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Cross Transfer Effects of Conditioning and Deconditioning on Muscular Strength LARRY G. SHAVER

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Physical Education Department , State University College at Brockport , Brockport, New York, 14420 Published online: 27 Apr 2007.

To cite this article: LARRY G. SHAVER (1975) Cross Transfer Effects of Conditioning and Deconditioning on Muscular Strength, Ergonomics, 18:1, 9-16, DOI: 10.1080/00140137508931435 To link to this article: http://dx.doi.org/10.1080/00140137508931435

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ERaONOMICS, 1975, VOL. 18, NO. 1, 9-16

Cross Transfer Effects of Conditioning and Deconditioning on Muscular Strength

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Physical Education Department. State University College a t Brockport. Brockport New York 14420 The purpose of the investigation was to study the effects of inactivity periods of 1, 4, 6, and 8 weeks on the retention of recently acquired levels of muscular strength in the ipsilateral and contralateral arms. The aubjccts (80 experimental and 20 control) were right.handed male volunteers. 18 to 22 yr. The experimental subjects participated threc times weekly in a 6-week high-intensity, low-repetition strength conditioning programme. Following training, the trained subjects were randomly divided into four experimental groups and stopped training for 1. 4, 6, or 8 weeks. Upon completion of the inactivity periods, a retention test was administered to both arms. The data analysis revealed that all experimental groups enhanced their isometric strength levels significantly in both arms during conditioning, thus demonstrating the phenomenon of cross-transfer of isometric strength. No significant differences were found for the control group. I t was also found that all experimental groups retained a significant amount of isometric strength acquisition in both arms following tho inactivity periods. No significant amount of strength was lost in the con4itioned as well as the nnconditioned arm despite 1 week of detraining. However, det,raining of 4, 6, and 8 wceks resulted in a significant loss in both 8mS. Finally, no significant differences a c r c found between the 6- and 8-week inactivity groups in the conditioned as well as the unconditioned arm.

I . Introduction The fact that the systematic exercise of the nluscles of one limb causes a definite increase of muscular strength in the contralateral extremity has been experimentally found in a number of studies since as early as 1894 when Scripture et al. 1894) introduced the term ' cross education '. Researchers (Davis 1942, Hellebrandt 1958, Walshe 1923, Wellock 1958) studying the theoretical basis of cross transfer have agreed that this phenomenon is the result of it diffusion of motor impulses to both the conditioned as well as the unconditioned sides. It appears that these impulses elicit isometric type contractions in the contralateral muscle groups. I n addition, Rasch and Morehouse (1957) have suggested that a large portion of increased strength in the contralateral arm may be related to appropriate training of the antigravity muscles to compensate for the effect of body balance during the exercise. Thus, once the necessary adjustments have been made by one side of the body as a result of unilateral training, patterns are established which are readily available to the other side of the body, thereby producing part of the contralateral effect. On the other hand, an alternative explanation may be that these changes resulted from raising the subject's tolerance to fatigue. For example, SlaterHammel (1950) has postulated that during strenuous and systematic exercise of one group of muscles, a person probably learns to ignore or tolerate the feelings of muscular fatigue for an increased period of time, thus allowing transfer to occur and thereby influence the performance of other muscle groups.

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Larry G. Shaver

Although considerable controversy still exists among investigators conccrning thc most effective means of developing cross transfer of strength, most rcsenrcliers agree that, in general, cross transfer of strength is greatest when work has been performed in overload (Hellebrandt 1958, Hellebrandt and Iloutz 1956, Hellcbrandt el al. 1947, Shaver 1970, Walters 1955). In spitc of the continued interest in the development of cross transfer of ~nusculurstrength in the contralateral limb, the literature is almost void of rcselmh dealing with the retention or maintenance of newly acquired levels of muscular strength in the contralateral limb once training has been curtatled. On thc other hand, scveral studies have been carried out involving strength retention in the exercised limb. Alullcr and Hettinger ( 1 954) found average clecrctnents in strength to be around 0.3 per cent per week follow~ngmaximal isometric training for several weeks. I n an earlier study not related to training, I (1958) calculi~tecl the loss in strength in the upper Muller I ~ C Hcttinger cxtrcrnity of 3 subjects after immobilization of one iwm in :I plaster cast for 3, 7, 9 :mi 14 days. Thcy found that the decrease of initial strength per day varied from 1 . 3 to 5.5 per cent of the initial strength Recently, Muller (1970) nicde a thorough review of training and of inactivity on muscle strength, and he suggcstcd that in the complete absence of any contraction of a, muscle by narcotising the nerve, strength decreases by about 5 per cent per day. In the onc available study concerning cross transfer of muscular strength rctcntion in the uncxcrci~edlimb, Shaver ( I 973) found no significant amount of newly acquired isometric strength gains were lost (0.7 per cent) in the contrali~teralarm despite I week of detraining On the other hand, he found that detraining of 3 and 5 weeks did result in a significant loss (average of I .:I per ccnt). I n view of the limited research completed in this important area of study, this mvcstigation was conducted to determine ( a ) the effects of a &week, high-intensity, low-repetition, isotonic conditioning program on muscular strength in the ipsilateral (conditioned) and contralatcral (unconditioned) ~brms,and ( b ) the effccts of inactivity periods of 1, 4, 6 and 8 weeks on the retention of recently acquired levels of muscular strength in the ipsilateral and contralateral arms.

2. Method 'I'hc subjects, 100 m d e right-handed volunteers, I 8 t o 22 yr, were from the S t i ~ t cUniversity College a t Brockport, New York. All subjects were tested for maximum isometric strength of the flexor muscles of each forearm before and after (iweeks of high-intensity, low-repetition strength training. Isometric strength was measured as the amount of tension t h a t could be registered on a ct~blctensiometer. Testing procedures were adapted from those developed by Clarke (1963) for use with this instrument. The test was administered with the subjcct in a supine position on a strength table with his tested arm flexed to 90' a t thc elbow. l'lirce trials were administered with kach arm and t h e ctvertLge taken ils muximum strength. Upoti completion of preconditioning tests, subjects mere randomly assigned to cxperimcnt:d ( N = 80) and control ' ( N = 20) groups The experimental gruup trained in right m n elbow flexion curls three times weekly for 6 weeks

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Conditioning and Deconditioning on llluscular Strength

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using progressive resistance weight-training techniques (Delorrnc and Watkins 1854). The twining programme each day consisted of: ( I ) 1 set of I0 repetitions, with 4 10 RM (2) 1 set of 10 repetitions, with f 10 RM (3) 1 set of 10 repetitions, with 10 RM A two min rest interval was used between each set of curls. During the training period, the control group participated only in such activities as instructional badminton and volleyball, whereas the experimental group took part in these activities as well as the training programme. ~ o l l o w i nthe ~ 6 weeks of conditioning, all subjects in the control and experimental groups were retested for isometric strength in both arms, and in a manner patterned after the initial examination period. Differences between the pre-test and post-test scores was the amount of isometric strength that had been developed during the training programme. At the end of the &week developmental period, the trained subjects were randomly assigned t o 4 experimental groups, and the groups, in turn, were randomly assigned to varying pcriods of inactivity. Croup I ceased training for I week, Gronp I1 remained inactive for 4 weeks, Group I I I stopped training for 6 weeks, and Group TV did not train for 8 weeks before returning for the retention test. Following completion of their respective inactivity periods, the experimental as well as the control subjects were retested (this represented the subject's retent,ion test score) for isometric strength in both arms following the pre- and post-conditioning testing procedures. Using Sysler and Stull's (1970) procedures, an isometric retention strength score was then found in both arms by subtracting the pretest score from the retention test score. This represented the amount of recently acquired isometric strength which remained following the inactivity period. When the retention test score was subtracted from the post-test score for both arms, the remainder rcpresented the amount of isometric strength lost as a, result of the respective inactivity period. 7'his difference was referred to as the 'decrement score' (Sysler and Stull 3970, Waldman and Stull 1969). 3. Results The results of the three tests for both the ipsilateral and contralateral arms are found in Table 1. Statistical comparisons were also made among as well as within b~oups. The 0.05 level was used for all tests of significance.

3.1. Among-Group Analysis An anahysis of variance (randomized complete block design) was employed to find out if there were any significant ison~etricstrength differences among the 5 groups. The findings indicated no significant differences ( E= 1.23) among groups for the ipsilateral arm before the conditioning period. In addition, no significant differences (F=1.01) were found for the contralateral arm prior to the training period. However, when the training programme was completed, significant differences were found for the ipsilateral arm ( F = 12.65) as well ;IS for the contrslateral arm (F=9.40). Studenl-h7etu?,lc~~~Keuls' Multiple 12anye Tesb (Winer 1962) was.employed to determine which differences among groups mere significant. Mean differences were found

Larry G. Shaver Tahlo 1. Summary of maximum isometric strength test results* Insilateral Test Pre

Contralateral

Group

I

Control

Control Retention

I

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1V Cont,rol

* All scores presented in Newtons. between the control and the 4 experimental groups, thus indicating t h a t all experimental groups itnproved their isometric strength in both arms during the 6-week conditioning programme. No significant mean differences were found between the 4 experimental groups. Tn order to determine whether the groups differed in the a n ~ o u nof t isometric strcngth lost in each arm over the respective inactivity periods, an analysis of variance was computed on the decrement scores. The resulting F ratios of 9.75 for the ipsilateral arm and 7.25 for the contralateral arm were significant. Student-Newman-Keuls' Nultiple R m g e Test demonstrated that the groups which ceased training for 4, 6 and 8 weeks lost more strength in both arms than did the control group as well as the group which remained inactive for I wcck. I n addition, no significant differences were found between the 0- and 8-wcck inactivity groups in the exercised as well as the unexercised arm. Finally, no significant differences were found between the control group and t h e I-wcek inactivity group in both arms. 3.2. IYithin-Group Analysis The pre-, post-, and retention data of each group was statistically analysed by analysis of variance using a completely randomized block design. The findings of 12.82 for Group I , 13.03 for Group 11, 15.76 for Group I I I , and 18.97 for Group I V were significant for isometric strength for the ipsilateral a . I n addition, P ratios of 9.67 for Group I, 11.62 for Group I I , 13.45 for Group 111, and 15.25 for Group IV were significant for the contralateral arm. No significant differences existed for the control group for the ipsilateral ( F = 0.96) and contralateral (F= 1.04) arms. Again, Student-Newman-Keuls' Hultiple Range Test was used t o find out which differences within groups were significant. The results indicated t h a t for each experimental group significant mean differences existed in both arms between the prc- and post-data a s well tls between the pre-and retention data. Although no significant differences was found between the post- and retention test data for Group I , the remaining three groups did experience significant decrements in both arms over their respective inactivity periods.

Conditioning and Deconditionil~gcm ~2u.scularStrength

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Discussion

4.1. Pre-Post Differences The difference between the pre- and post strength tests indicate that the traditional methods of progressive resistance weight training, utilizing isotonic contractions, will increase isometric elbow-flexion strength in the conditioned limb as well as in the unconditioned limb. The mean isometric strength improvement for the exercised arm during the developmental phase of the study was 12.6 per cent. The mean improvement for the unexercised arm was 8.9 per cent. No significant changes were found for the control group. These findings are in agreement with earlier investigators (Hellebrandt 1958, Hellebrandt and Houtz 1956, Hellebrandt et al. 1947, Houtz el nl. 1946, Shaver 1970) who have reported that, in general, an isotonic, overload-type of training will elicit muscular strength gains not only in the exercised limb, but also in the unexercised limb. 4.2. Pre-Betention Differences For all experimental groups, the findings between the pre- and retention strength data in both arms was statistically significant. This indicates clearly that each group did, in fact, retain a significant amount of the recently acquired strength in the conditioned as well as the unconditioned arm over the inactivity interval. No significant changes were found for the control group. These findings are in complete accord with the results of Miiller and Hettinger (1954), and Shaver (1973), all of whom found significant retention of muscular strength following different intervals of detraining. The percentages of the recently acquired isonlctric strength lost in the conditioned arm over the various rest periods were as follows: (a) 0.8 per cent following 1 week, (b) 2.0 per cent following 4 weeks, (c) 3.1 per cent following 6 weeks, and (d) 3.2 per cent following 8 weeks of detraining. These findings agree generally with those of Miillcr and Hettinger (1954), and Shaver (1973). Miiller and Hettinger found average decreases in strength t o be around 0.3 per cent per week following maximal isometric training. Shaver, in a later study, reported that rest periods of 3- and 5-weeks results in a significant loss of newly acquired isometric strength gains following 6 weeks of isotonic training in which the subjects improved their mean isometric strength by 8 per cent. In that investigation, the percentages of new isometric strength lost in the exercised arm were: ( a ) 0.5 per cent following a 1-week inactivity period, ( b ) 1.5 per cent following 3 weeks of inactivity, and (c) 2.5 per cent following a &week period of detraining. Although a detraining period of one week in the present study was not sufficient t o cause a statistically significant strength loss in the trained arm, i t would seem from the present results and also from Shaver's earlier research that there is a rather rapid drop-off between the 5th and 6th weeks following cessation of 6 weeks of training as employed in these studies. For example, approximately 3.1 per cent of the newly attained strength gains in the present study for the conditioned arm was lost after 6 weeks of inactivity, whereas Shaver's earlier work found that approximately 2.5 per cent was lost after 5 weeks of inactivity. It appears that after this relatively fast drop-off (between 5 and 6 weeks), absolute loss begins to subside much more slowly.

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Larry G. Shver

For instance, in the present study, there was only a n additional 0.1 per cent lost in strength after 8 weeks of inactivity as coniparecl t o the 3.1 per cent lost for the 6 weeks of inwtivity. 'I'he percentages of the newly acquired isometric strength lost in the unconditioned arm over the inactivity periods in the present investigation were as follo\vs: (a)0.5 per cent following 1 week, s b ) 1.3 per cent following 4 weeks, (c) 2.0 per cent following 6 weeks, and (d) 2.1 per cent following 8 weeks of tletn~ininy. Shaver's ( 1 973) earlier work found similar, but somewhat smaller linear decreases in strength for inactivity periods of I-, 3-, and 5-weeks following 6 weeks of isotonic training. Tn t h a t study, the percentages of new isometric strength lost iu the unconditioned arm were: (a) 0.7 per cent following 1 week of i~mctivity,(6) 1.0 per cent following 3 weeks of inactivity, and (c) 1.5 per ccnt following 5 weeks of inactivity. These results would suggest, in light of the prcsent study, t h a t a rapid drop-off in newly acquired levels of isometric strength in the unconditioned arm might occur between the 4th and 6th weeks following trr~ining. T t is interesting t o note t h a t after this initial quick dropoff (between 4 and 6 weeks), absolute loss begins t o decline much slowcr (a similar trend was noted for the conditioned &m between t h e 5th and 6th wccks). For instance, in the prcsent investigation, there was only an additional 0.1 per cent lost in strength after 8 week; of inactivity as compared t o the 2.0 per cent lost for the G wccks of inactivity. !l.'hc results of the present stndy as well as those from earlier research seem to itidicate that m extremely important factor which must be considered in c v ; ~ I ~ a t i nni~~sculnr g strength retention in the conditioned as well s s in the unconditioned limb is the amount of strength developed during the training programme p ~ w d i n gthe lay-off. For example, in Shaver's earlier study in which the subjects were trained for 6 weeks (using an arm-lever ergometer, isotonic-type training programme), they experienced average mean gains of only 8 per cent in the exercised arm and only 4 per cent in the unexercised arm. The subjects in the present investigation were also trained for 6 weeks (using ib progressive-resistaice, isotonic-type training programme) and experienced gains of 12.6 per cent for the conditioned arm and 8.9 per cent for the unconditioned :Lrm. Thus, the subjects in the present investigation gained nearly twice as much strength as did the subjects in Shaver's earlier experiment. 'I'herefore, i t would seem possible that perhaps the subjects in the present study may have come closer to their maximal possible attainment in isometric strength iincl consequently had available a greater amount t o be lost as was shown (Waltlman and Stull 1969). I n an earlier cardiovascular retention study, Applegate and Stull (1969) hypothesized t h a t the closer one comes t o his maximum possible endurance ;~tta;inment,thc greater is his absolute loss following cessation of training. Lt would appear that the same hypothesis could be stated for the present investigation. 'I'hat is, the closer one comes t o his maximum possible strength atti~inmcnt,the greater is his absolute loss following cessation of training. J t is apparent t h a t additional work is needed dealing with the nature of strength loss as well as the interaction between length of conditioning and strength decrements in the conditioned and also in the unconditioned limb following different periods of inactivity.

Conditioning and Deconditioning on Muscular Strength

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Conclusions

Within the scope of this study, the following conclusions can be made: ( I ) A G-week progressive-resistance, isotonic training programme caused significant increases in maximum isometric strength - of contralateral as well as ipsilateral muscles. (2) No significant amount of newly acquired isometric strength gains were lost in the conditioned as well as the unconditioned arm despite 1 meek of detraining. (3) Detraining of 4, 6 and 8 weeks resulted in a significant loss (average of 2.8 per cent) of newly acquired isometric strength gains in the conditioned arm and in the unconditioned arm (average of 1.8 per ccnt). However, scores were still higher than the pre-conditioning test indicating retention of some strength gains. L'objoctif do cctte experience Otait d'etudicr leu effects do perioden d'inactivitb do 1, 4, 6 e t 8 semaines rur l a persistonco de la force rnusculairo rOcernment acquise. Les sujets (80 pour la condition expbrimentale e t 20 pour la condition de r6f6rence) Btaient de sex0 masculin, tous droitiers, BgBs de 18 8. 22 ans. Los sujets d u groupe expi?rimental ont particip3 trois fois par semsine, pendant 6 sernaines b des sbanccs da conditionnernent pour un travail musculniro de force trbs intensif mais pou rBp6titif. AprBs cet ontrainemcnt, les sujets ant 6th repartis albntoiromcnt e n 4 g r o u p s expbri~nentaurqui arretaient l'cntrninement pendant 1, 4, 6 ou 8 sernaines. A la fin do ocs p5riodes d'inactivitb une Opreuve do retention a Btb admLustr6e aux deux bras. Los r6sultats ant rnontrb que tous leu groupcs exp6rimentaux ant significativement amelior6 la force iscntbtrique pour Ics deux hraa nu courr de I'entrainoment, ce qui d h o n t r c la phbnom&ne du trarufcrt contrelat6ral do la forcc isombtriquo. Aueunc diffbrenco significative n'est apparuc d a m lo groupe du r6f6renco. On a Bgnlcrnent montri: que toos les g r o u p s exp6rimontaux ont reteuu uno quantit6 significative 4e force isom6triquc dnns los deux bras, h la suite cles p6riodcs d'inactivitb. I1 n'y a eu aucunc perte significative do la forcc, auvsi bion d a ~ wlo bras conditionnB quo d a m Ic bras no11 c o n d i t i o ~ dapri.3 nrle semaiuc lie non-cntrainemont. Cependant I'arrbt de I'entrainement pendant 4, 6 e t 8 semaincs etait la cause d'une perte significative dnns Ies dcux bras. Enfin, aucunc diffbrence significative n'a Btb trouv6o entre Ies g r o u p s de 6 st do 8 somines d'inactivit6, aassi bien en ce qui concerne le bras entrain6 quc lo bras nor1 entrainb. Diese Untersuchung beabsichtigte, die Wirkung van Untiitigkeitsperioden van 1, 4, 6 und 8 Wochen auf die Erhaltung der Hohe kurz zuvor erworbener Muskelkriift im gleichseitigcn und gegenseitigcn Arm zu untersuchen. Die Versuchspersonen (80 fur das Experiment und 20 zur Kontrollc) waren rechtshiindigo miinnliche Freiwillige, 18 bis 22 jahre alt. Die untersuchten Personen nahmen dreimal wochentlich a n einom sechswochigen Hochintensiv-Konditionie. rungsprogramrn dor Muskelkraft n i t wenigon Wiederholungen teil. Nach dem Training -den die trainierton Personen willkurlich auf vier experimcntello Gruppen verteilt, welche das Training fiir 1, 4, 6 oder 8 Wochen unterbrachen. Nach Ahlauf der Inaktivitiitsperiode wurder bciclo Amte auf ihre Kraft-Erhaltung getestet. Die Daten-analyse zoigte, dass alle expcrimentellon Cruppen ihre isometrischen Krnftniveaus in beiden Armen wiihrend der Konditionierung signifikant erhohten. Sic demonstrierten somit das Phanomen des Vber-Kreuz-Traillings cler isometrischen Kraft. Bei don Kontrollgruppen wurden koine signifikanten Unterschiedegefumden. E s wurde weiter festgestcllt, dass alle experimentellen Gruppen einen signiiikanten Betrag der isomctrischen Kraftzunnhme nach don Inaktivitiitsperiodcm in beiden Armen zuriickbehielten. Trotz einer Wocho Inaktivitut wurde wedcr im konditionierten noch im unkoditionierten Arm eino signifikanter Retrag a m Kraft verloren. Innktivitiit iiber 4, 6 und 8 Wochen fiihrt dagegen zu einem signifikanten Vorlust in hoiclcn Armen. Schliesslich fandeu sich keine signifikanten Unterschiede zwischen den 6- und 8- \\'ochcn-Inaktivitiitsgruppen im konditionierten Arm so wenig wie unkonditionierten.

References AFFLEQATE,V. W., and STWIL, G . A., 1969, Effect of varied rest periods on c&diovasculnr endurance retention by college u.ornen. Amon'eot~ Correclive Therapy Joz~mal,23, 3-6 CLARKE,H. H., and CMHKE, D. H.. 1963, Deuelopmenlal a d Adapted Phyaical Education. (Englewood Cliffs, New Jersey: PRENTICE-HALL).

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Conditioning and Deconditioning on Muscular Strength

DAVIS,R. C., 1942, The pattern of muscular action in simple voluntary movement. Journal of Ezperiwbental Psychology, 81, 347-366. T.L., and WATKINY, A. L., 1948, Technics of progressive resistance exercise. Archiuen DELORME, of Physical Medicine, 29, 263-273. HELLEBWDT,F. A.. 1958, Application of the overload principle to muscle training in man. American Journul of Phyaical Medicine, 87, 278-283. HELLEBRANDT, F. A., 1951, Cross education ipsihteral and contralateral effects of unimanual training. Journul of Applied Physiology, 4, 136-144. HELLEBRANDT, F.A,, and Hourz, S. J., 1956, Mechanisms of muscle training in man: Experimental dernonatrationa of the ovcrlond principle. Physical Therapy Review, 36, 371-383. F. A,, PARRISH, A. & I . , and H o u ~ z S. , J., 1947, Cross education: The influence HEI.I.EBRANDT, of unilateral exercise on contralateral limb. Archiuen of Physical Medicine, 28, 76-85. HOIJTZ. 8. J.,Pmnrsn, A. M., and HELLEBRANDT, F. A,, 1946, The influence of heavy resistance exorciao on strength. Physiotherapy Review, 26, 299-304. MULT.ER,E. A,, 1970, Influence of training and of inactivity on muscle strength. Archiuw of Phyaiurl Medicine and Itelnzbilitation, 51, 449-462. T., 1954, Die bedeutung des trainingsverlaufs fur dio trainings&fiJLLER,E. A,, and HETPINOER, festigkcit von muskeln. Arbeitaphyaiologie, 15, 452458. MULLEII,E. A,, and H E ~ I N O E T., R , 1953, Uher unterschiede der trainingsgeschwindigkeit atrophierter ond normalor muskeln. Arbeitsphysiologie, 15, 223-230. Rnsca, P. J., and MOREHOUSE, L. E., 1957. Effect of static and dynamic exercises on muscular etmngth and hypertrophy. Jounurl of Applied Phyaiology, 11, 29-34. SCRIPTURE, E. W., SMITH.T. L., and BROWN,E. BI., 1894, On the education of muscular control and power. Studies of Yale Psychology Laboralmy, 2, 114-1 19. L. G., 1973, Cross transfer effects of training a n d detraining on relative muscular SHAVER, onduranco. American Cmeclive Therapy Journal. 27, 47-56. SHAVER,L. G., 1970, Effects of training on relative muscular ondurance in ipsilateral and contralateral nrms. Medicine and Science i n Sports, 2, 16.5-171. A. T., 1950, Bilateral effects of muscle activity. Renearch Quarterly, 21, SLATER-HAMMEI., 203-209. SYYLER, B. L;, and STULL,G. A,, 1970, Muscular endurance retention a s a function of length of dotminil%. Research Quarterly. 41, 105-100. \ V ~ r . n w ,R., and STULL,G. A,, 1969, Effects of varioG periods of'inactivity on retention of newly acquirml levels of ~nuscularendurance. liesearch Quurlerly, 40, 396401. WALSHE,P. M. R., 1923, Oncortain tonic or postural reflexes in hemiplogia, with special rcferonce to tho so-colled associated movements. Brain, 46, 2-37. W A L T E ~C., E., 19.55, The cffect of overload on bilateral transfer of a motor skill. Phyaical Therapy Review, 85, 567469. L. M.. 1958, Develop~nontof bilateral muscular strength through ipsilnteral exercises. WEI.LOCK, Phy8ical Therapy Review, 38, 671-675. WINER,B. J., 1962, Statistical Principled i n Ezperhentai D d g n (New York: MCGRAW-Hm).

Cross transfer effects of conditioning and deconditioning on muscular strength.

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