boys from other Kalenjin tribes (H. B. Larsen et al.,

unpublished observation) no diﬀerences were observed with respect to height,

weight, BMI or leg length.

4.1. Running economy (table 4)

The running economy of the two groups of Kenyan boys seems to be better than

what has been observed previously in untrained Caucasian boys of the same age,

irrespective of whether the oxygen cost is expressed per kilogram or per 0.75 kg

of body mass (A

˚strand 1952, Sjo

¨din and Svedenhag 1992). This indicates that the

superior running economy of the Nandi boys is due to inherent factors. Accordingly,

genetic factors may also partially or fully explain the previously observed superior

running economy of Kenyan world elite runners compared to Caucasian elite run-

ners (Saltin et al. 1995b). In addition, the fact that no diﬀerence in running economy

was observed between Nandi town and village boys indicates that the higher physical

activity level of the village boys during secondary school has limited or no eﬀect on

running economy.

4.2. Maximal oxygen uptake and physical activity level (tables 2,5 and 6,

ﬁgure 1)

The maximal oxygen consumption of the Nandi town boys is in line with previous

ﬁndings on untrained Kenyan boys from the same town (Saltin et al. 1995b), and

also similar to VO

2max

of untrained Caucasian boys (Andersen et al. 1987). However,

it can be argued that the maximal oxygen uptake of the town boys is higher com-

pared to untrained Caucasian boys due to the fact that the VO

2max

of the town boys

is reduced because they were tested at altitude. If measured at sea level, the VO

2max

of these boys would probably have been 3–5% higher (Favier et al. 1995). However,

if the VO

2max

of the Kenyan town boys is adjusted to sea level by adding 3–5% and

thus tends to be higher than VO

2max

of untrained Caucasian boys, this diﬀerence

is equalized when normalizing the data for diﬀerences in body mass (by using mass

to an exponent of 0.75 instead of 1, since the mass of the Nandi boys is about 12 kg

less than the mass of Caucasian boys of the same age (table 7)). ‘Scaling’ is used

in this relationship because it has proven useful in order to compare humans with

diﬀerences in body mass. Here 0.75 has been chosen, because Svedenhag (1995), who

has been studying adolescent runners, their VO

2max

and their running economy,

preferred to use this exponent. The maximal oxygen uptake of the Nandi village

boys was about 10% higher than the VO

2max

of the town boys, which may be due

to the higher physical activity level of the village boys. It is diﬃcult to interpret

Physical characteristics of Kenyan Nandi boys 169

the information concerning the physical activity level during childhood given by the

subjects based on interviews, because no information is available about the duration

or intensity of the diﬀerent kinds of physical activity (table 5). However, based on

the interviews, there is no indication of a diﬀerent physical activity pattern between

the two groups of boys until they began their secondary school education. After

starting secondary school, the habitual physical activity level of the village boys was

signiﬁcantly higher compared to the town boys. The question is therefore whether

the diﬀerence in physical activity can explain the observed diﬀerence in VO

2max

.It

is true that the duration of the physical activity of the village boys is consider-

ably longer compared to the town boys, but the intensity of the main part of this

activity may be much too low to stimulate VO

2max

for subjects consuming

50–55 mL kg

1

min

1

of oxygen maximally, since the ‘training threshold’ for these

subjects probably is an exercise intensity demanding a heart rate in the range of 135–

145 b.p.m (Larsen 2001). The 24-h heart rate recordings support this assumption,

even though these data must be interpreted with caution due to the low number of

recordings (ﬁgure 1). Thus, these recordings indicate that the duration of the period

during which the heart rate is above the necessary level needed to stimulate VO

2max

only 10–15 min day

1

. However, although not generally agreed (Milesis et al. 1976),

it has been demonstrated previously (Davies and Knibbs 1971) that only a 10-min

diﬀerence in the duration of short (10 min vs 20 min) daily exercise sessions (5 days

per week) can induce a diﬀerent increase in the VO

2max

in previously untrained

subjects. Therefore, taking both the questionnaires and the heart-rate recordings

into consideration, the observed higher VO

2max

of the village boys compared to

the town boys may be due to the higher physical activity level of the village boys.

This view gets support when studying the relationship between the time spent daily

doing sports and VO

2max

. While no correlation was found for the town boys, a trend

for a relationship was observed for the village boys (R¼0.52, p<0.07). When pool-

ing the data from both groups of boys a moderate correlation was found (R¼0.55,

p<0.01). Somewhat surprisingly, none of the boys in the two groups did much

running between home and school, partially because the main distance was short,

but also because that those who were running reported that they were only doing so

when they wanted to avoid being late for school. The most distinct diﬀerence in the

activity pattern between the village and the town boys was expressed through the

games of football and volleyball as well as working in the ﬁeld after school time

and during the weekends. Even though the maximal oxygen uptake of the village

boys was somewhat higher than the VO

2max

of the town boys, it is much lower than

the level reported previously for Kenyan junior runners who had a level of

64 mL kg

1

min

1

(Saltin et al. 1995b). This means that the daily physical activity

of the boys in the rural area does not give suﬃcient physiological stimulus in order to

reach the level needed to become an elite runner. However, some of the observed

diﬀerence in VO

2max

between the village boys in the present study and the junior

runners studied by Saltin et al. (1995b) is probably due to the fact that the junior

runners were selected.

The observed values of haemoglobin for both groups of Nandi boys are very low

when taking the altitude into consideration. This is probably due to the fact that all

village boys (n¼12) and half of the town boys (n¼4) who were studied with respect

to malaria reported that they had suﬀered from this disease.

This investigation demonstrated that the principal features with respect to body

dimensions of adolescent Kenyan Nandi town and village boys compares well with

170 H. B. Larsen et al.

ﬁndings in Kenyan elite runners. Thus, the Nandi boys have a very low BMI and

thus a slender body shape with relatively long and slender legs. In addition, the

study indicated that the oxygen cost when running is lower in untrained Kenyans

compared to untrained Caucasians and that this may be due to inherent factors.

Furthermore, the study demonstrated that Nandi boys from a rural area have a

higher capacity with respect to some physiological properties needed to become an

elite runner compared to Nandi town boys. Moreover, the study indicated that the

physical activity level of Nandi village boys is higher during secondary school com-

pared to Nandi town boys, which probably explains the observed higher maximal

oxygen uptake of the village boys.

Acknowledgements

The authors are grateful to all participating boys and their parents. We thank

Christian Borch for performing interviews and NIKE Danmark and Johnny Nielsen

for supplying all subjects with running shoes and sports equipment. The study was

supported by grants from TEAM DANMARK Research Foundation and the

Danish Ministry of Culture.

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cmrc.dk

Zusammenfassung. Das Ziel dieser Studie war die Charakterisierung von untrainierten Nandi Knaben

aus einer Stadt (n ¼11) und einer la

¨ndlichen Gegend (n ¼19) im Alter von 16,6 Jahren aus Westkenia

(Ho

¨he 2000 Meter u

¨ber Meeresspiegel) hinsichtlich Ko

¨rpermaße, Sauerstoﬀaufnahme und sportlicher

Aktivita

¨t. Die Knaben aus der Stadt hatten eine maximale Sauerstoﬀaufnahme (Vo

2max

) von 50 (45–

60) ml kg min

1

,wa

¨hrend die Dorfknaben einen Wert (Vo

2max

) von 55 (37–63) ml kg min

1

(P <

0,01) aufwiesen. Die Laufo

¨konomie, gemessen am Sauerstoﬀbedarf bei vorgegebener

Laufgeschwindigkeit, war fu

¨r Stadt- und Dorfknaben jeweils 221 ml kg

1

(597 ml kg

0.75

km

1

172 H. B. Larsen et al.

1

). Der Ko

¨rpermasse-Index (body mass index, BMI) war sowohl bei den Stadt- als auch bei den

Dorfknaben sehr niedrig (18,6 bzw. 18,4 kg m

2

). Wa

¨hrend der Schulzeit verbrachten Dorfknaben im

Mittel pro Tag signiﬁkant mehr Zeit bei Arbeiten auf dem Feld und beim Sport im Freien als Stadtknaben

(44,2 (0-128) gegenu

¨ber 1,3 (0-11) min, P<0,01 und 32,0 (11-72) gegenu

¨ber 12,8 (0-35) min, P<0,01). Es

wurde eine positive Korrelation zwischen der Zeit, die ta

¨glich beim Sport verbracht wurde, und Vo

2max

gefunden, wenn die Daten von Stadt- und Dorfknaben gemeinsam betrachtet wurden (R¼0.55, P<0.01).

Zusammenfassend wird festgestellt, dass die Ko

¨rpermaße jugendlicher Nandi Knaben aus sta

¨dtischem und

¨ndlichem Umfeld gut mit Befunden u

¨bereinstimmen, die bei Kenianischen Elite-La

¨ufern erhoben wur-

den. Sie sind sehr mager und haben relativ lange Beine. Daru

¨ber hinaus ist die Vo

2max

von Dorfknaben

¨her als die von Stadtknaben, was vermutlich auf die gro

¨ßere sportliche Beta

¨tigung wa

¨hrend der

Schulzeit zuru

¨ckzufu

¨hren ist.

´sume

´.Cette e

´tude a pour but de caracte

´riser des garc¸ ons Nandi citadins (n ¼11) et ruraux (n ¼19) non

entraıˆ ne

´setaˆ ge

´s de 16,6 ans, de l’ouest du Kenya (altitude 2000m) par rapport a

`leurs dimensions

corporelles, leur consommation d’oxyge

`ne et le niveau de leur activite

´physique. Les garc¸ ons citadins

ont une moyenne de consommation d’oxyge

`ne maximale (Vo

2max

) de 50 (45-60) ml kg min

1

alors que

les ruraux atteignent une valeur de 55 (37-63) ml kg min

1

(P<0,01). L’e

´conomie de course de

´termine

´e

comme le cou

ˆt d’oxyge

`ne lors d’une course a

`vitesse donne

´e, est de 221 ml kg

1

km

1

(597 ml kg

0,75

km

1

) aussi bien pour les citadins que pour les ruraux. L’indice de masse corporelle

(IMC) est tre

`s bas chez les citadins comme chez les ruraux (respectivement 18,6 et 18,4 kg m

2

). Le

temps passe

´en moyenne a

`des travaux a

`l’exte

´rieur et a

`des activite

´s sportives dans le cadre de l’e

´cole

secondaire, est signiﬁcativement plus e

´leve

´chez les ruraux que chez les urbains (respectivement (44,2 (0-

128) contre 1.3 (0-11) min, P<0.01 et 32,0 (11-72) contre 12.8 (0-35) min, P<0.01 ). Apre

`s regroupement

des donne

´es des deux e

´chantillons, on trouve une corre

´lation positive entre le temps passe

´quotidienne-

ment en activite

´sportive et le Vo

2max

(R ¼0,55 P<0.01). On conclut que les dimensions corporelles des

adolescents citadins et ruraux Nandi correspondent bien aux caracte

´ristiques des coureurs d’e

´lite du

´nya. Ils sont tre

`s minces avec des jambes relativement longues. De surcroıˆ t, le Vo

2max

des garc¸ ons

ruraux est plus e

´leve

´que celui de leurs homologues citadins, ce qui est probablement l’expression d’un

niveau d’activite

´physique plus e

´leve

´chez les ruraux dans le cadre de l’e

´cole secondaire.

Resumen. El objetivo de este estudio fue caracterizar a muchachos Nandi no entrenados, de 16,6 an

˜os de

edad, procedentes de una ciudad (n=11) y de un a

´rea rural (n=19) del oeste de Kenya (altitud 2000

metros sobre el nivel del mar), con respecto a sus dimensiones corporales, consumo de oxı

´geno y nivel de

actividad fı

´sica. Los chicos de ciudad tuvieron una consumo medio ma

´ximo de oxı

´geno (Vo

2max

)de50

(45–60) ml kg min

1

, mientras que los de la aldea alcanzaron un valor de 55 (37–63) ml kgmin

1

(P <

0,01) en Vo

2max

. La economı

´a de carrera determinada como el coste de oxı

´geno a una velocidad de carrera

dada fue de 221 ml kg

1

km

1

(597 ml kg

0,75

km

1

), tanto para los chicos de ciudad como para los

rurales. El ı

´ndice de masa corporal (IMC) fue muy bajo tanto en los chicos de ciudad como en los de la

aldea (18,6 vs. 18,4 kg m

2

). El tiempo medio diario dedicado a trabajar en el campo y a hacer deporte

durante la educacio

´n secundaria fue signiﬁcativamente mayor en los chicos del a

´rea rural que en los de la

ciudad (44,2 (0–128) vs. 1,3 (0–11) minutos, P<0,01 y 32,0 (11–72) vs. 12,8 (0–35) minutos, P<0,01,

respectivamente). Se encontro

´una correlacio

´n positiva entre el tiempo empleado diariamente en hacer

deporte y el Vo

2max

cuando se agrupaban los datos de los chicos urbanos y rurales (R=0,55, P<0,01). Se

concluye que las dimensiones corporales de los adolescentes Nandi de ciudad y de aldea se corresponden

con los resultados obtenidos en los corredores kenianos de elite, muy delgados y con las piernas relativa-

mente largas. Adema

´s, el Vo

2max

de los chicos rurales es mayor que el de los urbanos, lo que es debido,

probablemente, a un mayor nivel de actividad fı

´sica de los chicos rurales durante la educacio

´n secundaria.

Physical characteristics of Kenyan Nandi boys 173

Why the dominance of East Africans in distance running? A narrative review

Article

Full-text available

Aug 2024

Introduction Runners from East Africa including Kenya, Ethiopia and Uganda have dominated middle- and long-distance running events, for almost six decades. This narrative review examines and updates current understanding of the factors explaining the dominance of East Africans in distance running from a holistic perspective. Content The dominance of East African distance runners has puzzled researchers, with various factors proposed to explain their unparalleled success. Four key elements emerge: 1) biomechanical and physiological attributes, 2) training characteristics, 3) psychological motivations, and 4) African diet. Runners from East Africa often exhibit ectomorphic somatotypes, characterized by lean body compositions which lead them to an extraordinary biomechanical and metabolic efficiency. Their sociocultural lifestyle, training regimens beginning at a young age with aerobic activities, seem crucial, as well as moderate volume, high-intensity workouts at altitudes ranging from 2,000 to 3,000 m. Psychological factors, including a strong motivation to succeed driven by aspirations for socioeconomic improvement and a rich tradition of running excellence, also contribute significantly. A multifactorial explanation considering these factors, without a clear genetic influence, is nowadays the strongest argument to explain the East African phenomenon. Summary and outlook To unravel the mystery behind the supremacy of East African runners, it is imperative to consider these multifaceted factors. The predominantly rural lifestyle of the East African population underscores the importance of aligning modern lifestyles with the evolutionary past of Homo sapiens, where physical activity was integral to daily life. Further research is required to explain this phenomenon, with a focus on genetics.

Non-South East Asians have a better running economy and different anthropometrics and biomechanics than South East Asians

Article

Full-text available

Apr 2022

Running biomechanics and ethnicity can influence running economy (RE), which is a critical factor of running performance. Our aim was to compare RE of South East Asian (SEA) and non-South East Asian (non-SEA) runners at several endurance running speeds (10–14 km/h) matched for on-road racing performance and sex. Secondly, we explored anthropometric characteristics and relationships between RE and anthropometric and biomechanical variables. SEA were 6% less economical (p = 0.04) than non-SEA. SEA were lighter and shorter than non-SEA, and had lower body mass indexes and leg lengths (p ≤ 0.01). In terms of biomechanics, a higher prevalence of forefoot strikers in SEA than non-SEA was seen at each speed tested (p ≤ 0.04). Furthermore, SEA had a significantly higher step frequency (p = 0.02), shorter contact time (p = 0.04), smaller footstrike angle (p < 0.001), and less knee extension at toe-off (p = 0.03) than non-SEA. Amongst these variables, only mass was positively correlated to RE for both SEA (12 km/h) and non-SEA (all speeds); step frequency, negatively correlated to RE for both SEA (10 km/h) and non-SEA (12 km/h); and contact time, positively correlated to RE for SEA (12 km/h). Despite the observed anthropometric and biomechanical differences between cohorts, these data were limited in underpinning the observed RE differences at a group level. This exploratory study provides preliminary indications of potential differences between SEA and non-SEA runners warranting further consideration. Altogether, these findings suggest caution when generalizing from non-SEA running studies to SEA runners.

Muscle‐tendon architecture in Kenyans and Japanese: Potential role of genetic endowment in the success of elite Kenyan endurance runners

Article

Full-text available

Apr 2022

Aim: The specificity of muscle-tendon and foot architecture of elite Kenyan middle- and long-distance runners has been found to contribute to their superior running performance. To investigate the respective influence of genetic endowment and training on these characteristics, we compared leg and foot segmental lengths as well as muscle-tendon architecture of Kenyans and Japanese males (i) from infancy to adulthood and (ii) non-athletes vs. elite runners. Methods: The 676 participants were divided according to their nationality (Kenyans and Japanese), age (nine different age groups for non-athletes) and performance level in middle- and long-distance races (non-athlete, non-elite and elite adult runners). Shank and Achilles tendon (AT) lengths, medial gastrocnemius (MG) fascicle length, pennation angle and muscle thickness, AT moment arm (MAAT ) and foot lever ratio were measured. Results: Above 8 years old, Kenyans had a longer shank and AT, shorter fascicle, greater pennation angle, thinner MG muscle as well as longer MAAT , with lower foot lever ratio than age-matched Japanese. Among adults of different performance levels and independently of the performance level, Kenyans had longer shank, AT and MAAT , thinner MG muscle thickness and lower foot lever ratio than Japanese. The decrease in MG fascicle length and increase pennation angle observed for the adult Japanese with the increase in performance level resulted in a lack of difference between elite Kenyans and Japanese. Conclusion: The specificity of muscle-tendon and foot architecture of elite Kenyan runners could result from genetic endowment and contribute to the dominance of Kenyans in middle- and long-distance races.

Is the muscle-tendon architecture of non-athletic Kenyans different from that of Japanese and French males?

Article

Full-text available

Jun 2023
J Physiol Anthropol

Background: In endurance running, elite Kenyan runners are characterized by longer thigh, shank, and Achilles tendon (AT) lengths combined with shorter fascicles and larger medial gastrocnemius (MG) pennation angles than elite Japanese runners. These muscle-tendon characteristics may contribute to the running performance of Kenyans. Furthermore, these specific lower-leg musculoskeletal architectures have been confirmed not only in elite Kenyan runners but also in non-athletic Kenyans since early childhood. However, it remains questionable whether the differences in muscle-tendon architecture between Kenyans and Japanese differ from those of European Caucasians. Therefore, this study aimed to compare anthropometry and muscle-tendon architecture of young non-athletic Kenyan males with their Japanese and French counterparts. Methods: A total of 235 young non-athletic males, aged 17-22 years, volunteered. The anthropometric measures, thigh, and shank lengths, as well as AT and MG muscle architecture, were measured using ultrasonography and a tape measure. Inter-group differences in anthropometry and muscle-tendon architecture were tested using one-way ANOVA and ANCOVA analyses controlling for shank length and muscle thickness. Results: The anthropometric and muscle-tendon characteristics of the non-athletic French were closer to those of the Kenyans than to those of the Japanese. However, the ultrasonography analysis confirmed that the non-athletic Kenyans had the longest AT as well as the shortest MG fascicles and the largest pennation angle compared to the French and Japanese, even after controlling for shank length and muscle thickness with ANCOVA, respectively. Conclusions: These results confirmed the specificity of the muscle-tendon architecture of the triceps surae in Kenyans in comparison to their Japanese and French counterparts in non-athletic adults. This study provides additional support to the fact that Kenyans may have musculotendinous advantages in endurance running.

The Physiological and Morphological Characteristics of a Kenyan World-Class Long-Distance Runner: A Case Study

Article

Full-text available

May 2023

The purpose of this study was to compare the physiological and morphological characteristics of J. Ndambiri, a Kenyan world-class long-distance runner (10,000 m personal best: 27:04.79), with runners belonging to the national corporate team (29:32.18±0:30.35). Oxygen uptake (VO2), heart rate, blood lactate concentration and stride frequency were measured during submaximal exercise on a treadmill (270, 290, 310, 330, 350 and 370 m/min velocities with 1% inclination). Peak oxygen uptake (VO2peak) was determined during the maximal exercise test. In addition, morphological parameters (length of thigh and shank, maximum circumference of thigh and shank, and cross-sectional area of the trunk, thigh and shank muscles) were determined using a tape measure and magnetic resonance imaging (MRI). Ndambiri was superior to Japanese runners in terms of not only running economy (65.0 vs 69.8 ±1.9 ml/kg/min at 330 m/min), but also blood lactate concentration (1.50 vs 2.59±0.74 mmol/l at 330 m/min), heart rate (159.8 vs 170.8±4.0 bpm at 330 m/min) during the submaximal running test and VO2peak (80.8 vs 76.3±2.4 ml/kg/min). In addition, the morphological characteristics of Ndambiri were also quite different from those of Japanese runners. In particular, Ndambiri's maximum shank circumference was much smaller than that of Japanese runners (32.0 vs 35.8±1.8 cm). Furthermore, the cross-sectional area of the gastrocnemius muscle, which composes the shank, was significantly correlated with the oxygen cost of running at 330 m/min (r＝0.700). These findings indicate that the superior performance of Ndambiri is attributable to various factors such as a higher VO2peak, lower blood lactate concentration and heart rate, as well as running economy. In the future, it will be necessary to clarify the factors supporting these relationships between physiological variables and morphological characteristics.

Born high, born fast: Does highland birth confer a pulmonary advantage for sea level endurance?

Article

Full-text available

Nov 2024
EXP PHYSIOL

Less than 7% of the world's population live at an altitude above 1500 m. Yet, as many as 67% of medalists in the 2020 men's and women's Olympic marathon, and 100% of medalists in the 2020 men's and women's Olympic 5000 m track race may have been born or raised above this otherwise rare threshold. As a possible explanation, research spanning nearly a quarter of a century demonstrates that indigenous highlanders exhibit pulmonary adaptations distinct from their lowland counterparts. These adaptations may then promote endurance performance. Indeed, healthy indigenous highlanders often exhibit a larger aerobic exercise capacity compared to sea‐level residents who travel to high altitude. However, questions remain on whether high‐altitude birth is advantageous for sea‐level competitions. In this review, we ask whether being born at a high altitude generates an ergogenic advantage for endurance performance in the Summer Olympics—a venue that is generally held at sea level. In so doing, we distinguish between three groups of high‐altitude residents: (i) the indigenous highlander, (ii) the highland newcomer, and (iii) the highland sojourner. Concentrating specifically on altitude‐induced alterations to pulmonary physiology beginning in the perinatal period, we propose that if altitude‐related maladaptations are avoided, genomic and developmental alterations accompanying highland birth may present benefits for endurance competitions at sea level.

Analysis of over 1 million race records shows runners from East African countries as the fastest in 50-km ultra-marathons

Article

Full-text available

Apr 2024

The 50-km ultra-marathon is a popular race distance, slightly longer than the classic marathon distance. However, little is known about the country of affiliation and age of the fastest 50-km ultra-marathon runners and where the fastest races are typically held. Therefore, this study aimed to investigate a large dataset of race records for the 50-km distance race to identify the country of affiliation and the age of the fastest runners as well as the locations of the fastest races. A total of 1,398,845 50-km race records (men, n = 1,026,546; women, n = 372,299) were analyzed using both descriptive statistics and advanced regression techniques. This study revealed significant trends in the performance of 50-km ultra-marathoners. The fastest 50-km runners came from African countries, while the fastest races were found to occur in Europe and the Middle East. Runners from Ethiopia, Lesotho, Malawi, and Kenya were the fastest in this race distance. The fastest 50-km racecourses, providing ideal conditions for faster race times, are in Europe (Luxembourg, Belarus, and Lithuania) and the Middle East (Qatar and Jordan). Surprisingly, the fastest ultra-marathoners in the 50-km distance were found to fall into the age group of 20–24 years, challenging the conventional belief that peak ultra-marathon performance comes in older age groups. These findings contribute to a better understanding of the performance models in 50-km ultra-marathons and can serve as valuable insights for runners, coaches, and race organizers in optimizing training strategies and racecourse selection.

Chapter 1 - Physiology of endurance running in Blagrove, R and Hayes, P The Science and practice of middle and long distance running, https://doi.org/10.4324/9781003088912. This is the accepted version but not in the same format as it appears in the book.

Chapter

Full-text available

Nov 2023

Highlights • Middle and long distance running events are determined by a complex mix of factors • The highest rate of energy production that can be maintained for the race duration and the ability to convert that into movement determine middle and long-distance performance • The aerobic system is the main energy system used in middle and long distance running • The anaerobic system is important for middle-distance race and coping with changes of pace within a race • Appropriate training can improve all of the factors that determine middle and long distance performance

How do differences in Achilles’ tendon moment arm lengths affect muscle-tendon dynamics and energy cost during running?

Article

Full-text available

Apr 2023

Introduction The relationship between the Achilles tendon moment arm length (ATMA) and the energy cost of running (Erun) has been disputed. Some studies suggest a short ATMA reduces Erun while others claim a long ATMA reduces Erun. For a given ankle joint moment, a short ATMA permits a higher tendon strain energy storage, whereas a long ATMA reduces muscle fascicle force and muscle energy cost but shortening velocity is increased, elevating the metabolic cost. These are all conflicting mechanisms to reduce Erun, since AT energy storage comes at a metabolic cost. Neither of these proposed mechanisms have been examined together. Methods We measured ATMA using the tendon travel method in 17 males and 3 females (24 ± 3 years, 75 ± 11 kg, 177 ± 7 cm). They ran on a motorized treadmill for 10 min at 2.5 m · s⁻¹ while Erun was measured. AT strain energy storage, muscle lengths, velocities and muscle energy cost were calculated during time-normalized stance from force and ultrasound data. A short (SHORT n = 11, ATMA = 29.5 ± 2.0 mm) and long (LONG, n = 9, ATMA = 36.6 ± 2.5 mm) ATMA group was considered based on a bimodal distribution of measured ATMA. Results Mean Erun was 4.9 ± 0.4 J · kg⁻¹ · m⁻¹. The relationship between ATMA and Erun was not significant (r² = 0.13, p = 0.12). Maximum AT force during stance was significantly lower in LONG (5,819 ± 1,202 N) compared to SHORT (6,990 ± 920 N, p = 0.028). Neither AT stretch nor AT strain energy storage was different between groups (mean difference: 0.3 ± 1 J · step⁻¹, p = 0.84). Fascicle force was significantly higher in SHORT (508 ± 93 N) compared to LONG (468 ± 84 N. p = 0.02). Fascicle lengths and velocities were similar between groups (p > 0.72). Muscle energy cost was significantly lower in LONG (0.028 ± 0.08 J · kg · step⁻¹) compared to SHORT (0.045 ± 0.14 J · kg · step⁻¹ p = 0.004). There was a significant negative relationship between ATMA and total muscle energy cost relative to body mass across the stance phase (r = −0.699, p < 0.001). Discussion Together these results suggest that a LONG ATMA serves to potentially reduce Erun by reducing the muscle energy cost of the plantarflexors during stance. The relative importance of AT energy storage and return in reducing Erun should be re-considered.

Measurement and reporting of footwear characteristics in running biomechanics: A systematic search and narrative synthesis of contemporary research methods

Article

Oct 2022

This review aimed to synthesise the methods for assessing and reporting footwear characteristics among studies evaluating the effect of footwear on running biomechanics. Electronic searches of Scopus®, EBSCO, PubMed®, ScienceDirect®, and Web of Science® were performed to identify original research articles of the effect of running footwear on running biomechanics published from 1st January 2015 to 7th October 2020. Risk of bias among included studies was not assessed. Results were presented via narrative synthesis. Eligible studies compared the effect of two or more footwear conditions in adult runners on a biomechanical parameter. Eighty-seven articles were included and data from 242 individual footwear were extracted. Predominantly, studies reported footwear taxonomy (i.e., classification) and manufacturer information, however omitted detail regarding the technical specifications of running footwear and did not use validated footwear reporting tools. There is inconsistency among contemporary studies in the methods by which footwear characteristics are assessed and reported. These findings point towards a need for consensus regarding the reporting of these characteristics within biomechanical studies to facilitate the conduct of systematic reviews and meta-analyses pertaining to the effect of running footwear on running biomechanics.

Relationships of marathon running to physiological, anthropometric and training indices

Article

Full-text available

Aug 1983
Eur J Appl Physiol Occup Physiol

This study was aimed at investigating the relationships between marathon performance time (MPT) and a set of variables wider in scope than that used to date in similar studies. Sixteen marathon runners of varying abilities were examined for the following variables prior to the start of a marathon race: age, weight (wt); height (ht); triceps, abdominal and subscapular (SSF) skinfolds; % fat; rectal temperature; average weekly training distance over the preceding 2–3 months and over the preceding year (ATD); hematocrit; creatine phosphokinase (CPK); aldosterone and cortisol. MPT's ranged between 2; 15:21 and 4; 54:31 h. The coefficients of the simple linear correlations with MPT were: age, 0.70; wtht–2, 0.57; SSF, 0.67; % fat, 0.61; ATD, –0,64; CPK, 0.52 and cortisol, –0.41. In order of relative strength, CPK, age, ATD, SSF and cortisol were found by a multiple linear regression analysis to be the best predictors of MPT (R=0.99; p<0.0001) — explaning 98% of its observed variance. The diversified approach may be supported by the high R value obtained. However, the significance of additional factors in determining MPT is expected and cannot be excluded.

Nível de atividade física em adolescentes do Município de Niterói, Rio de Janeiro, Brasil

Article

Full-text available

Dec 2000

O presente estudo teve como objetivo investigar o nível de atividade física (AF) de adolescentes de Niterói, Rio de Janeiro. Alunos (n = 325) da rede pública de ensino tiveram seus AF avaliados pelo questionário de Crocker et al. (1997), PAQ-C. Dados antropométricos (massa corporal, estatura e índice de massa corporal) e horas que assistem à televisão (TV) também foram coletados. As médias dos escores do PAQ-C foram 2,3 e 2,0 para meninos e meninas, respectivamente (p < 0,01). A média de TV foi de 4,4 e 4,9 horas/dia para os sexos masculino e feminino. As atividades físicas mais praticadas foram o futebol entre os meninos e a caminhada entre as meninas. Os adolescentes apresentaram maior nível de atividade nos finais de semana em comparação aos dias de semana. Os valores do PAQ-C classificaram 85% dos meninos e 94% das meninas como sedentários. Os resultados encontrados alertam para a alta prevalência de sedentarismo neste grupo, aumentando a probabilidade de adultos sedentários. No entanto, outros estudos devem ser desenvolvidos para determinação de AF durante toda a adolescência e dos fatores determinantes da atividade física regular.

Maximal exercise performance in chronic hypoxia and acute normoxia in high-altitude natives

Article

May 1995

Maximal O2 uptake (VO2max) was determined on a bicycle ergometer in chronic hypoxia (CH) and during acute exposure to normoxia (AN) in 50 healthy young men who were born and had lived at 3,600 m altitude (La Paz, Bolivia). VO2max was significantly improved (approximately 8%) by AN. However, the difference in VO2max measured in CH and AN (delta VO2max) was lower than that reported in sea-level natives (SN) who exercised in chronic normoxia and acute hypoxia. It is shown that high-altitude natives (HN) and SN have a similar VO2max in normoxia, but highlanders can attain a greater VO2max when O2 availability is reduced by altitude exposure. In addition, in HN, the higher the subject's VO2max in hypoxia, the smaller his delta VO2max. These results contrast with the data obtained in 14 lowlanders acclimatized to high altitude who showed that their delta VO2max was positively related to their VO2max in hypoxia, as previously reported in SN who exercised in acute hypoxia (A. J. Young, A. Cymerman, and R. L. Burse. Eur. J. Appl. Physiol. Occup. Physiol. 54: 12–15, 1985). Furthermore, arterial O2 saturation of HN behaved differently from acclimatized lowland natives, inasmuch as it fell less during exercise both in CH and AN. HN with high aerobic capacity display a lower exercise ventilation and a reduced arterial saturation, which could explain their inability to improve VO2max with normoxia.(ABSTRACT TRUNCATED AT 250 WORDS)

Frictional and kinetic factors in the work of sprint running

Article

Jan 1930
Am J Physiol

W.O. Fenn

Nonparametric Statistics For The Behavioral Sciences

Article

Jan 1956

S. S. Siegel

The training stimulus

Article

Dec 1971
Eur J Appl Physiol Occup Physiol

The effects of various regimes of bicycle ergometer exercise varying in intensity, duration and frequency of effort on directly measured maximum aerobic power (

\dot V_{O_2 }

max) have been studied on 28 healthy male subjects aged 18–38 years. Analysis of the results showed that the two most important factors in training the

\dot V_{O_2 }

max were intensity and duration; these parameters being interdependent. No subject who trained at or below 50% of

\dot V_{O_2 }

max showed an improvement in his maximum aerobic power output. Even at the highest intensities and longest durations of effort the improvement in

\dot V_{O_2 }

max was quite small (1–9 ml/kg/min). The responses to submaximal work mirrored in part these changes:

\dot V_{O_2 }

and

\dot V_E

for a given work load remained constant whereas cardiac frequency (fH) decreased after training. It would seem that in order to effect an improvement in

\dot V_{O_2 }

max an individual must be prepared to work at or close to his maximum for prolonged periods of time; even then the improvement may be disappointingly small.

Non-Parametric Statistics for The Behavioral Sciences

Chapter

Jan 1956

S. Siegel Castellan

The abstract for this document is available on CSA Illumina.To view the Abstract, click the Abstract button above the document title.

Percentiles for body mass index in U.S. children 5 to 17 years of age

Article

Feb 1998
J Pediatr

It has been recommended that body mass index (BMI) (weight in kilograms/height in meter2) be used routinely to evaluate obesity in children and adolescents. This report describes the distribution of BMI in children and adolescents in the United States. Standardized measurements of height and weight from 9 large epidemiologic studies including 66,772 children age 5 to 17 years were used to develop tables for the distributions of BMI that are age, race, and gender specific. The mean BMI increases with age and is slightly higher for girls than boys. Mean BMI for black and Hispanic girls was noticeably higher than for white girls. The percentiles of BMI are consistently higher than those based on the NHANES I measures, particularly for the 95th percentile. The proportion of obese children compared with NHANES I standards is higher and is highest for Hispanic boys and black and Hispanic girls. The tables and figures will allow pediatricians to determine the relative ranking of BMI for patients compared with values derived from a large sample of healthy children and adolescents. The identified gender and ethnic differences may be guides to understanding the cause and prevention of obesity.

Relationship of lower limb height to sitting height in Black populations of Africa and the United States

Article

Jul 1979

Howard V. Meredith

This article examines a recently reported generalization. Materials from more than a score of invetigations are drawn upon. These materials show there is not a substantial research base for the claim that interbreeding in the United States between black people of African ancestry and white people of European ancestry has resulted in increased lower limb height relative to sitting height.

Body size and form of Black and White male youths: South Carolina youths compared with youths measured at earlier times and other places

Article

Jun 1979

From original data at age 15 years on 405 United States Black and White males residing in Richland County, South Carolina, statistics are presented for 10 somatic variables. The two ethnic groups, measured during 1974-1977, yield similar means for arm girth, calf girth, and body weight; the Black youths, compared with their white age peers, are shorter in sitting height, longer in lower limb height, narrower in hip width, longer in lower limb height relative to sitting height, and narrower in hip width relative to lower limb height. The South Carolina groups are compared with Black and White youths studied in the United States near 1900, and with Black and White youths studied during the last 25 years in Africa, Australia, Canada, Europe, Lesser Antilles, South America, and the United States.

Body dimensions, exercise capacity and physical activity level of adolescent Nandi boys in western Kenya

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