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