physical fitness of blind and sighted children

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Eur J Appl Physiol (1987) 56:69--73 European Journal of Applied hysiolo , and Occupational Physiology Springer-Verlag 1987 Physical fitness of blind and sighted children W. G. Hopkins, H. Gaeta, A. C. Thomas, and P. McN. Hill Department of Physiology, School of Medicine, University of Auckland, Private Bag, Auckland, New Zealand Summary. Twenty-seven children (age 7--17 years) with varying degrees of blindness but with no other known disorder were assessed for physi- cal fitness. Twenty-seven randomly selected chil- dren with normal eyesight, were also assessed. Maximum oxygen uptake (170 .... ) was measured directly during a progressive exercise test on a treadmill. There was a significant and substan- tial reduction in 12o .... in totally blind chil- dren (mean +- standard deviation 35.0+_7.5 ml. rain -1. kg -1) compared with normal chil- dren (45.9+_6.6 ml. min-1, kg-l). Partially sighted children had a significant but smaller re- duction in pro2.,,X. Fitness assessed by a step-test was significantly reduced in the visually impaired children, and skin-fold thickness was also signifi- cantly greater in totally blind children. The level of habitual physical activity for each child, as assessed by a questionnaire, correlated with l?o2m, ~ (r=0.53, p<0.0001). Blind children were significantly less active than normal chil- dren, and the difference between mean l)'o .... for blind and normal children became non-significant when their different activity levels were taken into account. It is concluded that totally blind children are less fit than other children at least partly be- cause of their lower level of habitual activity. Key words: Fitness -- Maximum oxygen uptake -- Activity -- Blindness Introduction There is a growing body of evidence that people who exercise regularly enjoy good health and Offprint requests to: W. G. Hopkins at the above address have a long life expectancy. The evidence is clear- est in relation to heart disease and obesity: a num- ber of studies have indicated a lower incidence of heart disease amongst active people (for example Paffenbarger et al. 1984; Chave et al. 1978), and inactivity has been recognised as a more impor- tant contributor to obesity than overeating (John- son et al. 1956). Regular exercise is also benefical in the management of diabetes (Bjorntorp and Krotkiewski 1985) and asthma (Henriksen et al. 1981; Svenonius et al. 1983). It seems reasonable to conclude that children whose level of physical activity is below normal could be disadvantaged from health point of view during childhood and later in life. Because of the limitations placed on their freedom of movement, blind children would be expected to be disadvantaged in this way. It was therefore of interest to subject blind and normal children to several standard "fitness" tests to determine whether there were any signifi- cant differences between the children related to degree of blindness. The most widely used index of fitness is the maximum oxygen uptake (l?O2m,x), which is defined as the maximum rate of con- sumption of oxygen that a subject can achieve while performing physical exercise. An individu- al's maximum oxygen uptake is probably confer- red to a large extent by heredity (Klissouras 1971), but it can be increased nevertheless by up to 30% by increased regular exercise (Astrand and Ro- dahl 1977). Consequently, the average level of maximum oxygen uptake in different groups of people may serve as an index of whether different levels of habitual exercise between these groups have a significant effect on the physiological sta- tus of individuals in the groups. In previous studies blind children have been shown to have significantly lower maximum oxy- gen uptakes or work capacities compared with

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Page 1: Physical fitness of blind and sighted children

Eur J Appl Physiol (1987) 56:69--73

European Journal of

Applied hysiolo ,

and Occupational Physiology �9 Springer-Verlag 1987

Physical fitness of blind and sighted children

W. G. Hopkins, H. Gaeta, A. C. Thomas, and P. McN. Hill

Department of Physiology, School of Medicine, University of Auckland, Private Bag, Auckland, New Zealand

Summary. Twenty-seven children (age 7--17 years) with varying degrees of blindness but with no other known disorder were assessed for physi- cal fitness. Twenty-seven randomly selected chil- dren with normal eyesight, were also assessed. Maximum oxygen uptake (170 . . . . ) was measured directly during a progressive exercise test on a treadmill. There was a significant and substan- tial reduction in 12o . . . . in totally blind chil- dren (mean +- standard deviation 35.0+_7.5 ml . rain -1 . kg -1) compared with normal chil- dren (45.9+_6.6 ml . m i n - 1 , kg- l ) . Partially sighted children had a significant but smaller re- duction in pro2.,, X. Fitness assessed by a step-test was significantly reduced in the visually impaired children, and skin-fold thickness was also signifi- cantly greater in totally blind children.

The level of habitual physical activity for each child, as assessed by a questionnaire, correlated with l?o2m, ~ (r=0.53, p<0.0001). Blind children were significantly less active than normal chil- dren, and the difference between mean l)'o . . . . for blind and normal children became non-significant when their different activity levels were taken into account. It is concluded that totally blind children are less fit than other children at least partly be- cause of their lower level of habitual activity.

Key words: Fitness -- Maximum oxygen uptake -- Activity - - Blindness

Introduction

There is a growing body of evidence that people who exercise regularly enjoy good health and

Offprint requests to: W. G. Hopkins at the above address

have a long life expectancy. The evidence is clear- est in relation to heart disease and obesity: a num- ber of studies have indicated a lower incidence of heart disease amongst active people (for example Paffenbarger et al. 1984; Chave et al. 1978), and inactivity has been recognised as a more impor- tant contributor to obesity than overeating (John- son et al. 1956). Regular exercise is also benefical in the management of diabetes (Bjorntorp and Krotkiewski 1985) and asthma (Henriksen et al. 1981; Svenonius et al. 1983). It seems reasonable to conclude that children whose level of physical activity is below normal could be disadvantaged from health point of view during childhood and later in life. Because of the limitations placed on their freedom of movement, blind children would be expected to be disadvantaged in this way.

It was therefore of interest to subject blind and normal children to several standard "fitness" tests to determine whether there were any signifi- cant differences between the children related to degree of blindness. The most widely used index of fitness is the maximum oxygen uptake (l?O2m,x), which is defined as the maximum rate of con- sumption of oxygen that a subject can achieve while performing physical exercise. An individu- al's maximum oxygen uptake is probably confer- red to a large extent by heredity (Klissouras 1971), but it can be increased nevertheless by up to 30% by increased regular exercise (Astrand and Ro- dahl 1977). Consequently, the average level of maximum oxygen uptake in different groups of people may serve as an index of whether different levels of habitual exercise between these groups have a significant effect on the physiological sta- tus of individuals in the groups.

In previous studies blind children have been shown to have significantly lower maximum oxy- gen uptakes or work capacities compared with

Page 2: Physical fitness of blind and sighted children

70 W . G . Hopkins et al.: Fitness of blind children

normal children (Cartmel and Banister 1969; Cumming et al. 1971; Sundberg 1982). However in all of these studies the testing was performed on bicycle ergometers, a mode of exercise unfam- iliar to most blind children. Since performance in an exercise test is influenced significantly by fa- miliarity with the mode of exercise (Astrand and Rodahl 1977), these studies have not resolved whether blind children are indeed significantly less fit than normal children.

We decided to test blind and normal children using a treadmill for the exercise test, since run- ning would be a more familiar form of exercise to the blind children than bicycling. We also used the Canadian Step Test (Shephard et al. 1976) on some of the children, since stair climbing is also a familiar activity for the blind. Standard anthro- pometric data and skinfold thickness were also re- corded together with the result of a test of abdom- inal strength and a test of torso flexibility. The children were questioned about their involvement in physical activities at school and at home, and an index of habitual physical activity was derived from the answers to these questions to determine whether the blind children were significantly less active than normal children.

Methods

2 - - No physical activity other than school physical educa- tion periods.

3 -- Walking or cycling to and from school, participation in school physical education, active play at school and at home.

4 -- As for 3, with participation in organised sport part of the year.

5 - - As for 4, but with participation in organised sports all year.

Anthropometr ic characteristics measured were height, weight and skinfold thickness. An obesity index was calcu- lated as weight - height -2. Skinfolds were measured with John Bull calipers at the triceps, biceps, subscapular and suprailiac sites; the median of three measurements at each of the sites was recorded, and the mean of the four medians was calcu- lated (Wilson and Russell 1985). Flexibility was measured us- ing a sit and reach test. Strength-endurance of the abdominal muscles was also tested with a partial sit-up test. The protocols for both of these tests were developed by the Biometrics Unit at the University of Otago, Dunedin, New Zealand (Wilson and Russell 1985).

Children at Intermediate or Secondary School (12--17 years of age) were then subjected to the Canadian Home Fit- ness stepping test (Shephard et al. 1976). Totally blind subjects needed the guiding hand of an adult throughout the test in order to perform the stepping manoeuvre, so all subjects (in- cluding controls) were given the same assistance to ensure comparability of the results. Heart beats were counted at the appropriate times in the test by palpation of a carotid artery. Scores of 1--5 were awarded according to the heart rate at- tained following one, two or three 3-minute bouts of step- ping.

Finally the lko . . . . was assessed in all children with a pro- gressive exercise test on a motor-driven treadmill. For children 9 years of age or older the treadmill was started at 3 km - hr-1,

Subjects. The subjects were all the blind or partially sighted children attending school to the fourth form level (age range 7--17 years) in the Auckland urban area. The level of blind- ness had been assessed previously in all children and was ob- tained from parents or from records maintained by the Royal NZ Foundat ion for the Blind. The levels were B1 (totally blind), B2 (visual acuity up to 2/60 a n d / o r 5% of vision) and B3 (visual acuity between 2/60 and 6/60 a n d / o r 20% of vi- sion). Children with any additional physical or mental handi- cap or known disease were excluded. There were two totally blind children whose parents would not give consent for the testing. Altogether 27 blind or partially sighted children (13 males and 14 females) were tested, 20 of whom were Euro- peans and 7 Polynesians. Each visually handicapped child was matched with a normal child of the same sex and ethnic origin, chosen where possible from the same school and same class- room as the visually handicapped child. Where more than one normal child of the same sex and ethnic origin was available, the normal child whose surname was alphabetically closest to that of the visually handicapped child was chosen so as to eliminate any bias in the selection procedure. The normal and visually handicapped children were with few exceptions tested together as matched pairs.

Testing procedures. Personal data for each subject were ob- tained in a short interview. The level of habitual activity was assessed by questionnaire and an activity score of 1--5 was recorded as follows: 1 - - Very inactive at home, no participation in school physi-

cal education or school playtime activities.

Table 1. I2o . . . . , step test and activity scores, skinfold thick- ness and obesity for control and bl ind groups. Values shown are mean _+ standard deviation

Control B3 B2 B1

Number of children 27 9 7 11

l/o . . . . 45.9** 41.6 42.0 35.0 (ml �9 min -1 �9 kg -1) +6.6 +5.5 +6.7 +7.5

Step test a 3.7** 2.8 2.5 2.1 +1.1 +0.5 +0.6 +0.4

Activity 3.7** 3.3 2.4 2.1 +0.5 +0.5 +0.8 +1.1

Skinfolds 4.4 4.7 4.6 8.0* (mm) _+1.6 +_1.9 + _ 1 . 1 +_4.4

Obesity 18.7 19.6 18.0 21.0 (kg. m -~) +2.3 _+3.2 _+3.5 _+3.4

Fewer children underwent the step test: 15 control, 4 B3, 4 B2 and 7 B1

** Significantly greater than mean for bl ind groups (p < 0.001)

* Significantly greater than means for control, B3 or B2 (p <0.01)

Page 3: Physical fitness of blind and sighted children

W. G. Hopkins et al. : Fitness of blind children

Table 2. Matrix of significant coefficients of correlation between variables

71

Vo . . . . Activity Step Test Skinfolds Obesity

Blindness - 0.52 - 0.68 - 0.65 0.44 n.s. (p < 0.001) (p < 0.0001) (p < 0.0001) (p < 0.002)

lko . . . . 0.53 0.58 - 0.31 - 0.43 (p < 0.001) (p < 0.0006) (p < 0.03) (t7 < 0.002)

Activity 0.45 - 0.41 n.s. (p < 0.02) (p < 0.005)

Skinfolds n.s. 1 0.49 (p<O.O01)

n.s. = not significant (p �9 0.05)

0% inclination, and the speed was increased by 2 km - hr -a ev- ery 2 rain until 9 km. hr -~ was reached. Subjects were in- structed to jog at 7 and 9 km �9 h r - ~. After 2 rain at 9 km �9 h r - the inclination was increased by 3% every 2 rain and verbal encouragement was given until the subject was exhausted. For children 8 years of age or younger a similar protocol was used, the four speeds being 2.4, 4, 5 and 6 km �9 hr -~. Subjects were instructed to jog at 5 and 6 km �9 hr-~. Two of the younger sub- jects who did not reach exhaustion on their protocol at an an- gle of 24% were retested at a later date using the procotol for the older children.

Respiratory variables were measured using an open system. Subjects breathed through a mouthpiece with a two way Koe- gel valve with deadspace approx 100 ml. Inspired volumes were measured with a pneumotachograph. Oxygen and carbon dioxide concentrations in the expired gas were measured con- tinuously using a Servomex 02 analyser and a Beckman LB2 CO2 analyser after the gas passed through a mixing chamber. Oxygen uptake was calculated approximately every 20 sec- onds by a microcomputer interfaced with the pneumotachom- eter and gas analysers. The system was calibrated daily with a calibration gas which had been analysed independently in a Haldane apparatus.

The electrocardiogram was monitored during each exer- cise test on the treadmill, and heart rate was recorded by the computer. A plateau in the heart rate and obvious signs of ex- haustion in the subject were the criteria for deciding that l)o . . . . had been achieved. This did not occur in four subjects (one B1, one B2 and two B3), and for these children graphs of oxygen uptake against heart rate were plotted, and the best straight line through the points drawn by eye was extrapolated to the mean maximum heart rate efa l l the other subjects of the same age in order to estimate the Vo ..... .

Statistical analysis. One way analysis of variance was used to compare mean values for different variables for the different blindness groups and for different activity levels. Post-hoc multiple comparisons were made using a general linear model to fit means.

Results

Table 1 summarises the mean values for the varia- bles measured in the three blindness groups and in the control groups of children, while Table 2 summarises the significant linear correlations be- tween variables. A greater degree of visual handi- cap was associated significantly with reduced

1)o . . . . , reduced activity, reduced score on the step test and greater skinfold thickness. There was a slight but non-significant positive correlation between blindness and obesity index. 12o . . . . was higher with greater level of activity, higher with greater step test score, lower with greater skinfold thickness and lower with greater obesity. The more active children had higher step test scores and thinner skinfolds, although a negative corre- lation between activity and obesity did not reach statistical significance. Not shown in the tables are the data for flexibility and abdominal strength-endurance, which did not correlate sig- nificantly with blindness, 12 o . . . . , activity, skin- fold thickness or obesity. The only variable show- ing a significant difference between males and fe- males was Vo2max in the control group (mean _+ standard deviation: males 50.2_+5.5, females 41.9+_4.8 ml . min -1 . kg-1; p<0.001) and in the combined blind group (males 41.6 _+6.9; females 36.6+_7.0 ml - ra in -~ �9 kg_~; p < 0.05).

The mean values of Vo . . . . for each blindness level are depicted graphically in Fig. 1. Also shown in the figure are the mean values following an analysis of covariance that adjusted the means

7_s "

~ 40 -

35 -

i

l con t ro l B3 B2 B1

l eve l o f blindness

Fig. 1. Mean 12 o . . . . in the blindness and control groups ( O - - O ) . Also shown are means adjusted for activity covar- iance ( � 9 -O) . Bars represent standard error of means

Page 4: Physical fitness of blind and sighted children

72 W. G. Hopkins et al.: Fitness of bl ind chi ldren

5O-

E 45-

4 0 " C~

0

3 5 -

// 4 5

i 1 2 3

level of activity

Fig. 2. Mean 12o . . . . at each level o f activity. Bars represent s tandard error o f mean. Only one child had an activity score o f 5

to take into account the difference in I>o . . . . that accompanies the different levels of activity in the blindness and control groups. The differences be- tween these adjusted means no longer reach sta- tistical significance (f=2.18, p>0.05). The clear p.ositive correlation between level of activity and Vo . . . . for all subjects combined is shown in Fig. 2.

Discussion

This study has revealed a clear difference in the average level of physical fitness of partially sighted and totally blind children in comparison with normal children. Several earlier studies re- ported similar results when bicycle ergometers were used to test the subjects, whereas we have used a treadmill and a step test. Therefore the dif- ferences we have observed between the blind and normal children cannot be ascribed solely to poor performance by subjects unfamiliar with the mode of exercise used in the test.

The differences in the oxygen uptakes are con- siderable. Totally blind children have a mean oxy- gen uptake which is 24% less that that of the nor- mal children. The standard deviation for the nor- mal children is 14%, so it is clear that totally blind children are well outside the normal range of val- ues for normally sighted children. The means for the two groups of partially sighted children are only 9% less than that for the controls, and while these are statistically significant, the values are more within the range of those for normal chil- dren.

We observed also that skinfold thickness cor- relates significantly with degree of blindness, al- though in this case it is only the totally blind chil- dren who differ significantly from either the con- trol or the partially blind children. The weight, height -2 obesity index did not correlate significantly with blindness, although the totally blind children tend to have higher obesity scores. This may be a reflection of the unreliability of this particular index of obesity.

We have extended the previous studies by as- sessing each child's level of habitual activity and relating this to obesity, fitness and degree of blindness. Several important relationships emerge from these data:

Firstly, there is a significant negative correla- tion between skinfold thickness and physical ac- tivity, which is consistent with an earlier study of normal children (Mayr 1956). Thus children who are active are more likely to have a healthy body composition.

Secondly, there are good correlations between activity and l?O2max (r=0.53) or step test score (r----0.45). This is consistent with longitudinal studies showing increases in oxygen uptake with training in children (Rowland 1985), and also with the few cross-sectional studies of children re- lating fitness tests to activity. Kemper et al. (1975) found relatively weak correlations ( r= 0.21--0.35) between activity measured by questionnaire or pe- dometer and performance in 12 min run-walk or submaximal work load test in 12--13 year old school boys. More recently Atomi et al. (1986) monitored daily heart rates in 9--10 year old boys and observed a high correlation ( r= 0.74) between time spent at high heart rates (i. e. vigorous habi- tual activity) and 12o . . . . . A similar objective measure of activity in the present study would presumably result in an improvement in the corre- lations between activity and Vo . . . . or step test score.

Thirdly, our results show that the more visu- ally handicapped children are less active overall. It is therefore interesting to consider whether the visually handicapped children are less fit than normal simply because they are less active. Figure 1 shows that when allowance is made for the rela- tionship between activity and fitness, the visually handicapped children are no longer significantly less fit than normal. However, it can be seen in Fig. 1 that the totally blind children have an oxy- gen uptake that is still considerably less than that of the normal or partially blind children. Further testing of a greater number of children or with a more precise instrument to determine activity lev-

Page 5: Physical fitness of blind and sighted children

W. G. Hopkins et al.: Fitness of blind children 73

els is required to determine whether the totally blind are significantly less fit even when their lower levels of activity are taken into account. A longitudinal study involving extra physical educa- tion for the totally blind ow~r an extended period would be an alternative and more rewarding ap- proach to this problem. A similar approach with blind adults produced a significant elevation of gO2ma x (Siegel et al. 1970).

Acknowledgements. We are grateful to John Stratford of the Royal NZ Foundation for the Blind for advice and encourage- ment, and to Professor David Russell and his team from Otago University for advice on administering some of the tests. The New Zealand Medical Research Council provided financial support.

References

Astrand P-O, Rodahl K (1977) Textbook of work physiology. McGraw-Hill, New York

Atomi K, Iwaoka K, Hatta H, Miyashiti M, Yamamoto Y (1986) Daily physical activity levels in preadolescent boys related to Iio . . . . and lactate threshold. Eur J Appl Physiol 55:156--161

Bjorntorp P, Krotkiewski M (1985) Exercise treatment in dia- betes mellitus. Acta Med Scand 217:3--7

Cartmel JL, Banister EW (1969) The physical working capac- ity of blind and deaf school children. Can J Physiol Phar- macol 47:833--836

Chave SPW, Morris JN, Moss S, Semmence AM (1978) Vigor- ous exercise in leisure time and the death rate: a study of male civil servants. J Epidemiol Community Health 32:239--243

Cumming GtL Goulding D, Baggley G (1971) Working capac- ity of deaf, and visually and mentally handicapped chil- dren. Arch Dis Childhood 46:490--494

Henriksen JM, Toftegaard Nielsen T, Dahl R (1981) Effects of physical training on plasma citrate and exercise-induced asthma. Scand J Clin Lab Invest 41:225--229

Johnson ML, Burke BS, Mayer J (1956) Relative importance of inactivity and overeating in the energy balance of obese high school girls. Am J Clin Nutr 4:37--44

Kemper HCG, Verschuur R, Ras KGA, Snel J, Splinter PG, Tavecchio LWC (1975) Biological age and habitual activity in relation to physical fitness in 12--13 year old school- boys. Z KJnderheilk 119:169--179

Klissouras V (1971) Heritability and adaptive variation. J Appl Physiol 31:338--344

Mayer J (1956) Relation between calorie intake, body weight and physical work. Am J Clin Nutr 4:169--175

Paffenbarger RS, Hyde RT, Wing AL, Steinmetz CH (1984) A natural history of athleticism and cardiovascular health. J Am Med Assoc 252:491--495

Rowland TW (1985) Aerobic response to endurance training in prepubescent children: a critical analysis. Med Sci Sports Exer 17:493--497

Shephard RJ, Bailey DA, Mirwald RL (1976) Development of the Canadian Home Fitness Test. Cana Med Assoc J 114:675--679

Siegel W, Blomqvist G, Mitchell JH (1970) Effects of a quanti- tated physical training programme on middle-aged seden- tary men. Circulation 41 : 19--29

Sundberg S (1982) Maximal oxygen uptake in relation to age in blind and normal boys and girls. Acta Paediatr Scand 71:603--608

Svenonius E, Kautto R, Arborelius M (1983) Improvement after training of children with exercise-induced asthma. Acta Paediatr. Scand 72:23--30

Wilson PG, Russell DG (1985) The national fitness survey: the pilot study. NZ J Health Phys Ed Rec 18:15--22

Accepted October 7, 1986