Academic Sports Scholar Vol. 2, Issue. 1, Jan 2013 ORIGINAL ARTICLE ISSN : 2277-3665 EFFECT OF GENDER DIFFERENCE AND CIRCADIAN RHYTHM ON FLEXIBILITY OF VOLLEYBALL PLAYERS I.RAJAGOPAL Physical Education Teacher AVT Municipal High School Sivakasi, Virudhunagar District, Tamilnadu, India Abstract: The purpose of the study was to determine if there are differences in gender and circadian rhythm that affect the flexibility of volleyball players. Thirty volleyball players (15 men and 15 women) between 19 and 22 years of age were randomly selected as subjects. The two independent variables of gender and circadian rhythm and the dependent variable of flexibility were evaluated. The experimental design used was a static group factorial design. The flexibility data were collected by using sit and reach test at 02:00, 06:00, 10:00, 14:00, 18:00 and 22:00 hours during the academic year of 2012-2013. The data were statistically analyzed using a two-way factorial (2 x 6) Analysis of Variance (ANOVA) and Cosinor analysis. There was a significant difference between genders, significant difference in different times of the day and significant circadian rhythmicity exists on flexibility. The study concluded that the variation in flexibility at different times of the day would have a large effect on the performance of volleyball players. It is recommended to the physical educators to adopt the findings of this study while planning to improve sports skills for the players and athletes. KEY WORD: Circadian Rhythm, Flexibility, Gender difference, Volleyball players, INTRODUCTION In human beings, a variety of physiological functions such as body temperature and heart-rate undergo distinct rhythmic changes in the 24 hour period. Generally the values are at their lowest during the night and reach their peak in the afternoon. This phenomenon is known as Circadian Rhythms [4]. A biological rhythm associated with the solar day, which has a period of approximately 24 h. Circadian rhythms have been demonstrated in humans for changes in heart rate, metabolic rate, wakefulness, and flexibility. Rectal temperature shows a distinct circadian rhythm with temperatures being at their lowest at about 4 a.m. and then increasing during the day to peak in the afternoon. Levels of sport performance also follow a circadian rhythm. Runners, cyclists, and swimmers tend to perform better in the afternoon and early evening than early in the morning for both aerobic and anaerobic activities of short to moderate duration. The peak probably corresponds to the time when body temperature is highest since muscles work better when warm. Fencers tend to perform best in the middle of the day, perhaps because their sport depends on mental skills, which peak about that time. Studies of endurance athletes have not revealed any clear circadian rhythm, although some endurance athletes peak later in the day. There appear to be Please cite this Article as : I.RAJAGOPAL, EFFECT OF GENDER DIFFERENCE AND CIRCADIAN RHYTHM ON FLEXIBILITY OF VOLLEYBALL PLAYERS : Academic Sports Scholar (Jan. ; 2013)
individual differences among athletes of all sports, with the phasing of circadian rhythms being affected by types [3]. One of the factors limiting sport performance in particular sports is a decreased range of motion in joints. Although game performance in volleyball does not exert extreme demands on flexibility, it is very important to develop an optimal range of motion in joints and related functions of individual muscles and muscle groups. A better understanding of movement system functions is one of conditions for cultivation and development of game performance in volleyball [9]. Generally circadian rhythms do affect the flexibility which is the key fitness factor for volleyball players. Gender differences also play a vital role in the flexibility of volleyball players. The purpose of the study is to determine if there are differences in gender and circadian rhythm that affect the flexibility of volleyball players. RESEARCH METHODS Thirty volleyball players [15 men and 15 women] between 19 and 22 years of age were randomly selected as subjects from various colleges in Virudhunagar District, Tamil Nadu, India. They were in a good state of fitness, and they regularly took part in physical activities and game practice both morning and evening during the 2012-2013 academic year. Men and women volleyball players were selected as one categorical variable. Circadian rhythms usually form sinusoid within a period about 24 hours. Six different times of the 24- hour day, 02:00 hours, 06:00 hours, 10:00 hours, 14:00 hours, 18:00 hours, and 22:00 hours were selected as another categorical variable. Flexibility was selected as the dependent variable. The flexibility data were collected using Sit and Reach Test during the six different times. STATISTICAL PROCEDURE The experimental approach consisted of a static group factorial design. The first factor consisted of gender status as men and women volleyball players. The second factor consisted of circadian variation measured at six different times of the day. Two factor analysis of variance with the second factor a repeated (2 x 6) measure to find out the influence of each of the factors independently and also their combined influence on the dependent variable of Flexibility. Three F values were computed; one for rows to assess the gender status on the dependent variable, and the second F-value was calculated for columns to assess the circadian variations on the dependent variable. The third F - value was calculated for gender status and different times of the day. If the obtained F - values were significant, the Scheffe's post-hoc test was used for columns to find out the significant difference if any among the paired means. If interactions were significant, the simple effect follows up technique was used for testing the differences among cells. Then, the Scheffe's test was used as a test of significant difference between each cell. The significant level was fixed at 0.05 levels. The mean value of each cell was subjected to cosinor analysis to find out the parameters of circadian rhythm, the percentage Rhythm with Probability level, the mesor value, the amplitude and Acrophase for flexibility in the men and women subjects. Circadian rhythm was considered statistically significant when p = 0.05. RESULTS The mean and standard deviation of flexibility of men and women volleyball players at six different times of the day are presented in Table 1. Status Table 1: Mean and Standard Deviation of Flexibility Mean ± Standard Deviation Times of the day 02:00 06:00 10:00 14:00 18:00 22:00 Mx Men 31.37 35.30 37.55 38.39 41.37 36.17 ± 2.43 ± 1.98 ± 2.16 ± 2.45 ± 2.02 ± 3.11 36.69 Women 35.37 37.77 40.25 42.11 46.47 41.38 ± 2.98 ± 2.28 ± 2.09 ± 1.90 ± 2.27 ± 2.67 40.56 My 33.37 36.54 38.9 40.25 43.92 38.78 (Flexibility scores are expressed in Centimeters.) Mx - Combined mean of men and women volleyball players irrespective of different times of the day. My - Combined mean of different times of the day irrespective of men and women volleyball players. 2
The mean values of male and female on flexibility are graphically represented in figure 1. FIGURE 1:MEAN SCORES OF FLEXIBILITY OF MALE AND FEMALE AT DIFFERENT TIMES OF THE DAY The data of flexibility have been analyzed by two factor ANOVA with repeated measures on the second factor and the results obtained are presented in Table 2. TABLE 2: Two Factor ANOVA With Repeated Measure Source of Variance Sum of Squares df Mean of Squares F- value Men and Women (Gender) 672.03 1 672.03 33.41* Error I 563.26 28 20.12 Different times of the day (Time) 1883.96 5 376.79 132.89* Interaction (Gender & Time) 50.10 5 10.02 3.53* Error II 396.95 140 2.84 *Significant at.05 level of confidence. (Table values required for significance at.05 level for df (1, 28) and (5, 140) are 4.20 and 2.28 respectively.) Table 2 shows that the F- value for factor A (Gender status - Men and Women volleyball players) is 33.41 and it is significant at.05 level of confidence as the required table value for significance is 4.20 (df 1 and 28). The 'F' value for Factor B (different times of the day) is 132.89 and it is significant at.05 level of confidence as the required table value for significance is 2.28 (df 5 and 140). The interaction F- value for Factor A X B (Gender status x different times of the day) is 3.53 and it is significant at.05 level of confidence as the required table value for significance is 2.28 (df 5 and 140). Since the obtained F- value for men and women volleyball players is significant, it has been concluded that there is a significant difference in flexibility between men and women volleyball players. The flexibility of men volleyball players (36.69 Centimeters) is lower than that of the women volleyball players (40.56 Centimeters). Women volleyball players have 3.87 Centimeters (10.55%) higher flexibility than that of the men volleyball players. The F- value obtained for six different times of the day is significant. It is therefore concluded that there is a significant difference in flexibility among six different times of the day. The difference between times of the day with flexibility is presented in Table 3. 3
Different Times of the Day Table 3: Scheffe s Test 02:00 06:00 10:00 14:00 18:00 22:00 Mean Difference 33.37 36.54 3.17* 33.37 38.90 5.53* 33.37 40.25 6.88* 33.37 43.92 10.55* 33.37 38.78 5.41* 36.54 38.90 2.36* 36.54 40.25 3.72* 36.54 43.92 7.38* 36.54 38.78 2.24* 38.90 40.25 1.35 38.90 43.92 5.02* 38.90 38.78 0.12 *Significant at.05 level of confidence. (Confidence interval value required for significance at.05 level is 1.47) 40.25 43.92 3.67* 40.25 38.78 1.47* 43.92 38.78 5.14* The results of the study clearly indicate that the flexibility differs as the time of the day varies and this difference in flexibility is found to be significant in 13 paired means out of compared 15 paired means. However, insignificant increase in flexibility is noted only in two paired means between 10.00 hours and 14.00 hours and 10:00 hours and 22:00 hours of the day. The difference in flexibility between 10.00 hours and 14.00 hours and 10:00 hours and 22:00 hours is not significant at.05 level of confidence. Hence it is concluded that among men and women volleyball players the flexibility variation depends on the times of the day. The results of the study indicate that there is a significant difference in the interaction effect [between rows (gender) and columns (different times of the day)] on flexibility. Since the interaction effect is significant, the simple effect test is applied as a follow-up test and the results are presented in Table 4. Table 4: Simple Effect Test Source of Variance Sum of Squares df Mean of Squares F - ratio Men and Women Volleyball players at 02:00 Hours 120.00 1 120.00 42.32* at 06:00 Hours 45.63 1 45.63 16.09* at 10:00 Hours 54.68 1 54.68 19.28* at 14:00 Hours 103.42 1 103.42 36.47* at 18:00 Hours 194.57 1 194.57 68.62* at 22:00 Hours 203.84 1 203.84 71.89* Men volleyball players at different times of the day Women volleyball players at different times of the day 841.69 5 168.34 59.37* 1092.37 5 218.47 77.05* Error 396.952 140 2.84 *Significant at.05 level of confidence (Table values required for significance at.05 level with df 5 and 140, & 1 and 140 are 2.28 and 3.84 respectively) 4
Table 4 shows that the F- values obtained for men and women at 02:00 hours, 6:00 hours, 10:00 hours, 14:00 hours, 18:00 hours, and 22:00 hours are significant at.05 level of confidence. Hence the men and women volleyball players have significant differences in the flexibility at all the selected different times of the day. The F- value obtained for men volleyball players at different times of the day (F = 59.37) and women volleyball players at different times of the day (F = 77.05) are significant at.05 level of confidence. It means that irrespective of the gender status; various times of the day significantly affect their flexibility. Hence Scheffe's test has been applied as the post hoc test of significance for men volleyball players at different times of the day and women volleyball players at different times of the day. The results of Scheffe's test for flexibility of men volleyball players at different times of the day have been presented in Table 5. Different Times of the Day Table 5: Scheffe s Test 02:00 06:00 10:00 14:00 18:00 22:00 Mean Difference 31.37 35.30 3.93* 31.37 37.55 6.18* 31.37 38.39 7.03* 31.37 41.37 10.00* 31.37 36.17 4.80* 35.30 37.55 2.25* 35.30 38.39 3.09* 35.30 41.37 6.07* 35.30 36.17 0.87 37.55 38.39 0.85 37.55 41.37 3.83* 37.55 36.17 1.38 *Significant at.05 level of confidence. (Confidence interval value required for significance at.05 level is 2.08) 38.39 41.37 2.98* 38.39 36.17 2.23* 41.37 36.17 5.21* The results of the post hoc analysis clearly indicate that there is a significant difference in flexibility of men volleyball players among different times of the day in 12 paired means out of compared 15 paired means. However, insignificant increase in flexibility is noted only in three paired means between 06:00 hours and 22:00 hours, 10:00 hours and 14.00 hours and 10:00 hours and 22:00 hours of the day. The difference in flexibility between 06:00 hours and 22:00 hours, 10:00 hours and 14.00 hours and 10:00 hours and 22:00 hours is not significant at.05 level of confidence. Hence it is concluded that among men volleyball players, the flexibility variation depends on the times of the day. Table 4 shows that 'F' value obtained for women volleyball players at different times of the day is 77.05 and it is significant at.05 level of confidence. Hence Scheffe's test has been applied as the post hoc test of significance and the results are presented in Table 6. 5
Table 6: Scheffe s Test Different Times of the Day 02:00 06:00 10:00 14:00 18:00 22:00 Mean Difference 35.37 37.77 2.40* 35.37 40.25 4.88* 35.37 42.11 6.74* 35.37 46.47 11.10* 35.37 41.38 6.01* 37.77 40.25 2.48* 37.77 42.1 4.34* 37.77 46.47 8.70* 37.77 41.38 3.61* 40.25 42.11 1.86 40.25 46.47 6.22* 40.25 41.38 1.13 42.11 46.47 4.36* 42.11 41.38 0.73 46.47 41.38 5.09* *Significant at.05 level of confidence. (Confidence interval value required for significance at.05 level is 2.08) The results of the post hoc analysis clearly indicate that there is a significant difference in flexibility of women volleyball players among different times of the day in 12 paired means out of compared 15 paired means. However, insignificant increase in flexibility is noted only in three paired means between 10:00 hours and 14:00 hours, 10:00 hours and 22:00 hours and 14:00 hours and 22:00 hours of the day. The difference in flexibility between 10:00 hours and 14:00 hours, 10:00 hours and 22:00 hours and 14:00 hours and 22:00 hours is not significant at.05 level of confidence. Hence it is concluded that among women volleyball players, the flexibility variation depends on the times of the day. Circadian rhythmicity of flexibility and its parameters are explored using the best fitting curve procedure. The mean value from the data is subjected to cosinor analysis and the results are presented in Table 7. Table 7: COSINOR Analysis of Circadian Rhythmicity Category Percent Rhythm Probability Level Mesor ± S.E Acrophase ± S.E Amplitude ± S.E % Amplitude of Mesor Men 78.50 0.100 36.69 ± 0.82 15:4 hours ± 1:15 hours 3.83 ± 1.158 10.44 Women 83.88 0.065 40.56 ± 0.81 16:6 hours ± 0:58 min 4.51 ± 1.142 11.13 The results of the cosinor analysis confirm the existence of circadian rhythm in flexibility for men volleyball players (78.50%) and women volleyball players (83.88%) which are statistically not significant (P >.05). The amplitude of the rhythm in men and women volleyball players is 3.83 and 4.51 respectively. 6
The time of peak performance (acrophase) in flexibility for men and women volleyball players is calculated by means of cosinor analysis to be 15:4 hours and 16:6 hours respectively. The mesor value (mean) for men and women volleyball players is 36.69 centimeters and 40.56 centimeters respectively. DISCUSSION ON FINDINGS The findings of the study show that there is a significant difference in flexibility between men and women volleyball players. Men volleyball players have less flexibility (36.69 cm) than women volleyball players (40.56 cm) and the difference is 7.87 cm (21.45%). This result confirms with the results of previous works of Hughes, et al., [5] who noted that females displayed significantly greater maximum valgus angle and range of motion than males. This result also supports the earlier findings of Emika Kato, et al., [1] who said that gender difference in the joint ROM at the ankle reflects more compliant Achilles tendon in women than in men. The result may be based on the reason reported by Nadya Swedan [8] that women are generally more flexible than men. Evidence for the difference appears in anatomical and physiological attributes. Depending on the type of pelvis they inherit, women with broader and shallower pelvis may have a greater range of motion in the hips. Women also have greater elbow extension because of a shorter upper area in the olecranon process than men. Women have smaller muscles than men. Smaller muscle cross-section means less passive resistance to stretch. So women have more flexibility than men. The study also reveals that there is a significant difference in mean flexibility among different times of the day irrespective of gender status. The mean flexibility is significantly higher at 18:00 hours (43.92 cm) than 02:00 hours (33.37 cm) with the difference of 10.55 cm (31.62%). This result supports the earlier findings of Thomas Reilly, et al., [10] who reported that diurnal variation was found for sit-and-reach flexibility and peaks occurred between 16:00 hours and 20:00 hours. This result also replicates the earlier findings of Jim Reeves Silent Night [7] who noted that a significant difference in mean flexibility among different times of the day and it is significantly higher at 15:43 hours. The result may be based on the reason reported by Jari Ylinen, Jari Juhani Ylinen, Leon Chaitow, Julie Nurmenniemi and Sandie Hill [6] that flexibility in the extremities and through the spine will change depending on the time of day. Stiffness gradually increases during sleep. Movement in the morning can feel stiff, but will improve with daily activity and improve more quickly with stretching. An increase in temperature will improve flexibility in the surrounding joint connective tissues and in general joint mobility. During sleep, energy requirements are low, circulation decreases and stiffness develop, especially in the distal joints where tissue temperature will drop the most. This is marked with conditions such as Raynaud's syndrome. So the higher flexibility at 18:00 hours may be due to the higher body temperature at evening (18:00 hours) and the prolonged vertical position of vertebral disk. The lower flexibility at 02:00 hours may be due to Raynaud's syndrome, lower body temperature at 02:00 hours and prolonged horizontal position of vertebral disk. The Simple Effect test followed by the Scheffe's post hoc test clearly indicates that the differences in flexibility of men volleyball players between selected different times of the day were significant except between 06:00 hours and 22:00 hours, 10:00 hours and 14:00 hours and between 10:00 hours and 22:00 hours. The mean flexibility of men volleyball players is significantly higher at 18:00 hours (41.37 cm) than at 02:00 hours (31.37 cm) with the difference of 10 cm (31.88%). The differences in flexibility of women volleyball players between selected different times of the day are significant except between 10:00 hours and 14:00 hours, 10:00 hours and 22:00 hours and between 14:00 hours and 22:00 hours. The mean flexibility of women volleyball players is significantly higher at 18:00 hours (46.47 cm) than at 02:00 hours (35.37 cm) with the difference of 11.1 cm (31.38%). The amount of variation between peak and trough values of flexibility of men volleyball players is (31.88%) higher than that of the women volleyball players (31.38%). Cosinor analysis shows that flexibility does confirm circadian rhythms for both the samples of men and women volleyball players but are statistically not significant. This result replicates Jim Reeves Silent Night's [7] earlier findings where statistically there were no significant circadian rhythms for both trained males and untrained males. The reason for the result may be due to their playing competition culture of the day and night tournaments. During the tournaments, both men and women volleyball players do the regular stretching exercises on warm up and warm down. So it may not be statistically significant in circadian rhythm in flexibility for men and women volleyball players. Men volleyball players have lower percentage rhythm in flexibility (78.50) than that of the women volleyball players (83.88). The rhythm amplitude of men volleyball players is lower (3.83) than that of women volleyball players (4.51). This contradicts the earlier findings of Giacomoni, et al., [2] who noted that males have more rhythm amplitude than females. 7
Men and women volleyball players have their peak performances on flexibility at 15:4 hours and 16:6 hours respectively which are a little bit earlier phase than body temperature phases. This supports the earlier findings of Thomas Reilly, et al., [10] who reported that diurnal variation was found for sit-and-reach flexibility and peaks occurred between 16:00 hours and 20:00 hours. The reason for the result may be based on the notion of William Garrett and Donald Kirkendall [11] that the portion of a spinal disc, nucleus pulposus, is made of a jelly like substance and consists of 88% of water. This soft part is surrounded by a tough outer covering, the annulus fibrosus. While in a vertical position, the spinal discs suffer loss of fluids and dehydration causes an increase in joint mobility. When the spinal discs are pressed together, the joint ligaments loosen, and mobility in the lumbar spin will increase by about 5% from morning to evening. An increase in temperature will improve flexibility in the surrounding joint connective tissues and in general joint mobility. So the flexibility may be peaking in the evening. CONCLUSIONS The purpose of the study is to determine if there are differences in gender and circadian rhythm that affect the flexibility of men and women volleyball players. The statistical findings indicate that there were significant differences in flexibility values between genders. However, there were significant differences at different times of the day. But, given that the size of the differences in flexibility is very big (10.55 centimeter), it is reasonable to conclude that the variation in flexibility at different times of the day would have a large effect on the performance of volleyball players or others planning to improve sports skills. The result of COSINOR analysis indicates that the best performance of flexibility is transpired in 15:4h and 16.6h for men and women volleyball players. The coach and sports trainer may utilize the results to prepare the sports schedule and training camp programmes. REFERENCES 1.Emika Kato Toshiaki Oda, Kentaro Chino, Toshiyuki Kurihara, Toshihiko Nagayoshi, Tetsuo Fukunaga and Yasuo Kawakami, Musculotendinous Factors Influencing Difference in Ankle Joint Flexibility between Women and Men, International Journal of Sport and Health Science, 2005 Special Issue; Vol. 3: 218-225. 2.Giacomoni, Magali, Edwards, Ben, Bambaeichi and Effat, Gender differences in the circadian variations in muscle strength assessed with and without superimposed electrical twitches, Ergonomics, 2005 September-November; 48(15): 1473 87. 3.http://www.answers.com/topic/circadian-rhythm 4.http://www.soccerperformance.org/specialtopics/circadjetlag.htm 5.Hughes G, Watkins J and Owen N., Gender differences in lower limb frontal plane kinematics during landing, Sports Biomechanics, 2008 Sep; 7(3): 333-41. 6.Jari Ylinen, Jari Juhani Ylinen, Leon Chaitow, Julie Nurmenniemi and Sandie Hill, Stretching Therapy. Netherlands: Elsevier Health Sciences Publisher, 2008. 7.Jim Reeves Silent Night D., Influence of Circadian Rhythms on Selected Physical, Physiological and Psychological variables, Unpublished Ph.D Thesis, Alagappa University, Karaikudi, 2003. 8.Nadya Swedan, Women's Sports medicine and rehabilitation. New York: Aspen Publication Inc, 2001. 9.Rostislav Vorálek, Miroslav Tichý and Vladimír Süss, Movement analysis related to functional characteristics of upper extremities in female junior volleyball players, International Journal of Volleyball Research, 2010, Volume 10 No. 1. Pp 7-13. 10.Thomas Reilly, Greg Atkinson, Ben Edwards, Jim Waterhouse, Kelly Farrelly and Emma Fairhurst, Diurnal Variation in Temperature, Mental and Physical Performance, and Tasks Specifically Related to Football (Soccer), Chronobiology International, 2007 May; 24 (3): 507 519. William E.Garrett and Donald T.Kirkendall, Exercise and sports science. Philadelphia: Lippincott Williams & Wilkins Publisher, 2000. 8