Effects of explosive and flexibility training in physical performance of ballet students between 7 to 10 years
Pereira, A, 1,2; Fraguito, M, 3; Costa, AJ. 4,2; João, PV. 3,2
1
Department of Science and Technology, Polytechnic Institute of Setubal, Portugal
2
Research Centre for Sport, Health and Human Development, Vila Real, Portugal
3
Department of Sport Sciences, Exercise and Health, University of Trás-os-Montes and Alto Douro, Vila
Real, Portugal 4
Department of Sport Sciences, University of Beira Interior, Covilhã, Portugal
Corresponding author Ana Pereira Technology and Science Department Polytechnic Institute of Setubal, Setubal, Portugal 2910-504 Setúbal Tel +351265710866
[email protected]
Abstract Strength and flexibility training has a strong effect in technical aspects in classical dance to achieved perfection and excellence of the classic lines. The purpose of the study was to examine the effects of 8 weeks of strength and flexibility training in muscle power in lower limbs [(CMJ and SJ (countermovement jump and squat jump)], muscle strength in upper limbs (push-ups of arms) and total body flexibility in Classical ballet students between 7 and 10 years. Twenty-four students and practitioners of ballet were divided into an experimental or control group [(GE, n=14; 7.3 ± 1.03 years; 1.3 ± 0.08 m; 26.5 ± 5.3 Kg and 16.58 ± 1.7 BMI and GC, n=10; 8.5 ± 1.5 years; 1.3 ± 0.09 m; 34.2 ± 8.7 Kg and 18.58 ± 2.6 BMI)]. The experimental group was submitted to a explosive strength training that consisted of multiple jumps and push-ups of arms exercises performed by 3 sets of 10 reps up until 3 sets of 4 reps in the end of the 8 week period. In the final of each session, it was also included exercises for flexibility (upper and lower limbs). Over the 8-week training period the EG significantly increased in all variables (7.5% to 95%, P˂0.05), except for the flexibility in the left and right arm (P=0.056 and P=0.870). In young students, the ballet lessons tend to be more effective in power and flexibility in lower limbs. The results of this study indicate that addition of high-intensity explosive training to regular dance practice increases power and flexibility especially in lower limbs. Keywords: Flexibility, Strength, Classical Ballet, Young Female.
Introduction Ballet is a very complete activity that concerns both physically and mentally tasks (Angioi, Metsios, Koutedakis, & Wyon, 2009; Javed, Tebben, Fischer, & Lteif, 2013). Teaching classical dance is based essentially on the comprehensive training of a variety of exercises to obtain the technical perfection. Classical ballet applying the five positions of the feet and the turnout of the legs (high-intensity intermittent exercise) mostly designed to improve movement technique (Kiefer et al., 2013; Lin, Lin, Hsue, & Su, 2013). In female athletic performance, the positive effects of exercise on health have become evident. However, with this growth in sports activity, a set of health problems unique to the female athlete has emerged as dysfunction related to energy availability, menstrual function, and bone mineral density (Ekegren,
Quested, & Brodrick, 2013; Ferrari, Silva, Martins, Fidelix, & Petroski, 2013; O'Neill, Pate, & Beets, 2012. Besides, weight training exercises have been reported to have positive effects on skeletal health. Evidence that exercise with higher loads may effectively stimulate osteogenesis has generated interest in plyometric exercises. Several researchers suggest that training based solely on dance does not provide adequate stimuli for the enhancement of muscle performance (Lee, Lin, Wu, Wu, & Lin, 2012; Ramel, Thorsson, & Wollmer, 1997; Widdop, 1968). In this way, it is well establish in literature that strength and flexibility has a strong effect in the classical dance training. Only with these capacities achieved it is possible to attained perfection and excellence of the classic lines. Training both capacities should constitute one of the goals of the modality, which is well described by great amplitude of movement through which upper and lower limbs are able to move (Angioi, Metsios, Koutedakis, & Wyon, 2009). Further, the type of exercise that are most performed in ballet consisted in explosive movements, as jumps and skills predominantly executed by power in the legs and/or arms. Thus, according to the characteristics of ballet, the training of the total body segments requires the development and the use of different methodologies in order to provide to young practitioners, new experiences as well as the acquisition of a physical fitness capacity conducive to the improvement of total performance. This investigation has importance given that we are finding that targeted interventions specific to this age group and gender that have greater value than a one size fits all model in classic ballet. Understanding the use of explosive training program in young student’s practitioners of ballet is an important task for this relatively unstudied age group. The purpose of this study was therefore to examine the effect of a 8-week explosive and flexibility training program for muscle power development in young female students. We hypothesized that a higher velocity developed in each exercise in this population could be highly effective in promoting significant changes in power and flexibility in upper and lower limbs.
Material & methods Participants Twenty-four young female students were divided into two groups (hereafter EG and CG): the experimental (EG, n=14; 7.3 ± 1.03 years; 1.3 ± 0.08 m; 26.5 ± 5.3 Kg and 16.58 ± 1.7 BMI) practitioners of ballet and the control (CG, n=10; 8.5 ± 1.5 years; 1.3 ± 0.09 m; 34.2 ± 8.7 Kg and 18.58 ± 2.6 IMC).
Efforts were made to recruit subjects so as to form comparable groups. All of the students were a part of a nursery-day-care center. Apart from routine daily tasks, the experimental group (EG) underwent a resistance training program of two training sessions per week over 8 weeks. The control group did not undergo any specifically orientated physical activity. None of the participants had a history of strength training. A written informed consent was obtained from each parent of the participants that were fully informed about the protocol before participating in this study. Further, the Direction of the High School was informed about the main goal of the study. The research study was approved by the local health services research ethics committee and was carried out according to the declaration of Helsinki. Testing procedures The evaluation process requires reliability, specificity and facility of application, especially when subjects are inexperienced. We thus selected protocols that were time-economical and that had been previously used in several studies for the assessment of musculoskeletal function in young people (Santos, Marinho, Costa, Izquierdo, & Marques, 2011). All testing procedures were applied to both groups before the experimental period (T1) and after 8 weeks of training (T2). Testing (T1 and T2) took place over a period of three days (three sessions separated by 3 to 5 days), always in the same location and time and supervised by the same researchers. In the first session, all subjects were assessed on anthropometric factors: weight and height. The second session (3 days later) involved measures of power and strength (vertical jumps and push-ups of arms). Before testing, each subject was familiarized with all strength testing procedures, preceded by a general warm-up routine. Verbal encouragement was given throughout the voluntary test and biofeedback provided in order to maximize motivation. Anthropometric measures Total height (m) and body weight (kg) were assessed according to international standards for anthropometric assessment (Pereira et al., 2013). To evaluate height (cm) a stadiometer (SECA, model 225, Germany) with a scale range of 0.10 cm was used and body mass (kg) was measured to the nearest 0.1 kg using a digital scale (Philips, type HF 351/00). These parameters were assessed prior to any physical performance test. Subjects were tested whilst wearing shorts and t-shirts (shoes and socks were removed).
Shoulder Flexibility The goal was to touch the fingertips of both hands behind the back. This test began with the participant standing back towards the teacher. To evaluate the right shoulder, the student should reach the middle of the back with his right hand over his right shoulder and simultaneously the left hand should be placed behind the back, trying to reach the fingers of his right hand. To evaluate the left shoulder, the participant ran the same movement with the left hand on the left shoulder, while the right hand should touch the fingers of the left hand. The final result was considered in centimeters (cm) to both sides, being negative when the participant did not reach the opposite hand and positive when exceeded. Sit and reach test modified Evaluate the flexibility of flexion of the trunk in front, from a sitting position with both legs taking together and extended. The test was applied using a box with a height of approximately 30 cm flat and vertical. In the most distal tip of the fingers is placed the “zero” of the ruler, which must remain motionless until the end of the test. The final result is the most distal tip stricken distance of fingers of the performer. The average maximum height of three trials was adopted and expressed in centimeters (cm) for further analysis. Strength tests The goal was to perform the largest number of arms extensions with a specific cadence (20 per minute, one repetition for each 3 seconds). This test began with the participant in ventral decubitus position on the mattress by placing the hands under the shoulders, fingers and the lower extremities in extension. To perform the participant execute force in the arms to be extended, then flexion the upper limbs until the elbows forming a 90º angle. The test is over when the participant stopped or completes an incorrect execution. The total of correct extensions was accounted for analysis. Power tests Dynamic explosive force characteristics of the leg muscles were measured using a trigonometric carpet (Ergojump Digitime 1000; Digitest, Jyvaskyla, Finland). Maximum height was assessed in countermovement jump (CMJ) (Pereira et al., 2012): each subject started from an erect standing position and the end of the concentric phase corresponded to a full leg extension (180°), and was also assessed for squat
jump (Häkkinen et al., 1998): from a starting position of 90° for the knee angle, the hands were kept on the hips during the jump. Each test was performed three times, each separated by a 2-minute rest period. The average maximum height of three trials was adopted and expressed in centimeters (cm) for further analysis. The height of rise of the center of gravity in the SJ was calculated from the flight time, and power was analyzed from the vertical force-time curve. In all tests, external verbal encouragement was given for each subject. Explosive training protocol The training program consisted of two sessions per week over 8 consecutive weeks. The RT program was supervised by one resistance training specialists to ensure that the participants correctly followed the training schedule. The control group was permitted the same recreational and social activities as the experimental group. After 45 minutes of ballet lesson (Ballet program of Royal Academy of Dance), the explosive training was initiated. Subjects performed two power exercises: lunges, the counter movement jump and squat jump, 3 sets of 10 reps up until 3 sets of 4 reps in the end of the 8 week period. In each session, they also performed exercises for flexibility of the upper and lower limbs (3 sets of 3 reps, 20 seconds each, in maximum amplitude). Rest intervals of 2 min between sets and 3 min between exercises were deployed. The training protocol was conducted every Monday and Wednesday (19:00 a.m.), throughout the 8 weeks of training. The subjects did not undertake any additional formal strength training activities during the testing or training period. Each session lasted for approximately 60 min including the warm-up period. Statistical analysis Standard statistical methods were used for the calculation of means and standard deviations. The normality and homoscedasticity assumptions were checked respectively with the Shapiro–Wilk and the Levene Tests. The training-related effects were assessed using two-way ANOVA with repeated measures (groups × time). Results were significant in the interaction (P ≤ 0.05). A t-test for independent samples determined the differences between the groups. Probability-adjusted Student's paired t-test was used for pair-wise comparisons. Test–retest reliabilities, as showed by ICC, ranged from 0.89 to 0.93 for all testing
exercises. Statistical significance was accepted at p ≤ 0.05 for analysis. All data were analyzed using SPSS 17.0. Results There were no significant differences (p>0.05) observed between groups for anthropometric, strength, power performance or flexibility variables at the beginning of the protocol. No significant changes (p>0.05) in height, weight or BMI were observed between first (T1) and second evaluation (T2) in both control and experimental group. From pre- to post-training period, the EG significantly increased their dynamic strength performance in push up of arms, SJ, CMJ (95%, 15.2% and 7.5%, p=0.008, p=0.005 and p= 0.003 respectively) and flexibility, mainly in flexibility in the legs, 83.8%, p=0.001, whereas no significant changes were observed for the CG (−5.9% 20%, p˃0.05) (table 1). Nevertheless, the training effect in EG do not increased shoulder flexibility in both arms (in the right and left side) (p=0.056 and p=0.87). Table 1. Mean±standard deviation values regarding the subject's anthropometric characteristics.
Variables
T1
T2
x±σ
x±σ
GC (N=10)
1,5 ± 4,5
1,5 ± 4,1
GE (N=14)
1,8± 3,8
1,9 ± 3,8
GC
1,0 ± 2,3
0,8 ± 4,5
GE
1,4 ± 3,0
1,6 ± 3,3
GC
-2,91 ± 8,0
-3,5 ± 8,1
GE
3,1 ± 3,4
5,7 ± 3,9*₮
GC
36,2 ± 3,8
36,4 ± 3,4
GE
37,5 ± 8,1 43,2 ± 6,6*₮
GC
38,9 ± 4,2
GE
39,3 ± 4,7 42,3 ± 3,2*₮
GC
9,5 ± 4,5
Group
Flexibility in the Right Arm (cm)
Flexibility in the Left Arm (cm)
Flexibility in the Legs (cm)
SJ (cm)
36,6 ± 4,6
CMJ (cm)
Push up of Arms
10,0 ± 4,3
GE
11,0 ± 6,2 21,5 ± 7,2*₮
Legend: Values are means (±SD). ₮Significantly different (p
