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SHORT COMMUNICATION  
Year : 2021  |  Volume : 14  |  Issue : 1  |  Page : 71-74
Association between hamstring flexibility and sprint speed after 8 weeks of yoga in male rugby players


1 Department of Tourism, Sport and Society, Lincoln University, Lincoln, New Zealand
2 Department of Tourism, Sport and Society, Faculty of Environment, Society and Design, Lincoln University, Lincoln, New Zealand

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Date of Submission12-Jul-2020
Date of Decision09-Sep-2020
Date of Acceptance22-Dec-2020
Date of Web Publication05-Feb-2021
 

   Abstract 

Background: A Yoga-asana-based intervention has demonstrated its ability to improve flexibility of individuals, but has not been explored in rugby players. We hypothesized that a structured yoga intervention may have an effect on flexibility and sprint performance in male rugby union players. Methods: It was a controlled trial research design and players were assigned using random sampling to one of the two groups; a yoga group (n = 16) that practised yoga for 1 h 2 times a week for 8 weeks in addition to their normal rugby training and a control group (n = 15) with regular rugby training but no yoga intervention. Yoga intervention included 32 yoga postures to address both the upper and lower extremities of the body. Data were collected during preseason and mid-season on hamstring flexibility (sit and reach test), and sprint performance (measured at 5, 10, and 30 m). Results: One hundred and twenty participants were screened and thirty-one players volunteered for the study. Interactions between groups and differences between pre- and post-intervention scores were analyzed using analysis of variance using SPSS (version 24.0). Significance was set at an alpha level of P = 0.05. The yoga group showed a small nonsignificant decrease (-1.2% ± 21.4%, P = 0.05) in hamstring flexibility compared to the control group which demonstrated a large significant decrease (-14.8% ± 23.7%) (mean % change ± 95% confidence interval [CI], P < 0.05). The yoga group also showed minor nonsignificant improvements in sprint times -3.2% ± 10.4%, -0.7% ± 9.0% for the 5 and 10 m sprints, respectively, (mean % change ± 95% CI) compared to controls -0.4% ± 10.2%, 0.4% ± 7.9%. Conclusions: Findings suggest that completing a structured yoga intervention alongside normal rugby training during the rugby season, yoga helped rugby players maintain their hamstring flexibility but did little to improve sprint performance during the season.

Keywords: Acceleration, performance, range of motion, stretching

How to cite this article:
Raj T, Hamlin MJ, Elliot CA. Association between hamstring flexibility and sprint speed after 8 weeks of yoga in male rugby players. Int J Yoga 2021;14:71-4

How to cite this URL:
Raj T, Hamlin MJ, Elliot CA. Association between hamstring flexibility and sprint speed after 8 weeks of yoga in male rugby players. Int J Yoga [serial online] 2021 [cited 2021 Mar 5];14:71-4. Available from: https://www.ijoy.org.in/text.asp?2021/14/1/71/308743



   Introduction Top


Flexibility is a vital factor that has been associated with improved performance[1] and reduced sports-related injuries.[2] Many coaches, physicians, and trainers have accepted the important role flexibility plays in sports and have included exercises to increase and maintain flexibility in warm-up sessions before sports activity.[1] However, researchers have reported mixed results when examining the effects of flexibility on speed, athletic performance, and countermovement jump performance.[1],[3],[4],[5],[6] These mixed results have created confusion and debate among researchers, particularly around the association stretching has with subsequent explosive performance.[4],[7],[8],[9] To date, only a few researchers have explored the chronic effect of a stretching routine or flexibility intervention on rugby players.[10]

Yoga is a combination of physical postures (Asana), breathing exercises (Pranayama), and meditation (Dhyana), which focuses on the physical and mental aspects of an individuals' movements.[11] Improved flexibility is one of the major benefits of yoga practice and yoga has been shown to have similar effects compared to stretching exercises.[12] This study employed Hatha-yoga, which uses various body positions to stretch muscles in conjunction with an emphasis on controlled breathing exercises.

The aim of the study was, therefore, to assess whether a yoga (stretching) intervention practised by male rugby players alongside their usual rugby training had any effect on their subsequent flexibility and sprint performance.


   Methods Top


Participants

Initially, 120 players were screened, and 31 male rugby players (19.5 ± 0.9 years) [Table 1] from a local rugby union football club volunteered for the study [Figure 1]. However, only nineteen players (yoga n = 12) (control n = 7) completed the study due to injuries and personal circumstances. All players were novices to the practice of yoga. Players were randomly assigned either to the yoga group (practised yoga for 1 h, two times/week for 8 weeks in addition to their normal rugby training) or the control group (continued with their normal rugby training without yoga). All players were free from any current or previous injuries. All players were also informed about the possible risks of volunteering for this study and provided written informed consent before the study. Following the Declaration of Helsinki, this research was approved by the Institutional Human Ethics Committee.
Table 1: Physical characteristics and playing experience of the yoga and control groups

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Figure 1: Flowchart describing the selection and categorisation of subjects from the rugby clubs for the present analysis

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Design of the study

A yoga intervention was exclusively designed for rugby players and delivered by a yoga instructor (registered exercise professional, New Zealand). Players were required to complete 3, 30 m sprints to measure the physical performance. All participants were in the same yoga class, and all sessions were completed in a large open fitness room.

Assessment

Flexibility of the hamstrings

A baseline examination was carried out 1–2 weeks before the yoga intervention and again 1–2 weeks after the last yoga session. The hamstring flexibility of players was measured in a seated position in front of a Flex-Tester© box (Novel Products, Inc.; Rockton, IL, USA). The hamstring flexibility test consisted of 3 sit-and-reach tests. Players were not allowed to flex their knees during the test and players were required to have a 2 min rest between each attempt with the best attempt used in the analysis.

Sprint performance

After completing the hamstring flexibility test, sprint performance was measured using three 30-m sprints. The sprint was analyzed in two acceleration phases (5 and 10 m) and maximal velocity (30 m).[13] Each participant completed the sprint from a standing start position. Sprint time (to the nearest 0.01 s) was recorded using a set of electronic speed-timing lights placed at 5, 10, and 30 m (SmartSpeed, Fusion Sport Ltd., Australia). A 2 min recovery was required between each sprint, and the best of 3 attempts was used in the analysis. All players were asked not to perform any strenuous exercise in the 24 h before testing. The testing was completed at the same time of day on a large covered slip-free floor area under similar climatic conditions.

Intervention

Yoga classes were offered two times a week for 8 weeks, which started at the beginning of the rugby season. The average attendance rate for the yoga group was 75% (12 sessions), with some players attending all (16) sessions, whereas others only attended (9) sessions. Each yoga session consisted of a warm-up of 10 min with Surya-namaskar (dynamic stretching sequence of postures) followed by 35 min of yoga postures (10 min standing, 10 min sitting, and 15 min of supine and prone postures and a mix of static and dynamic postures) and 10 min relaxation in the final resting position (lying in the supine position without any stretching exercise). A total of 5 min was allocated for the transition between the yoga postures.

Data extraction

The mean of the fastest sprint time and highest flexibility scores of individual players at pre- and post-testing were recorded on Excel and later were used in the group analyses.

Data analysis

The number of participants required for the study was calculated using a spreadsheet with the smallest worthwhile change in performance being 1.0% and the typical error or within-subject standard deviation (SD) in similar tests of 0.7%. This calculation estimated we needed 7 participants in each group in a controlled trial research design. Interactions between group and differences between pre- and post-intervention scores were analyzed using analysis of variance. Statistical analyses were performed using SPSS 24 for Windows (SPSS, Inc., Chicago, IL, USA). Significance was set at an alpha level of P = 0.05. Data given represents the mean ± SD unless stated otherwise.


   Results Top


The yoga group showed a small decrease (-1.2% ± 21.4%) in hamstring flexibility compared to the control group which demonstrated a significant decrease (-14.8% ± 23.7%) (mean % change ± 95% confidence interval [CI], P < 0.05). In addition, the yoga group showed a small, but nonsignificant improvement of 3.2% ± 10.4, and -0.7% ± 9.0%, in their sprint time when compared to the control group –0.4% ± 10.2%, 0.0% ± 7.9%, in 5 and 10 m, respectively [Table 2].
Table 2: Hamstring flexibility and 5, 10, 30 m sprint time of the yoga and control group

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   Discussion Top


This study found that rugby players that undertook 8 weeks of static and dynamic stretching during a weekly 1-h yoga intervention, in addition to their normal rugby training sessions, either maintained or had a minimal decrease in their hamstring flexibility compared to players who did the rugby training only. However, this flexibility training through the yoga intervention did little to improve short sprint performance between the groups (e.g., 5, 10, and 30-m sprint time), we found no significant beneficial improvement in sprint performance in the experimental group (receiving yoga intervention) compared to controls.

The controversial issue of stretching to improve performance is based on several postulated mechanisms. Dynamic movement requires the contraction and elongation of the muscle-tendon unit (and thereby, movement of the limb around the joint). This shortening and stretching (stretch-shortening cycle), relies on the elastic proprieties of the tendon to enable the release of potential energy. Hence, the elastic property of the muscle-tendon unit is crucial and is influenced by the stiffness of both tissues. It is believed that greater compliance (i.e., less stiffness) in these tissues improves energy storage, thereby enhancing muscle performance.[14] Given that the stretching (yoga) group improved flexibility, compared to the control group, which may have increased muscle compliance, this did not seem to change muscle performance during sprinting in the rugby players measured in this study. This suggests that either tissue compliance did not change (and the relative increase in flexibility is due to other mechanisms), or that there is little effect of increased compliance on sprint performance. On the other hand, while the yoga group showed an increase in flexibility compared to the control group (an average of 17.3%), in reality, the significant change between groups is probably because the flexibility in the control group decreased (-14.8%) while the flexibility in the yoga group changed little (-1.2%). Therefore, if the flexibility did not change in the yoga group, we would not expect to find greater muscular compliance and thus little change in performance.

Previous research has found that yoga practiced for 75 min two times/week for 20 weeks (average of 150 min/week) improved sit and reach scores by approximately 13 cm in the first 10 weeks and 17 cm at the end of training in healthy adults.[15] The players in the current study completed approximately 90 min/week for 8 weeks which may indicate a larger stretching dose is required to achieve significant flexibility changes. In addition, not all players in the current study made every yoga session with an attendance rate of only 60% compared to 78% in the Petric's[15] study. Overall, this would suggest the players in the current study received substantially less muscle stretching time which resulted in a lower stretching dose and therefore less muscle adaptation. We would recommend that any future studies in this area should allow players to complete at least 150 min of yoga per week. Whether the 150 min per week of muscle stretching (for a minimum of 12 and up to 20 weeks) can successfully be incorporated into shorter sessions (e.g. 30 min on 5 days/week) requires further investigation.

It is also possible, that due to muscle damage suffered either at training or during a match, which can result in substantial swelling and edema,[16] the effectiveness of any chronic stretching intervention, was reduced. We speculate that perhaps the stretching employed in the current study by the yoga group was enough to buffer any losses in sprint performance associated with such muscle damage since the yoga group sprint times did not decrease as much as the control group sprint times. However, this is speculative and would require further research before this theory can be confirmed.


   Conclusions Top


Yoga practiced for 1 h twice a week over an 8-week period was sufficient enough to maintain hamstring flexibility in male rugby players compared to players that did not complete yoga; however, the maintenance of flexibility did not result in any significant improvement in sprint performance in these players. We would recommend that any stretching intervention (including yoga) should be practiced for at least 150 min/week over a longer period (i.e., 20 weeks) to allow adaptations to occur which may result in muscular performance change.

Acknowledgment

We would like to thank the coaches and participants of the study for their time.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.



 
   References Top

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Fletcher IM, Anness R. The acute effects of combined static and dynamic stretch protocols on fifty-meter sprint performance in track-and-field athletes. J Strength Cond Res 2007;21:784-7.  Back to cited text no. 1
    
2.
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Yuktasir B, Kaya F. Investigation into the long-term effects of static and PNF stretching exercises on range of motion and jump performance. J Bodyw Mov Ther 2009;13:11-21.  Back to cited text no. 3
    
4.
Paradisis GP, Pappas PT, Theodorou AS, Zacharogiannis EG, Skordilis EK, Smirniotou AS. Effects of static and dynamic stretching on sprint and jump performance in boys and girls. J Strength Cond Res 2014;28:154-60.  Back to cited text no. 4
    
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Sayers AL, Farley RS, Fuller DK, Jubenville CB, Caputo JL. The effect of static stretching on phases of sprint performance in elite soccer players. J Strength Cond Res 2008;22:1416-21.  Back to cited text no. 5
    
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Skaggs JR, Joiner E, Pace J, Sini M, Skaggs D. Is flexibility associated with improved athletic performance? J Sci Med Central 2015;21:1010.  Back to cited text no. 6
    
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Shrier I. Does stretching improve performance? A systematic and critical review of the literature. Clin J Sport Med 2004;14:267-73.  Back to cited text no. 7
    
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Gleim GW, McHugh MP. Flexibility and its effects on sports injury and performance. Sports Med 1997;24:289-99.  Back to cited text no. 8
    
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Fletcher IM, Jones B. The effect of different warm-up stretch protocols on 20 meter sprint performance in trained rugby union players. J Strength Cond Res 2004;18:885-8.  Back to cited text no. 9
    
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Darrall-Jones JD, Jones B, Till K. Anthropometric and physical profiles of english academy rugby union players. J Strength Cond Res 2015;29:2086-96.  Back to cited text no. 10
    
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Brunelle JF, Blais-Coutu S, Gouadec K, Bédard É, Fait P. Influences of a yoga intervention on the postural skills of the Italian short track speed skating team. Open Access J Sports Med 2015;6:23-35.  Back to cited text no. 11
    
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Gothe NP, McAuley E. Yoga is as good as stretching-strengthening exercises in improving functional fitness outcomes: Results from a randomized controlled trial. J Gerontol A Biol Sci Med Sci 2016;71:406-11.  Back to cited text no. 12
    
13.
Darrall-Jones JD, Jones B, Till K. Anthropometric and physical profiles of english academy rugby union players. J Strength Cond Res 2015;29:2086-96.  Back to cited text no. 13
    
14.
Wilson GJ, Elliott BC, Wood GA. Stretch shorten cycle performance enhancement through flexibility training. Med Sci Sports Exerc 1992;24:116-23.  Back to cited text no. 14
    
15.
Petric M, Vauhnik R, Jakovljevic M. The impact of hatha yoga practice on flexibility: A pilot study. Altern Integr Med 2014;3160:2-10.  Back to cited text no. 15
    
16.
Järvinen TA, Järvinen M, Kalimo H. Regeneration of injured skeletal muscle after the injury. Muscles Ligaments Tendons J 2013;3:337-45.  Back to cited text no. 16
    

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Correspondence Address:
Tilak Raj
P.O. Box: 85084, Lincoln 7647, Canterbury
New Zealand
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/ijoy.IJOY_79_20

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