Human Movement Science 2 (1983) 151-159

North-Holland

151

ON THE ORIGIN OF DIFFERENCES IN PERFORMANCE LEVEL BETWEEN ELITE MALE AND FEMALE SPEED SKATERS

G.J. van INGEN SCHENAU and G. de GROOT *

Free University and University of Amsterdam, The Netherlands

Ingen Schenau, G.J. van and G. de Groot, 1983. On the origin of differences in performance level between elite male and female speed skaters. Human Movement Science 2. 15 l- 159.

The skating technique expressed in skating position, stroke frequency, amount of work per stroke and external power of five elite males was compared with the technique of ten elite females. The

main difference between both groups appeared to be a difference in skating position. The female

and the male group showed almost the same external power per kilogram body weight during

skating.

It is concluded that the difference in performance level between both groups is mainly caused

by a difference in skating position and in friction and not by a difference in work capacity as one

might expect on the basis of the lean body masses of both groups. The influence of the higher

percentage of fat in the female group on the skating position and on a difference in frictional losses

is discussed.

Introduction

The performance level of elite female speed skaters has strongly in- creased in the last decades. A comparison of world records shows that differences between male and female elite speed skaters have been reduced from over 30% in the early thirties to 6-9% nowadays. A reason for this reduction might be that in contradistinction to the past, the present female skaters have the same training background with respect to intensity, number of training sessions per week and number of years in training as the male skaters. In a recent study (Ingen Schenau and de Groot in press) it was shown that during supramaximal

* Mailing address: G.J. van Ingen Schenau, Dept. of Functional Anatomy, IFLO, P.O. Box 7161,

1081 BT Amsterdam, The Netherlands.

0167-9475/83/$3.00 0 1983, Elsevier Science Publishers B.V. (North-Holland)

152 G.J. onn Ingen Schenau, G. de Groat/Male and female speed skating

cycling, female speed skaters delivered the same external power PC per kilogram body weight (PJBW) as male speed skaters despite the fact that the female group had a 20% lower mean maximal oxygen con- sumption ( VO/BW) than the male group.

Since, during skating, the power losses to air friction will be a function of the third power of the speed, the difference in external power ( Pf) during skating is supposed to be much larger than the 6-9% difference in world record times. This would, however - in the light of the equal P,/BW as was measured during cycling - be surprising. When, on the other hand, elite female speed skaters deliver the same external power P,/BW during skating as elite males, the differences in speed must be caused by differences in skating technique or in fric- tional losses which, in turn, could be influenced by skating position or body weight.

The purpose of this study was to investigate the nature of the difference in performance level of elite male and female speed skaters. This has become of interest since the results of the bicycle tests mentioned above, showed that elite females have the same capacity to deliver external power (relative to body mass) as elite males.

Methods

Subjects

From the participants of the world championships 1982 for all-round female speed skaters in Inzel (800 m altitude, German Federal Repub- lic), ten skaters were, on the basis of their previous achievements,

pre-selected for analyses of their technique. These 10 subjects actually obtained places one to nine and the eleventh place in the final classifi- cations of that championship. The skaters were filmed (16mm; 25 frames/s) during the 500m, 1500m and 3000m races from outside the track and perpendicular to it, at a distance of about 30m.

The data from these films could be compared with data from five elite male speed skaters collected during the Golden Skate competition in 1980 at the same location (Ingen Schenau et al. 1983). The weather and ice conditions during both these competitions in Inzel were good, the wind velocity being negligible. The possible influence of develop- ments in physical condition and technique of the male group in the two

G.J. oan Ingen Schennu, G. de Groat/Male and female speed skating 153

Fig. 1. The skating position. The pre-extension knee angle is equal to SO = O2 + 0,.

years between 1980 and 1982 is regarded as not relevant for this study since the improvements in personal records since 1980 of the best male speed skaters on the three distances which were analysed are not appreciable.

Measurements

The methods used for obtaining the technical data have been described earlier (Ingen Schenau and Bakker 1980; Ingen Schenau et al. 1983; Ingen Schenau 1982). The angles which determine the skating position (fig. 1) were analysed with the help of a motion analyser. For each lap the external power Pr was calculated as a function of pre-extension knee angle 0,( = 0, + e3; fig. l), position of the trunk (8,; fig. 1) and speed during each lap, at given body mass and body length. The amount of work per stroke (A) was calculated from external power and stroke frequency ( f) according to A = P,/f. If more than one individ- ual set of data per distance was obtained, the average value was calculated.

It must be emphasised that all technical data are applicable to the situations of full laps only, assuming a uniform velocity during each lap. The influence of the start (particularly important for the 500m race) on final times is not, therefore, incorporated.

Statistics

Differences between the groups were tested for significance using t-statistics. The significance level was taken at p < 0.05; two tailed. It

154 G.J. van Ingen Schenau, G. de Groat/Male and female speed skating

must be emphasised that the fact that the groups are rather small makes it difficult to generalise differences found to other populations of speed skaters.

Results

Mean values and standard deviations of the angles which determine the skating position (fig. l), stroke frequency f, amount of work per stroke (A); external power ( Pr) and speed (v) are presented in table 1. The most striking differences in technique which hold for all distances appear to be connected with a difference in pre-extension knee angle (~9,) which mainly originates from the difference in the position of the thigh (8,). In the position of the trunk, no differences between the groups could be shown.

Discussion

The trunk position is horizontal when the angle 8i between the line between the hip joint (great trochantor) and the middle of the neck and the horizontal is about 15” (fig. 1). From wind-tunnel experiments it was concluded that a horizontal trunk is the most optimal position with respect to air friction (Ingen Schenau 1982). Table 1 shows that in this respect no difference exists between the male and female group. At the 1500m and 3000m distances, the subjects of both groups held their trunk nearly optimal while at the 500m distance, both groups expe- rienced some waste of energy due to their non-horizontal trunk posi- tion.

In previous studies it was suggested that a small pre-extension knee angle (8,) is an important requisite for successful speed skating (Ingen Schenau and Bakker 1980; Ingen Schenau et al. 1983). Table 1 shows that the female group differs strongly from the male group in this respect (about 1 lo). Particularly the difference in 0, is striking. The values of t$ and 0, of the elite females are equal to those found in non-elite male skaters (Ingen Schenau et al. 1983). Particularly at the 500m distance this larger 0, of the female group will be the main reason for the lower amount of work per stroke and (given the equal stroke frequency) the lower power per kilogram body weight (table 1).

Tab

le

1

Tec

hnic

al

vari

able

s of

el

ite

mal

e (n

=

5) a

nd

fem

ale

(n

= 10

) sp

eed

skat

ers.

0,

0,

8,

00

f A

/BW

P

,/BW

1)

9

degr

ees

degr

ees

5 de

gree

s de

gree

s s-

’ J/

k W

att/k

g m

/s

ii 5o

om

Mal

es

23.4

29

.1

75.7

10

5.4

2.10

2.

95

6.22

13

.77

2 w

SD

5.4

5.0

4.8

1.6

0.03

0.

24

0.53

0.

19

2

Fem

ales

18

.1

51.0

66

.8

177.

8 2.

10

2.69

5.

65

13.0

3 2

SD

4.1

3.0

4.6

4.7

0.09

0.

19

0.28

0.

23

$

Dif

f(%

) 23

-7

2 *

12 *

:

- 12

*

0 9*

9*

5*

F

15oo

m

9

Mal

es

17.1

47

.5

64.1

11

1.6

1.66

2.

88

4.78

12

.35

P

SD

1.9

3.3

3.0

? 6.

0 0.

07

0.10

0.

34

0.33

Fem

ales

16

.8

54.6

66

.9

0,

121.

5 1.

67

2.76

4.

60

11.8

6

SD

2.9

2.6

2.4

3.1

0.06

0.

17

0.22

0.

19

2 D

iff(

%)

2 -

15 *

-4

-9

* 0

4 4

4*

2 2 30

00m

s.

L

Mal

es

16.9

48

.7

64.1

11

2.8

1.51

2.

76

4.24

11

.94

3 S SD

2.

6 1.

3 2.

8 3.

8 0.

04

0.09

0.

25

0.23

3

Fem

ales

16

.2

56.8

67

.0

123.

8 1.

45

2.73

3.

95

11.0

2 B

SD

1.

6 2.

9 2.

8 3.

2 0.

07

0.23

0.

3 1

0.37

2

Dif

f(%

) 4

9 -1

6 *

-5

- 10

*

4*

1 7

8*

%

5.

Not

e:

8,,

0,,

0,

and

0,

( =

0, +

0,)

de

term

ine

the

skat

ing

posi

tion

(fig

. 1)

; f

is t

he

stro

ke

freq

uenc

y an

d A

th

e am

ount

of

w

ork

per

stro

ke;

P,

equa

ls

the

@?

exte

rnal

po

wer

pe

r ki

logr

am

body

w

eigh

t, o

is t

he

mea

n sp

eed

duri

ng

the

full

laps

.

Dif

fere

nces

ar

e ex

pres

sed

as p

erce

ntag

e of

th

e va

lues

of

th

e m

ales

.

* Si

gnif

ican

t di

ffer

ence

(p

c

0.05

, tw

o ta

iled)

.

t; m

156 G.J. van Ingen Schenau, G. de Groor/Male and female speed skatrng

A second disadvantage of the higher 0, of the female group is the fact that at the same speed the amount of loss to air friction increases with increasing 0,. From the model presented previously (Ingen Schenau 1982) it can be calculated that the decrease in speed during the 3000 m race due to the 1 lo higher B0 (table 1) is about 3.3%. Almost half of the difference in speed between the groups would, therefore, disappear if the female skaters were able to skate at the same pre-extension knee angles as the males. For the 1500m the difference in speed would decrease to only 1.2% and for the 500m to 2.3% at equal pre-extension knee angles. These calculations are only true when the speed remains constant during the race. Nevertheless, it seems obvious to advise the females to skate at smaller 0, and 0, angles. The question arises to what extent one might expect the females to skate at the same 0, and 0, values as the males.

If it is assumed that the 10 subjects of the present study have the same 20% of fat as that found in five elite Dutch speed skaters (Ingen Schenau and de Groot, in press), this percentage of fat could be a reason for the higher 8, values of the females, since the elite males showed ‘a much lower percentage of about 10% (Ingen Schenau et al. 1983). At the same skating position, the same amount of work per stroke and total body weight, a higher amount of fat and thus a lower lean body mass will be coupled to higher muscle forces per kilogram muscle tissue both during the gliding phase as well as during the push-off phase. With the help of the model of stroke mechanics presented previously (Ingen Schenau and Bakker 1980), it can be calculated that this difference in fat could explain about 20% of the difference in 0, at the 500m and about 50% of the difference in 0, at the 1500m and 3000m races when it is assumed that both groups can maintain the same muscle force relative to their lean body mass. It is not clear to what extent the difference in fat really might prevent the females from skating at lower 6’, values. From the mentioned compari- son of elite males and females during cycling, it was concluded that the females showed the same power (and the same force at equal pedalling rate) per kilogram total body weight. Moreover Wilmore (1974) re- ported a higher leg strength in females when compared to males when this strength is taken relative to lean body weight.

During the 500m and 1500m the females show the same stroke frequency as the males while during the 3000m the females have a 4% lower stroke frequency. This last difference might be connected to the

G.J. oan Ingen Schenau, G. de Groat/Male and female speed skating 157

fact that women rarely skate long distances. One can speculate that when more attention is paid to longer distances (which probably will be the case after the introduction in 1983 of the 5000m as an official race in the female all-round championships) that the performance on this 3000m distance will strongly increase, particularly as a result of higher stroke frequencies.

The females showed a lower external power at all distances although, only at on the 500m was this difference statistically significant. At the 500m distance, the lower external power appears to be caused by lower work per stroke values which are, as mentioned previously, strongly coupled to the pre-extension knee angles 8,.

If it is assumed that the females in the present study have the same 20% fat as the five Dutch females of the previous study (the males were the same in both studies), it can be calculated that the females have a power output per kilogram lean body weight during skating of respec- tively 7.06, 5.75 and 4.93 W/kg at the three distances while the males with 10% fat show 6.91, 5.31 and 4.71 W/kg (LBM) respectively. These data conform the conclusion of the previous study (Ingen Schenau and de Groot in press.) that the differences in performance level between male and female speed skaters cannot be explained by a lower power output per kilogram muscle mass. On the contrary: the elite women appear to deliver more power than would be expected from their lean body mass.

The difference in performance level

It is not a matter of course that subjects with a high power output per kg LBM will in principle also be good performers. Apart from technical influences (trunk position, pre-extension knee angle) it cannot be excluded that performance is more a function of, for example, total power output or power output per kilogram total body weight. More- over if the anaerobic and aerobic capacity of subjects shows a stronger increase as a function of body weight than the increase of frictional loss, heavy subjects will have an advantage over light subjects. For speed skating this problem can be clarified with the help of the model of total frictional loss as a function of body weight, body length, speed Biand 0, (Ingen Schenau 1982). The actual mean body masses and mean body lengths of both groups of this study are taken as starting points.

158 G.J. oan Ingen Schenau, G. de Groat/Male and female speed skating

At a knee angle of 0, = 112” and horizontal trunk position, the females (mass: 66 kg, length: 1.71 m) need 370 Watt to maintain a speed of 13.5 m/s (500m level). At the same 0, and 8, the males (mass: 73 kg, length: 1.81 m) need 406 Watt to maintain the same speed. When expressed per kilogram body weight, the females and the males have to deliver 5.6 W/kg. At the same 6, at 0, = 115” and at a speed of 11.5 m/s (3000m level) the values are also equal (3.9 W/kg) for both females and males. Based on these predictions from the model it can be concluded that external power per kilogram total body mass is a reliable measure for performance in this sport. There seems to exist no dependence on differences in body build as long as the maximal external power is strictly proportional to body weight. With respect to sex differences it is concluded that women will actually need a higher power output per kilogram lean body mass than men for maintaining the same speed if they have a higher percentage of fat than the men. Since the position in speed skating is comparable with the position of the limbs in cycle racing and since the ice friction and the rolling resistance in cycling are both proportional to body weight (Whitt and Wilson 1974; Faria and Cavanagh 1’978), it seems likely that, with respect to performance, the external power during cycling (as can be measured during bicycle ergometry) should be expressed in Watts per kilogram total body mass.

In conclusion it can be stated that the difference in performance level between elite male and female speed skaters is mainly due to dif- ferences in skating position and percentage of body fat and not to a difference in work capacity.

From this study it is not possible to predict to what extent the elite females would be capable (wholly or partly) of overcoming differences. What can be predicted with help of the model of total friction is that, given the same total external power during skating of both groups, the women could come up to the performance level of the men if they could maintain at least the same knee angle and if they decreased their percentage of fat from 20% to a level below 16%. Further, it seems likely that a decrease in percentage of fat would facilitate a lower pre-extension knee angle.

G.J. uan Ingen Schenau, G. de Groat/Male and female speed skating 159

References

Farm, I.E. and D.R. Cavanagh, 1974. The physiology and biomechanics of cycling. New York:

Wiley. Ingen Schenau, G.J. van, 1982. The influence of air friction in speed skating. Journal of

Biomechanics 15, 449-458.

Ingen Schenau, G.J. van and K. Bakker, 1980. A biomechanical model of speed skating. Journal of

Human Movement Studies 6, l- 18.

Ingen Schenau, G.J. van and G. de Groat, in press. Differences in oxygen consumption and

external power between male and female speed skaters during supramaximal cycling. European

Journal of Applied Physiology.

Ingen Schenau, G.J. van, G. de Groot and A.P. Hollander, 1983. Some technical, physiological and

anthropometrical aspects of speed skating. European Journal of Applied Physiology 50,

343-354.

Whitt, F.R. and D.G. Wilson, 1974. Bicycling science. Cambridge, MA: The M.I.T. Press.

Wilmore, J.H., 1974. Alterations in strength, body compositions and anthropometric measure-

ments consequent to a lo-week weight training program. Medicine and Science in Sports 6:

133-138.