In this experiment the comparison was studied between the muscular and the nervous fatigue and the flicker phenomenal value of the optic nerve. In order to measure the physical fatigue, various methods have been reported by many authers. In this experiment, a quantification of the fatigue was tried though the relation between the amount of mental activity and the FF (flicker frequency), which is useful in physical fatigue measurement with the change in respiration and pulse. In measuring the FF, respiration and pulse caused by physical work, it shows that the these three measured values are somewhat exponential, which might be called the exponential accumlation of fatigue. In mental activity slight relation was also found between fatigue and learning

Harano, Hiromi

Kikuchi, Susumu

Miyazaki, Yoshiyuki

English

Okayama University Scientific Achievement Repository

MEMOIRS OF THE SCHOOL OF ENGINEERING, OKAYAMA UNIVERSITY, Vol. I, No. I, MARCH, 1966On Physical and Mental Fatigue*Susumu KIKUCHI, Hiromi HARANODepartment of Industrial Scienceand Yoshiyuki MIYAZAKIDepartment of Mechanical Engineering(Received November 20, 1965)In this experiment the comparison was studied between the muscular andthe nervous fatigue and the flicker phenomenal value of the optic nerve.In order to measure the physical fatigue, various methods have been reportedby many authers. In this experiment, a quantification of the fatigue was triedthough the relation between the amount of mental activity and the FF (flickerfrequency), which is useful in physical fatigue measurement with the changein respiration and pulse. In measuring the FF, respiration and pulse caused byphysical work, it shows that the these three measured values are somewhatexponential, which might be called the exponential accumlation of fatigue. Inmental activity slight relation was also found between fatigue and learning.§ 1. IntroductionIn recent industry, there have been appearingvarious fatigue with the increasement of work.Threfore, some considerations on such a com-plicated fatigue will not be useless.The fatigue is caused and appeared in variousways, e.g., by purely mental activity, by purelyphysical work, and by various mixture of these.In this experiment we used the self-made bi-cycle ergometer to measure the physical fatigue.The FF, the amount of CO2 in expiratory air,and the pulse were measured three times, name-ly, just before working, during working andjust after working. The change in these mea-sures shows the amount of physical load by thesimple physical work of revolving the bicycle.In this case, the work was regarded as a purelyphysical work, that is, the work was free frommental activity.In order to examine the mental fatigue, weused the tracking work by an analog computerwas adopted. The fatigue was measured indi-rectly by observing the change of the amountof work and the FF. Tracking work was con-sisted of visual activity and response actionthrough mental feed back.§ 2. Experimental Procedure1. SubjectsIn the experiment of the physical fatigue,6 males and 1 female of from 19 to 25 yearswere subjected. Everyone of these 7 persons* Aided by the Grant from the Ministry of Educationfor 1965.had a good physical constitution and was ingood health.For the mental fatigue experiment, a 21 yearsold male was chosen in a random way. Thismale also had a good physical constitution andwas in good health, but he always wore glasses.2. MethodsThe physical load was given by revolving theself-made bicycle ergometer. Each person re-volved this bicycle for 30 minutes at a time withthe average speed of 15 revolution per minuteand with the average load of 5-7 kg on thebrawny brake.The measurement of the following three itemswere carried out just before the activity and atevery third minutes during the work.(1) Flicker test-A FF counting machine wasused.(2) Amount of respiration-The expiratory airwas taken from each person into a test tubeand the amount of CO2 contained in it wasquantified by analyzing it by means of agas analyzer.(3) Pulse-The number of pulse was countedon the radial artery during the period of30 seconds.For the mental fatigue experiment, an analogcomputer and Braun tube oscilloscope were usedas shown in Fig. 1, and complex input signal wasgiven and the pursuit operation was made toreduce the deflection from the cardinal line ofthe oscilloscope to the least in the tracking acti-vity to the input signal. The flicker test wasmade every 30 minutes during the work. As in106On Physical and Mental Fatigue 107"-PotentiometerSillulpulTable 1Average variation of physical work(7 Subjects)eed Bock i9f'101Fig. 1 Schem'ltic diagram of experiment.shown in Fig. 2, where there are the inputsignal, the maniplated variable, and the amountof error in the foregoing two. The results wereevaluated through the error area between theinput and the amount of work.§ 3. ResultsFig. 3 & 4 and Tab. 1 show the average varia-tion before and after the loading of physicalwork among the 7 persons tested.FF Pulse i CO2Time decreasing increasingI(min)ratio (%) ratio (%) (%)Before I -- 1.183 5.1 2.5 2.906 6.4 3.4 3.169 7.4 3.7 3.1712 7.3 4.0 3.4115 9.0 4.3 3.8818 8.3 4.9 3.6021 8.7 5.1 3.432! 7.6 5.7 4.2627 9.6 5.8 4.28_._-The FF in this case was intendency of de-crease, that is, its average was 30.7 <cis) beforethe loading and reduced by 8.8% after 30 minu-tes' work.The number of pulse also decreased, but theresults showed less dispersion than the othertwo.Fig. 5 and Tab. 2 show the variation in the FFbefore and after the mental activity. Fig. 6JIO150100Time (min)Fig. 5 FF diagram of mental fatigue.'0"co,......L4''---!----,~-7-'ci-2 -+";--1~--2~--tr- 30Tim, (minIFig.3 FF, CCh pulse diagram of physicalfatigue.10•8:l50I I'6 7 6 910Fig. 4 Logarithmic presentation of physicalfatigue.Time (miniFig. 6 Logarithmic presentation of mentalfatigue.108 S. KIKUCHI, H. HARANO and Y. MIYAZAKI (Vol. 1,"L..,1,0,---1.-L-'--&-.l-l-----L-L~-------LJ--~-L-L~-Time (min)Fig. 7 Presentation of transformation of maniplatedarea with time.Table 2Variation of mental activityy=0.18 t1.0 18 •y=1.3 to.15°3t; timeThese eq,uations show that the decreasingratio during the first 10 minutes after the loadingis great and then becomes gradually saturated.The number cf pulse counted during the sameperiod as the FF showed the similar decreasetendency. However, after 30 minutes' work thepulse number increased by 696. The variationbetween before the loading (73/min) and at thefourth minutes a after the loading (91/min) wasthe greatest, then gradually increase, and showedno remarkable increase. The results could beexpressed approximatly in a curve, which showsthat there were no individual difference in eachpulse counts because the tested persons were ofabout same age and young people.But, the variation in the amount of CO2 in theexpiratory air showed a different tendency fromabove two. The amount of CO2 gradually in-creased with the continuation of work, but itsincrease ratio was inconsistent and irregular.Fig. 5 shows the FF variation of mental acti-vity. The decreasing ratio of the FF was about5% after 60 minutes' working and 12% after 1,0minutes' loading of work. This is represented bythe both logarithmic graph in Fig. 6, and may beregarded as exponential. The following equationwill express the curve,Compare::! with the physical FF, this curveshows a less increasing at an early stage, butwith course of time, the exponential gradientshows that the mental FF becomes increasingmore than in physical work.Fig. 7 is the plotted results of the error areain the tracking acts. The fatigue shows that oneis apt to learn the given work during the first60 minutes, then go into a weary conditionduring the second 30 minutes, decrease one'sworking speed during the next 30 minutes, andthen during the fourth 30 minutes gradually in-crease it, attaining to its peak after 160 minutes'working, and again decrease one's workingspeed gradually.Both mental and physical works are done veryeffectively at first and then in a weary conditionor in the fatigue with a repeated periodicityabout fO minutes, and during these repeatedrhythms the fatigue will be accumulated.In this experiment different measuring me-......--~~Time Flo' Error erea(min) decreasing (cm2/min)ratio (%)I---- ---_._~-1 6.510 14.020 6.830 12.440 -0.1 6.550 5.960 5.970 4.6 5.480 4.6 6.090 6.8 5.8100 5.4110 4.8120 11.0 5.3130 5.5140 6.0150 8.7 6.2160 12.2 5.4170shows a remarkable decrease of the FF logarith-mically. There is some relation between the FFand the manipulated variable is expressed bydimension in Fig. 7.§ 4. DiscussionThe statistical results of physical work (Fig.3), it was found that the decreasing ratio of theFF are functionally nondecreasing with the load,as an example the decreasing ratio of the FFwas 10% after 30 minutes' work. As might beknown from the both logarithmic graph in Fig.4, this ratio may be expressed by the exponen-tial function y = axb •Then, the curve obtained by way of try-and-error method may be expressed as,1966) On Physical and Mental Fatigue 109ReferencesR. Margaria & others: Ergonomics 8, (1965) 49.M. Ohshima: The Investigation of Fatigue (inJapanese), (1964).3) K. Hashimoto: J. of Ind. Med. Sci. (Japanese), 5(1963) no. 9, 563,4) M. Ogata & others: Okayama Igakkai Zassi 74,(1962) 269.M. Ogata: ]. of Ind. Med. Sci. (Japanese) 4, (1962)no, 4, 252.thods were used in order to know the fatigue indifferent forms of work and activity. It was 1)granted that the flicker test is effective for eva- 2)luating both physical and mental fatigue, andthe FF was practically measured in both cases.However, each fatigue will be after all different,even though several persons were tested.We wish to thank Professor Masana Ogata of 5)Okayama University, for his helpful advice.

On Physical and Mental Fatigue

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