Indian J Physiol Pharmacol 1997; 41 (4) : 409-415

MUSCLE POWER, DEXTERITY SKILL AND VISUAL PERCEPTIONIN COMMUNITY HOME GIRLS TRAINED IN YOGAOR SPORTS AND IN REGULAR SCHOOL GIRLS

P. RAGHURAJ AND SHIRLEY TELLES*

Vivekananda Kendra Yoga Research Foundation,19, Eknath Bhavan, K. G. Nagar,Bangalore - 560 019

( Received on March 15, 1997)

Abstract: The present study was conducted to compare critical flickerfusion frequency (CFF), degree of optical illusion C'di"), dexterity scores,and grip strength in three groups of subjects, viz community home girlswho had learned yoga for 6 months (CHY), age-matched community homegirls who had physical activity training for 6 months (CHP), and girls whowere attending a regular school (SCH). There were equal numbers in eachgroup for each of the 4 assessment (range 11 to 30 subjects) and age rangewas 12 to 16 years of age. The CHP group had significantly lower CFF and"di" was significantly higher (one factor ANOVA, t test for unpaired data)in the CHP group, both compared to CHY and SCH groups. Right handgrip strength was also significantly less in the CHP group compared toSCH. The results were explained by previous reports of high levels ofanxiety and aggression in community-home groups, which is known toinfluence the four parameters described here. The better performance ofthe CHY group compared to CHP, suggested that yoga practice has abeneficial effect in these subjects.

Key words: community homephysical activity

INTRODUCTION

Children who are unable to adjust athome, at school or in society are admittedto community homes. Previous studies haveestablished that these children were sociallyand emotionally traumatized, althoughphysically normal (1). They also reportedanxiety and fears and were more aggressive.A report on physiological measures showedthat the resting electrical activity in

yogamotor strength and skill

visual per::eption

selected facial and back muscles (EMG) wassignificantly higher in community homeboys compared to boys of the same age inan ordinary school (2). This increase wasattributed to a high level of stress, as theEMG tone was found to decrease after thesubj ects underwent a program whichincluded both physical training andrelaxation. A subsequent report comparedthe effects of increased physical activitywith those of relaxation with awareness

*Corresponding Author

410 Raghuraj and Telles

through yoga in community home girls (3).To begin with, community home girls hadhigher respiratory rates and lower skinresistance values compared to an agematched group of girls who were staying athome and attending a regular school. At theend of six months the community-home yogagroup had a greater decrease in heart rate,respiratory rate and an increase in skinresistance, compared to a matched,community-home physical activity group.These changes also suggested that yogadecreased physiological signs of stress.

The present study was conducted tocompare the motor and sensory (visual)performance of community home girls whohad learnt yoga with that of community-home girls trained in physical activity andof girls staying at home. Four tests wereused, viz. (0 hand grip strength as anindicator of muscle power, (ii) degree ofoptical illusion using Muller-Lyer lines asa measure of accuracy of visual perception,(iii) critical flicker fusion frequency also toassess visual perception, and (iv) tweezerdexterity to assess motor skills. Thecommunity-home girls belonged to twocategories. Prior to the assessments onecategory had training in yoga for sixmonths, while the other category had aprogram of increased physical activity forthe same duration. This study also comparedboth categories of community-home girlswith age matched girls from an ordinaryschool.

METHODS

Subjects: The subjects were 80 girls froma state community-home. They werebetween 12 and 16 years of age and had

Indian J Physiol Pharmacol 1997; 41 (4)

been admitted because of difficulty inadjusting at home, at school, or in society.Fifteen were from broken homes, with oneor both parents dead or separated. Theirduration of stay in the home ranged from 6to 36 months. The 80 girls were divided intopairs matched for age and duration of stayin the home. It was possible to form 30 suchpairs. Subjects of a pair were randomlyassigned to either one of two groups, viz.yoga (CHY) and physical activity (CHP). Athird group of girls who were staying athome and attending an ordinary school(SCH), were matched as far as possible forage (± 6 months to 2 years) with the twogroups from the community-home. All threegroups (CHP, CHY, SCH) were assessedsimilarly. However, it was not possible tocollect data on the degree of optical illusionin the control (SCH) subjects. Hence dataobtained on adults living at home were usedas control values. For each of the tests thenumber of subjects was different (Table I).

Design of the study: All three groups,i.e. community-home group who hadpractised yoga for six months (CHY),community-home group who had training inphysical activity for the same duration(CHP), and girls who were staying at homeand attending a normal school (SCH), (oras described above, for the degree of illusionassessment, normal adults), were assessedfor" each of the four tests (detailed below)on four separate occasions.

Parameters: All subjects were assessedin the four parameters described below:

(i) Hand grip strength was measuredusing a hand grip dynamometer. Subjectswere asked to extend their arms horizontally

Indian J Physiol Pharmacol 1997; 41 (4) Sensorimotor Skills in Community Home Girls 411

TABLE I: Number of subjects (n) and mean age ± SD of each group for all the four assessments.

Groups

Assessment n CHY CHP SCH

Mean age SD Mean age SD Mean age SDGripstrength 1.3 1.411 13.9

Tweezerdexterity 15 13.6 2.9

Criticalflickerfusion 30 13.9 1.9

Opticalillusion 30 13.9 1.9 12.9 2.6 28.9* 6.3

* = adult subjects

parallel to the ground, without support andgrip the dynamometer using maximumstrength. Three trials were given for eachhand, alternately, with 10 see gap betweentrials. The highest among the three valueswas used for analysis.

(ii) Tweezer dexterity was measuredusing the O'Connor tweezer dexterityapparatus, which consists of a metal platewhich has 100 holes (2.0 mm in diameterand 20.0 mm deep) spaced 15.0 mm apart.The subject was instructed to pick up metalpins (1.5 mm in diameter and 25.0 mm inlength) with a tweezer and place them inthe holes as quickly as possible. The numberof pins placed within 4 min was noted.

(iii) Critical flicker fusion frequency wasmeasured using an electronic flicker fusionapparatus, with flicker rate ranging from12 to 95 Hz. The flickering stimulus was ared light, 6 mm in diameter with intensityof 50 mcd, surrounded by a white surfacewith illumination of 150 lux. Subjects wereseated 50 em away from the apparatus, withtheir gaze on level with it. All subjects were

13.6 13.8 1.1

13.8 1.8 1.811.4

12.9 13.6 1.52.6

assessed in ten ascending trials, whichbegan with minimum frequency (12 Hz forthe apparatus used). The frequency wasincreased at the rate of 0.5 Hz per step, tillthe subjects felt that the stimulus was nolonger flickering, i.e. it was "fused" (fusionthreshold).

(iv) Opticalillusion. was measured usingMuller-Lyer lines. Subjects were assessedin two types of trials, i.e. "in" and "out"using "the method of limits", with theexperimenter varying the lengths of thelines. The Muller-Lyer lines, though of equallength, appear unequal due to two differenttypes of arrows drawn at the ends of theline. In the apparatus used for the presentstudy, the line on the left had close-endedarrows at either end, making it appearshorter. The length was fixed (in mrn). Incontrast the length of the line on the rightcould be varied. This line had open-endedarrows at either end which made it appearlonger. The experimenter manipulated thelength of the line according to the subject'sspecifications. The exact position at whichthe subject perceived the two lines to be of

412 Raghuraj and Telles

equal length was noted, i.e. subjectivereading - "sr". The difference between thereading at which the lines were actuallyequal and the "sr" gave the degree ofillusion, "di". Each subject of three groupswas assessed in two types of trials (ten each,give alternately). For "in" trials theexaminer adjusted the length of theadjustable line, 1 mm at a time, changingthe length from maximum (200 mrn) till thesubjects perceived the length to be equal tothat of the fixed line (actual length = 160mm). For "out" trial the procedure wasreverse, the adjustable line was kept tominimum length and the length wasgradually increased till the subjectsperceived the length to equal that of thefixed line. In both cases the difference (inmrn) between the actual length of the fixedline and the perceived length was noted asthe degree of illusion, "di".

For all 4 tests the apparatuses were fromAnand Agencies, Pune, India

Yoga training: Staff members of thecommunity-home who were previouslytrained in yoga, were involved in teachingand supervision. A trained yoga teachervisited the class every fortnight to checkthe practice. Yoga techniques included: (i)simple yogasanas for 50 minutes, (these arepostures which are maintained for as longas possible, while relaxed), and (ii) a 10minute period of relaxation in shavasan(corpse posture). Throughout both practicesthe emphasis was on relaxation andawareness of physical and other sensations.

Physical act un.ty : Physical activitytraining included stationary jogging, rapidbending forwards and backwards, twisting,

Indian J Physiol Pharmacol 1997; 41 (4)

and bending sidewards. These pr act iceswere for 40 minutes. The session alsoincluded 20 minutes of playing games suchas relay races in which all the girls had toparticipate actively.

RESULTS

The data for all four assessments (gripstrength, tweezer dexterity, critical flickerfusion frequency, and degree of opticalillusion (Mul Ier-Lyer lin es l) of the three

CRITICAL FLICKER FUSION FREQUENCY

Hz

~CHY ~CHP DSCH

DEGREE OF OPTICAL ILLUSION

OUTTRIALS5 ••t:

em 3IN TRIALS

2

1

OL..---.J<:.=~-L_~

~CHY WCHP DSCH

•• p< -OS .11- P< -001

Fig. 1: Critical flicker fusion frequency and degree ofoptical illusion in community home yoga group(CHY) and community home physical training group(CHP) compared to ordinary school group (SCH).*P<.05, **P<.OOl, 't' test for unpaired data.

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groups were compared for significantdifferences using separate single-factoranalysis of variance (ANOVA). The groupaverage values were tested for significantdifferences using the 't' test for unpaireddata comparing two groups at a time. Thesingle factor ANOVA showed a significantdifference between the critical flicker fusionfrequency values of the 3 groups, [F = 18.36,F.001 (2) 2, 87 = 8.30, hence P<.OOl] andfor the degree of optical illusion using theMuller-Lyer lines during "in trials" [F =18.99, F.001 (2) 2, 87 = 8.30, hence P<.OOl]

HAND GRIP STRENGTH

RIGHT HAND LEFT HAND

~CHY ill]CHP DSCH

TWEEZER DEXTERITY

50

No. of pins/1.0I. min 30

20

~CHY C3 CHP DSCH

Fig. 2: Hand grip strength and tweezer dexterity scoresin community home yoga group (CHY) andcommunity home physical training group (CHP)compared to ordinary school group (SCH).

Sensorimotor Skills in Community Home Girls 413

(Fig. 1). There was no significant differencebetween the three groups for degree ofoptical illusion for "out trials", hand gripstrength scores obtained for either hand orfor the tweezer dexterity scores (P<O.l inboth cases) (Fig. 2).

The 't' test for unpaired data showed thefollowing significant differences (i) Criticalflicker fusion frequency was significantlylower in the CHP group, compared to SCHgroup (t = 5.72, P<.OOl) and compared toCHY group (t = 5.72, P<O.Ol). (ii) Degree ofoptical illusion for "out trials" i.e. the "di"was significantly higher (marginaldifference) in the CHP group compared toSCH ( t = 1.92, P<.05). (iii) Grip strengthwas significantly lower in CHP groupcompared to SCH group for the right hand(t = 2.00, P<.05, one tailed).

DISCUSSION

The present study showed thatcommunity home girls who had receivedphysical training (CHP group) havesignificantly lower critical flicker fusionfrequency (CFF), higher degree of opticalillusion ("di") for "out trials", but not for"in trials", and lower right hand gripstrength compared to girls of the same agewho were staying at home and attendingan ordinary school (SCH group). Thecommunity home girls who had received sixmonths of training in yoga (CHY group)performed better i.e. higher CFF, lower "di"on "out trials" and marginally greater handgrip strength, than the CHP group, andwere not significantly different from theSCH group. The data of the community-home groups before they had learned yoga/physical training were not available. Hence

414 Raghuraj and Telles

the baseline performance of these groups ofsubjects was not known.

The CFF has been correlated withfactors such as physical stresses e.g.nutritional deficiency, fatigue duringphysical work, or sleep deprivation (4) aswell as emotional stress (5). Greater stresslevels have been correlated with lower CFFvalues. The "di" has also been correlatedwith cognitive factors such as theexperience, hypotheses, and strategies ofjudgement (6). In the present study, thelower CFF values and higher "di" in the"physical activity" community home groupcould possibly be related to the higher stresslevels, which earlier reports indicated thatthese subjects were specially likely to have(1, 2, 3). The CHY group did not havesignificantly different values for both CFFand "di" compared to SCH group. This couldbe related to the fact that the practice ofyoga for short periods (10 to 30 days) hasbeen shown to increase the CFF (7) andreduce optical illusion (8).

The hand grip strength and tweezerdexterity scores did not differ significantlybetween the three groups using a singlefactor ANOVA. However, the 't' test forunpaired data showed a significantly lowerright hand grip strength in the CHP groupcompared to SCH group. The absence ofmajor differences between the groups forthese two parameters could be explained ineither of two ways, viz (i) the factorsresponsible for lower visual sensitivity (lowCFF, high "di") in the CHP group ofcommunity home girls may not be applicableto grip strength/tweezer dexterity; (i i)alternatively, both yoga and increasedphysical activity may have been effective in

Indian J Physiol Pharmacol 1997; 41 (4)

reducing adverse factors in the CHP andCHY groups with regard to grip strength ordexterity scores while there were stilldifferences in CFF and "di". The gripstrength and dexterity scores of the threegroups hence appeared the same. Theformer explanation is contradicted by a veryearly report in the literature whichdescribes poor performance in "asylum"children when hand grip strength andmanual dexterity were tested (9). The latterexplanation may be more acceptable. Thereare reports that the practice of yogaincreases grip strength (10) and improvesdexterity. A previous study has shown acomparable effect of yoga and physicaltraining on grip strength and specific tasksrequiring motor skills (11). This also mayexplain why no differences were observedbetween the two groups of community homegirls for these two parameters, even thoughthe CHP group had lower right hand gripstrength than the SCH group. Thephysiological basis for the perception ofoptical illusion and of a flickering lightstimulus are similar. In both cases changesat retinal, cortical and cognitive-judgemental levels influence visualperception. However, in the case of flickerfusion, the peripheral visual pathway isspecially important, and may be related tothe frequency at which the optic tractdischarges and to the discharge rate of "on-off" ganglion cells in response to anintermittent stimulus. Also in the perceptionof an optical illusion cognitive-judgementalfactor are stressed (6).

The hand grip is believed to beinfluenced by the availability of energy andoxidation requirement (12). These factorsmay also be expected to influence the

Indian J Physiol Pharmacol 1997; 41 (4)

performance in a repetitive task requirmgfine motor skills (i.e. the dexterity test).

Hence the present study suggests thatthe reported higher stress levels incommunity home inmates reduced sensoryperception by causing change at peripheraland central levels. To some extent yogapractice modifies this effect. Similarly muscle

Sensorimotor Skills in Community Home Girls 415

power (but not fine motor skill) was less inthe community home group. Yoga practice alsoappeared to improve hand grip strength,perhaps by reducing the energy requirement.However, additional information on thebaseline status of the community home group,prior to either training (which was notavailable in the present study), would berequired to draw more definitive conclus ions.

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