Study Oct. 1945

Effects of Ultraviolet Radiation on Physical Fitness

by Robert M. Allen, A.B. and Thomas K. Cureton, Ph.D. Urbana, IL
Reprinted from the Archives of Physical Medicine,
October 1945, Volume XXVI, pp. 641-644.

This study on the effect of ultraviolet radiation on physical fitness was done at the University of Illinois. The ten-week controlled study compared men on a five item muscular endurance test and on the Schneider cardiovascular fitness index. The twenty-two subjects were from the lower third of basic physical fitness classes.

• The experimental group gained 19.2% on the Schneider cardiovascular index compared to 1.5% for the control group.
  
• The experimental group gained 15.4% in motor fitness compared to the 11.8% for the control group.
  
• The experimental group had ten colds compared to twenty for the control group.
  

An experiment was planned to determine whether the motor and cardiovascular fitness of a group of college freshmen would be affected by regularly scheduled doses of ultraviolet rays. The rays have previously been reported to have remedial effects in preventing the occurrence of upper respiratory tract infection. Ultraviolet rays give rise to vitamin D, promote normal calcium anabolism and stimulate a larger retention of phosphorous. Radiation has been shown to influence dietary inadequacies and to rectify partial lack of the components necessary for proper calcification of bones and teeth. Lorand stated that as an example of the sterilizing effect the cities of Lyons and Paris have exposed quantities of water to ultraviolet rays for sterilization purposes. He further stated that calcium, phosphorous and vitamins are increased in the system after exposure to ultraviolet rays. While such effects have been claimed, the present experiment is perhaps the first to test the effect of ultraviolet rays on motor and cardiovascular fitness. No previous studies on these aspects have appeared in the literature of health and physical education or any other known source.

Method of Research

It was planned to compare an experimental group of 11 men with a control group of 11 men, all selected from classes in basic physical fitness. The basic physical fitness classes consisted of men classified in the lower third of motor endurance by the five item muscular endurance test. Equalization of control and experimental groups was secured by the times on the mile run. All subjects were required to run a mile for time. The times were tabulated from the best to the poorest, and selection of the two parallel groups was made by alternate selections from a rank order list of these times. The experimental group averaged 6:46 on the mile and the control group 6:47. On the day of the run the trainers were unaware that this method was to be used; therefore, there was no tendency to select the more able students as candidates for ultraviolet irradiation.

After the experiment was begun the experimental group reported three times per week for the sun treatment in addition to physical education. The control group took the same physical education but did not take the irradiation. The treatments were taken in the nude, and the time was increased from one minute the first four weeks for one and one-half minutes the following four weeks and finally to ten minutes the last two weeks. Exposure to ultraviolet was the only known difference in the programs of the two groups during the ten weeks of the experiment, Nov. 14, 1944 to Jan. 21, 1945. No classes were held outside; therefore, the class was not in the natural sun during any physical education period.

On Oct. 19, 1944 both groups were required to participate in the five item muscular endurance test. On Jan. 23, 1945 the final retest was given with the same test. On Oct. 21, 1944 all trainees were given a Schneider test and a Schneider index rating. The final ratings were given on Jan 20, 1945. From these test results comparisons were made to show how the experimental group improved in motor fitness (five item test) and cardiovascular fitness (Schneider index) as compared with the control group. At the end of the experiment a questionnaire consisting of five questions was answered by the members of the experimental group to test their reactions to the ultraviolet ray treatment.

The retest reliability on the Schneider test is 0.86; the mile run is 0.81 and the five item muscular endurance test is about 0.93.

Results

Comparisons of the initial and final Schneider tests resulted in a 19.2 per cent standard score gain by the experimental group as compared with a 1.5 per cent standard score gain by the control group. By comparing the initial scores in the muscular endurance fitness tests with the final scores in these tests, it was observed that the experimental group showed a 15.4 percent and the control group an 11.8 per cent standard score gain.

The number of colds contracted by members of the control group was twenty, as compared with ten colds contracted by the members of the experimental group.

The experimental results are shown in table 1 and the significant differences for each item in table 2. [Note: In the interests of brevity, table 2 has been omitted here. Its results are summarized in conclusions 3 and 4. Contact Light for Health for this and more information.]

Table 1. - Improvements in Cardiovascular Fitness

* For the gains to be considered reliable according to the statistical tests for significance: (a) the gains in the Schneider test must give a computed t greater than 2.97 (experimental) and 2.97 (control); (b) the gains in the five item muscular endurance test must give a computed t greater than 2.86 (experimental) and 3.16 (control) according to the F table for small samples. (Davenport, C. H., and Ekos, Merle P.: Statistical Methods in Biology, Medicine and Psychology, New York, John Wiley & Sons, Inc., 1936, pp. 38 and 180-1).
† One subject failed to complete the tests.

The results of the questionnaire are shown in the following tabulation.
Only ten boys completed the questionnaire, one having been called to military service.

Describe exactly what effect the light has had on you.
Answers below.

1. "I think the light has kept me from feeling tired during my long hours of study at night. I have felt more wide awake during the day since I had the ultraviolet treatment."
   
2. "I have had fewer colds this winter. My skin is a shade darker."
   
3. "Judging from the usual amount of colds I experience during the early winter months, I am sure that the light has been an important factor in the general condition of my health."
   
4. "During the winter I usually have a continuous severe cold. Since I have been taking the ultraviolet the colds have been lighter and less frequent."
   
5. "I think the light has decreased my susceptibility to colds. I also think that it has increased my supply of energy."
   
6. "I was too inconsistent in attendance for the light to have any effect on me."
   
7. "I think the light has been a great help to me. I know definitely that I have not had as many colds this winter as I did last winter even though I am now living in a colder climate."
   
8. "Started to give me a tan. I don't think it prevented me from getting a cold because I never have had many in the past."
   
9. "I think the light warms me up for a while and makes me better in P. E. class following it than if I had not had it. It also gives us a fairly good sun tan. It probably helped me in general."
   
10. "I have had fewer colds during the period of experimentation than I usually have during a similar period of time."

Conclusions

1. The ultraviolet light produced a 19.2 per cent standard score gain in the Schneider index for the experimental group as compared with 1.5 per cent gain for the control group, which took the same physical training but did not take the irradiation. The gain for the experimental group meets the test of significance for a small sample, whereas the gain for the control group does not meet this test.
   
2. The ultraviolet light produced a 15.4 per cent standard score gain in the Illinois five item muscular endurance test for the experimental group, as compared with an 11.8 per cent gain for the control group. The gains meet the significant test for small samples.
   
3. An analysis of the significance of the difference between the means of the initial and final tests in each item shows that there are shifts of near significance in (1) pulse rate change, lying to standing: (2) pulse rate after exercise; (3) change in pulse rate, standing to post exercise, and (4) time for pulse rate to recuperate to standing pulse rate after the standard exercise. In the pulse rate changes the differences were more significant for the experimental group and were all in the direction, which suggests improved condition due to the ultraviolet irradiation.
   
4. The differences reach near significance in systolic blood pressure, lying and standing, where the changes in the means show a trend toward lowered systolic blood pressure due to exercise and also to the irradiation. Such changes need to be explored more fully with older subjects with relatively high blood pressure.
   
5. The experimental group showed greater interest in class work, attended more regularly and unanimously voted to continue the irradiation if permitted to do so.
   
6. The experiment should be continued and repeated with another group in a similar manner for an independent check.

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