THE JOURNAL OP APPLIED PSYCHOLOGY Vol. 38, No. 2, 1954
Effects of Fatigue and Anxiety on Certain Psychomotor and Visual Functions1
Sherman Ross, T. A. Hussman, and T. G. Andrews University of Maryland
This experiment was an attempt to investi- gate the degree of behavior decrement pro- duced by the experience of fatigue and threat of bodily damage occasioned in the competi- tive athletic sport of boxing. The dependent variables chosen as possible indicators of be- havior decrement were: (a) steadiness score; (b) body sway score; (c) body sway time score; (d) tapping rate; and (e) critical nicker frequency. The primary purpose of the experiment was to determine whether or not performance on each of the five depend- ent variables changes significantly as a result of intensive muscular exercise (fatigue) or the fear of bodily injury (anxiety) or the in- teraction of these conditions in the collegiate competitive boxing situation.
There has been some speculation in the past regarding the damaging effects on be- havior of sustained head blows such as re- ceived in continuous training in boxing (13), In addition to these interests in boxing, such a situation appears to offer a realistic condi- tion of systemic fatigue, high motivation, and anxiety such as could not be attained under the usual conditions of laboratory investiga- tions. These characteristics are not unlike those which obtain in certain field conditions of military operations and combat. In the general search for indicators of behavior dec- rement for military purposes, the use was made of boxing behavior to approximate these characteristics of military importance.
The basis for the selection of the indicators used in this investigation is described below for each of the five dependent variables to- gether with a description of the manner of testing.
1 This experiment is one of a series of studies on behavior decrement performed under Contract No. DA-49-007-MD-222 between the Medical Research and Development Board, Office of The Surgeon Gen- eral, Department of the Army and the University of Maryland. The opinions and assertions expressed in this report do not necessarily reflect the views of the Department of the Army.
Tests and Indicators Used Steadiness has been demonstrated to show
changes under certain conditions of stress, and it has been reported to change with fatigue or work output (1, 4, 5, 18). Hand steadiness and tremor have also been related to emotional stimu- lation (6, 7) and to certain conditions of motiva- tion (4). Because of these features, a test of hand steadiness was included among the depend- ent variables. For this test a target hole in a vertically adjustable metal plate was used. The subject’s task was to keep a 0.02 inch diameter stylus inserted into the 0.136 inch hole for 20 seconds with the arm fully extended and unsup- ported. The number of contacts with the edge of the hole during this period served as the score.
Body sway measurements have offered rather controversial results in the past when related to fatigue (11, 18) and to loss of sleep (5, 15), Because of the possible effects of head blows sustained in boxing, measures of body sway were obtained. For this purpose an arrangement simi- lar to that for steadiness was used. However, in this case the stylus was longer and the hole diameter was 0.358 inch. The subject was re- quired to hold the stylus in the hole, but in this case without the aid of visual cues. When con- tact was made with the edge of the hole, a buzzer was automatically sounded as a signal to the sub- ject. Two scores were derived from this test: a body sway score of the number of contacts made in the 20 second period, and a body sway time score consisting of the total amount of time in seconds the stylus was in contact with the edge of the hole during the observation pe- riod. These were treated as separate scores in the analysis of the data.
Tapping tests serve as measures of rather sim- ple performance, but have been considered by some investigators as useful indices of fatigue (IS, 16). Tapping has been shown to be re- lated to the decrement produced by high altitude (9), The tapping test apparatus used here con- sisted of the Dunlap modification of the Whipple Tapping Board (3) and a 0.20 inch diameter stylus. The tapping targets were two 3 inch square brass plates separated by 1 inch of bake- lite. The subject was to tap alternately on the plates as rapidly as possible for a period of IS seconds. The score used was. the total number of taps on the plates in this allotted time. This brief time period was. used as an attempt to di- minish the factor of learning, which has been shown to affect tapping scores (17).
120 S. Ross, T. A. Hussman, and T. G. Andrews
Critical Flicker Frequency has been used in several investigations on fatigue with contro- versial results (12, 14, 18). There has been some indication that CFF changes when the in- dividual is subjected to intensive strain (2). The apparatus used in the present study was the Krasno-Ivy Flicker Photometer (8), which is es- sentially an episcotister arrangement delivering square wave flashes, of light on a % inch ground glass screen. The subject was seated S feet from the stimulus screen. A modified method of lim- its was used, in which the experimenter manipu- lated the stimulus from “fusion to flicker” and the subject responded at his threshold. Six “descending” trials were employed, the first two serving as practice. The score or threshold measure was the mean number of flashes for the last four trials.
In each of the above tests only a brief period could be devoted to obtaining a score, since in many instances the subjects were being measured immediately after strenuous exercise and before they were covered, rubbed down, or bathed. Longer testing periods would have increased the reliabilities of the measures taken, but also- might possibly have allowed the injurious effects of chilling the subjects.
Twenty-four male college students ranging in age from 19 to 25 years were used as subjects. Twelve of the group were experienced collegiate boxers and members of the University of Mary- land Boxing Team for 1952. The remaining sub- jects were members of a Physical Education class in boxing and should be classed as novice boxers. All subjects were in excellent physical condition.
Independent Variables and Experimental Design
Each of the 24 subjects was measured three times on each of the tests under each of four conditions of the investigation. These four con- ditions were as follows:
a. At rest, no previous strenuous exercise, no expectation of going into the ring to fight.
b. Before fighting a three-round supervised bout, no previous exercise.
c. After three rounds of very strenuous work- out on a heavy punching bag, not in the ring nor expecting to go into the ring.
d. After fighting a three-round supervised bout with an opponent.
These four conditions yield a basic 2 X 2 block of the experimental design, which is diagrammed in Table 1. It may be seen that this arrange- ment opposes the no-exercise conditions (F-0) to the heavy exercise conditions (F) for a test of the change in each variable as a result of fatigue. The test of change in each variable due to the anxiety occurring in the boxing situation
is made by opposing the no-anxiety conditions (A-0) to the high anxiety conditions (A). The problem of fatigue in this arrangement is quite straightforward. The problem of anxiety, how- ever, offers some question. In this regard it may be said that all observations on and reports from the men immediately before and after such com- petitive boxing indicate severe tension and con- cern over the threat of pain and bodily damage or loss of the bout.
In order to minimize the effects of the order of taking the tests in the battery, each subject was randomly assigned to one of the 24 possible orders of test administration, which he main- tained throughout the experiment. Each subject was, measured 12 times on each test, three times under each of the four experimental conditions. The restriction placed upon the order of the con- ditions was that the first time a subject took the tests he was under the rest condition so that giving the instructions did not interfere with the condition nor the reverse.
Results and Discussion
The results are presented and analyzed separately for each of the dependent vari- ables studied. In each case reference is made to the paradigm presented in Table 1, and the code letters used refer to the designated experimental conditions and their combina- tions as a system for presenting the obtained means.
The experiment was conceived and designed to allow analysis of the results in two separate manners. The fact that each block of meas- ures taken on the twenty-four 5s is replicated twice allows the use of a within-individual estimate of variance to be used as an error
Experimental Design Indicating the Conditions of Measurement, and Their Relationships
n = 24
n = 24
j = 3
n = 24
j = 3
n = 24
j – 3
Effects of Fatigue and Anxiety 121
term to evaluate the effects of the treatment conditions on the variables in the population used. This error term contains variance of two types, that associated with instrument error and individual diurnal variation. This analysis is intended to test the theoretical and perhaps somewhat obvious question of whether these variables are affected by the treatment conditions of fatigue and anxiety in the sample used.
The second analysis, which uses an esti- mate of the individual differences variance as the error term, is intended to answer the question of whether these test variables are useful as reliable indices of the independ- ent variables for practical application. Fre- quently the question of whether a variable changes significantly as a result of such con- ditions as fatigue and anxiety has been con- fused with the question of whether it may be used as an adequate indicator of these con- ditions. The two analyses employed test each of these questions in turn with what is felt to be the proper error term for each. The second analysis also provided a test of the replications as a main effect, thus ena- bling a check on possible changes due to learn- ing, the presence of which of course would cast some question on their usefulness as indicators. In all cases tests of homogeneity of variance were satisfied. Table 2 presents the means for each experimental condition for each of the dependent variables used, ac- cording to the paradigm in Table 1. Tables 3 and 4 present composite results of the tests of significance. Reference is made to these three tables in the description of results for each type of experimental measure.
Steadiness. The total mean score for all sub- jects under all conditions was 72.23; for con- dition F-O = 62.0, F = 82.46, A-0 = 72.25, A = 72.22. The differences associated with fatigue conditions are significant at the .001 level, as are individual differences. Anxiety conditions effected no change in the measures.
There is a questionable interaction between fatigue and anxiety, and the interaction be- tween fatigue and individual differences is very significant as is the interaction of anxiety and individual differences. From these com- binations of interactions it appears that anx-
Means of Experimental Results for Specified Tests and Conditions
Body Sway Anx.
Body Sway . Time Anx-
62 00 82.46
540 62 652 97
iety may act here to increase the scores of some individuals and decrease or not affect the scores of others, thus destroying the main effect. Anxiety then may be acting as a sensitizer to fatigue effects in some instances and a desensitizer in other instances. No significant change was observed in successive
122 S. Ross, T. A. Hussman, and T. G. Andrews
Analyses of Variance for the Specified Experimental Variables, Using “Within Individuals” as Measure of Experimental Error’
Fatigue Conditions Anxiety Conditions Individuals Interactions :
Fat. X Anx. Fat. X Ind. Anx. X Ind. Fat. X Anx. X Ind.
Error . Within Individuals
1 23 23 23
MS for Steadiness
718.83* 322.07*** 301.88** 191.63
MS for Body Sway
2,628.12*** 333.68** 341.42***
3.S6 64.24* 68.32** 77.48**
MS for Body Sway-Time
299,215.59* 84,111.68 54,416.36
MS for Tapping
957.03*** 148.78* 730.70***
552.78*** 29.16 94.64*** 59.87
MS for CFF
51.77*** 5.48*** 4.68** 3.30
1 The asterisks identify the conventional levels of significance: * for .05, ** for .01, and *** for .001.
measurements on the same individual under the same condition. The general conclusion here is that fatigue produces a general de- crease in steadiness.
Body Sway. The total mean score for all conditions was 30.26; for condition F-0 = 27.24, F = 33.3, A-0 = 29.18, A = 31.35. Fatigue effects very significantly increase
body sway, and anxiety appears also signifi- cantly to produce the same results. Indi- vidual differences are also significant here. The interactions were insignificant when com- pared with the highest order interaction, as recommended by McNemar (10). No sig- nificant effects were obtained for repeated measures under the same conditions. The
Analyses of Variance for the Specified Experimental Variables, Using “Within Cells” as Measure of Experimental Error’
Fatigue Conditions Anxiety Conditions Replications Interactions :
Fat. X Anx. Fat. X Repl. Anx. X Repl. Fat. X Anx. X Repl.
Error : Within Cells
1 1 2
1 2 2 2
MS for Steadiness
MS for Body Sway
3.56 3204 60.59 5.59
MS for Body Sway-Time
299,215.59*** 45,262.12** 20,433.86
MS for Tapping
957.03** 148.78 354.59*
552.78* 3.94 8.53
MS for CFF
51.77 7.84 2.41 5.52
1 The asterisks identify the conventional levels of significance: * for .05, ** for .01, and *** for .001.
Effects of Fatigue and Anxiety 123
general conclusion here is that fatigue and anxiety both increase body sway and signifi- cantly more for some individuals than for others. The results obtained serve to cor- roborate other studies on steadiness and body sway (1,4,5,6,7, 11, 18).
Body Sway Time Scores. The total mean score for all conditions was 596.80; for con- dition F-0 = 540.62, F = 652.97, A-0 = 614.30, A = 579.30. Fatigue effects are very reliable in their action to increase these scores. However, replication measures under the same conditions as well as differences among individuals were also highly significant. Be- cause of these features and a very significant triple interaction effect, there was judged to be such a large amount of uncontrolled vari- ability that no definite conclusions are offered for this measure of behavior decrement.
Tapping. The total mean score for all conditions was 81.47; for condition F-0 = 79.64, F = 83.29, A-0 = 80.75, A = 82.18. As in the case of the body sway time scores, there is a large amount of uncontrolled vari- ability evidenced for the tapping measures. The fatigue condition acted to increase tap- ping reliably. However, replications within the same conditions as well as individual dif- ferences proved significant. There is prob- ably too great a learning factor allowed in the conditions of measurement of tapping. The results in general indicate that the tap- ping test would be a sensitive indicator of behavior decrement if the learning factor were better controlled.
Critical Flicker Frequency. The total mean score for all conditions was 48.598: for condition F-0 = 48.555, F = 48.641, A-O = 49.005, A = 48.190. Fatigue alone did not produce any significant change, but anxiety effects were highly significant in their de- crease of CFF. Individual differences were significant, and replication effects were not significant.
Examination of the significance of the in- teractions in the case of CFF suggests that the same relationship holds between fatigue and CFF that obtained between anxiety and steadiness. The interaction between anxiety and individuals is significant, indicating a differential effect. The interaction of fatigue
and individuals is also present and suggests that some individuals change in one direction here while others change minimally or in the other direction, thus reducing the main effect that is predictable from fatigue. A more im- portant interaction is found between the main effects of fatigue and anxiety. From the spe- cific results obtained with CFF, it appears that this test may be a useful one for studies on behavior decrement only in situations of individual cases.
Interrelationships Among the Measures. In- tercorrelations were obtained among the av- erage scores of the tests as they appeared under the rest or control condition. These Pearson correlations were obtained only on the 24 5s, and it was found that only two such correlations were significant. These were the correlations between steadiness and body sway (r = .550) and between steadiness and the body sway time scores (r = .407).
Body sway appears to have a factor in com- mon with steadiness, and this is possibly the reason that body sway measures were found to be adequate indices of the stress involved in this investigation. It is also possible that the body sway test involves a factor or fac- tors not present in the steadiness test, because the former was found to be a significant indi- cator of anxiety effects, while this did not hold for the steadiness test.
There was one source of variation that was impossible to control, namely the actual amount of bodily damage or physical punish- ment sustained by each of the 5s during the conditions of competitive boxing. It was felt that some system should be instituted that would allow a possible check on the validity of some of the experimental assumptions, and so correlations were computed between the number of head blows received and scores on each of the tests. The estimates of head blows were furnished by Mr. Frank Cronin, the University Boxing Coach, who observed every bout and tallied blows on a prear- ranged data form. None of the correlations was found to be statistically significant on a one-tail t test, which is the appropriate test considering the hypothesis in this case. It would appear that within the limits of the measuring techniques and the design of the
124 S. Ross, T. A. Hussman, and T. G. Andrews
study, the number of head blows sustained had little or no effect on the test scores of the 5s.
As part of another investigation, to be re- ported elsewhere, protracted boxing experi- ence with its attendant number of head blows produced no reliably indicated changes in the electroencephalographic records of ama- teur boxers, some of whom were from among the 5s used in the present investigation.
As far as the present results are concerned, it appears that measures of steadiness more than the other variables tested satisfy more of the criteria of reliability and predictability to be used as indicators of behavior decre- ment. Hand steadiness serves for indications of fatigue, and body sway which is a form of steadiness measure serves for indication of either fatigue or the type of anxiety produced in this study. These suggestive results may be taken as recommendations for further in- vestigations under a greater variety of stress conditions.
The other variables employed in this study may be made into more useful measures for studies of stress if their trial-to-trial varia- tion and very wide individual differences may be diminished by deriving scores through other techniques, reducing practice effects, and otherwise accounting for the larger rela- tive amounts of variability now classifiable as experimental error.
Summary and Conclusions
As part of a larger research program on indicators of behavior decrement, this experi- ment investigated the comparative value of several selected measures of behavior decre- ment under conditions of fatigue and anxiety. The dependent variables chosen as possible indicators of behavior decrement were: (a) steadiness; (b) body sway; (c) body sway time score; (d) tapping rate; and (e) criti- cal flicker frequency. The primary purpose of the experiment was to determine whether or not performance on each of the five de- pendent variables changed significantly as a result of intensive muscular exercise (fatigue) or the fear of bodily injury (anxiety) or the interaction of these conditions in the collegi- ate competitive boxing situation.
Twenty-four boxers were measured under the following four conditions: at rest; after heavy exercise; before fighting; and after fighting. The tests were administered three times to each subject under each of the ex- perimental conditions. The analysis of vari- ance technique was used to test the changes in each variable as a function of the inde- pendent variables. Two separate analyses of the results were made: (1) using “within in- dividuals”; and (2) using “within cells” as the measure of experimental error. The re- sults permit the following major conclusions:
1. Hand steadiness scores decreased sig- nificantly with fatigue, but not with the anx- iety conditions. No significant change was observed in successive testing on the same individual under the same conditions.
2. Fatigue and anxiety significantly in- creased body sway scores.
3. Body sway time scores were found to be unreliable, although the fatigue conditions significantly increased these scores.
4. Tapping was found to be unreliable, possibly due to a learning factor. Significant changes were found, however, in the test scores as a result of both fatigue and anxiety.
5. Critical flicker frequency thresholds were shown to decrease significantly as a re- sult of anxiety. The reliability of the test was high, and it is felt that it may be useful in studies of behavior decrement in situations of individual cases.
6. No relationship was found between the dependent variables used and the number of head blows received by the subjects during a boxing bout.
7. Measures of steadiness more than the other variables tested satisfy the criteria for indicators of behavior decrement. Hand steadiness serves as an indicator of fatigue, and body sway (which is a form of steadi- ness measure) may serve as an indicator of either fatigue or the type of anxiety produced in the experiment. The remaining variables tested in this experiment may be made into more useful measures for studies of the effects of stress if trial-to-trial variation and the very wide individual differences exhibited are di- minished.
Received June 8, 1953.
Effects of Fatigue and Anxiety 125
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