EFFECTS OF 6-WEEK PRE-SEASON PLYOMETRIC TRAINING TO PERFORMANCE CHARACTERISTICS IN FEMALE HANDBALL PLAYERS

The purpose of this study was to examine the effects of a 6-week pre-season plyometric training on the performance characteristics in female handball players. Nineteen female handball players voluntarily participated in the study. They were divided into 2 groups [experimental group (ETG; N = 10), and control group (NTG; N = 9)]. Both groups continued regular pre-season training for 6-weeks. The ETG also did plyometric training. Sprints (10 m, 20 m, and 30 m), squat jump (SJ), countermovement jump (CMJ), anaerobic power and capacity (AP and AC), and aerobic variables at fixed blood lactate levels (FBLLs) [running velocity (RV), heart rate (HR), and oxygen consumption (VO2)] were compared before and after the training. The results have shown that there are significant differences in SJ and CMJ (p<0.05), all sprints (p<0.01), AP and AC (p<0.05), VO2max (p<0.01), RV, HR, and VO2 at each of FBLLs (p<0.01) between preand post-training results of ETG. Preand post training results also showed significant differences in SJ and CMJ (p<0.05), all sprints (p<0.01), and AP (p<0.05) in NTG. In conclusion, was found that a 6-week plyometric training is an important parameter in addition to physical fitness, technical, and tactical training for the female handball players who get prepared for the woman handball super league which affects pre-season performance charecteristics.


INTRODUCTION
Handball is one of the sporting activities involving a great amount of body contact among players and various lower extremity movements such as starts, stops, jumps, landings, rapid changes in moving directions, repeated accelerations, and sprints, which provoke high mechanical stress on lower extremity due to high ground reaction forces and different upper extremity movements like throwing, fall landings, and ball blocks (Vicente-Rodrigueza, Doradoa, Perez-Gomeza, Gonzalez-Henriquezbi, & Calbet, 2004; Ronglan, Raastad, & Børgese, 2006; Cavala, & Katic, 2010; Massuca, Fragoso, & Teles, 2014; Karcher, & Bucheit, 2014; Wagner, Finkenzeller, Wurth, & von Duvillard, 2014).These movements put a lot of strain on different muscles and develop degrees of fatigue, which entails a certain amount of recovery time to re-store normal performance level (Ronglan et al, 2006).Handball players who are exposed to heavy load in training should present high levels of strength, muscle power, sprint and endurance running (Granados, Izquierdo, Ibanez, Bonnabau, & Gorostiaga, 2007).It has been shown that handball performance can be improved by specific handball conditioning with complex resistance, sprint, and endurance training in addition to technical training (Jensen, Jacobsen, Hetland, & Tveit, 1997).Complex training is necessary for rapid, explosive and powerful muscle contraction ability for handball players.Adaptations to these complex trainings are total changes as a result of regular workouts.However, optimal way and the relative effects of specific training for performance are little known.Gorostiaga et al (Gorostiaga, Granados, Ibanez, Gonzalez-Badillo, & Izquierdo, 2006) have found significant relationships between muscle power output of the upper and lower body extremities related to strength training and high-intensity endurance training during the full training season in elite handball players.Examination of training effect could be of a great importance for the optimal construction of the physical and sport-specific conditioning programs to improve handball performance (Jensen et al., 1997).When physical conditioning, technical and tactical practices in handball are good enough to provide adequate stimuli, particularly for muscle strength enhancement, physical performance could be improved in women handball players.Physiological and bio-motor characteristics are specified and training programs are planned with respect to these characteristics in the scope of these training programs utilizing sports performance tests in track and laboratory conditions.
It is possible to determine physiological changes reasoning by plyometric training, to identify physical status of athletes after plyometric training, and to revise the performance status of athletes having potential for a new training phase.Evaluation of sprint, jump, anaerobic power-capacity, and muscular strength reveal important details about training status of women handball players.From this point, there were no studies investigating handball conditioning parameters monitored over the training phases and the quantitative assessments of training and competition in elite female handball players.Therefore, the aim of this study was to examine the effects of a 6-week pre-season plyometric training on the performance characteristics in female handball players.

Participants
Nineteen-female handball players from the Super Laegue Team voluntarily participated in the study.All subjects performed regular strength/power training at least three times a week for a minimal period of 4-years.They were divided into ETG (age: 20.4 ± 3.0 years, height: 170.7 ± 5.5 cm, weight: 65.8 ± 8.3 kg) and NTG (age: 19.4 ± 3.3 years, height: 172.6 ± 3.9cm, weight: 66.6 ± 9.1 kg).A written informed consent was obtained from each subject to participate in the study in accordance with the ethical standards of the Helsinki Declaration.The study was approved by the Ethical Committee of Osmangazi University.

Training Period
Both groups were trained for 6-weeks in physical fitness, technical training (TE) and tactical training (TA), and training game (TG) for the pre-season (Table 1).Each week included 5

Sprint Tests
The handball players performed sprints (10 m, 20 m, 30 m) on an indoor synthetic track.Each sprint was recorded by customized Precision Timing System (PTS) (MP501, Tümer Electronic Ltd, Turkey).Photocells of PTS were adjusted to trochanter height to standardize the cutting point of infrared light.The players commenced the sprint when they are ready on a standing start 1m behind the first photocell.They performed 2 maximal sprints for each sprint distance on standing start with 2-3 min recovery following 15 min warmup including self-paced running, calisthenics and flexibility exercises.The better of the two trials for each test was retained for statistical analysis.

Jump Tests
Customized Precision Timing System (PTS) (Tümer Electronic Ltd, Turkey) was used to measure the time data needed to calculate the jump height and power in a vertical jump.The system included 2-channel of data acquisition, an electronic receiver, and a switching mat.Time data [flight time (FT) for SJ and CMJ] of SJ and CMJ sampled at 1000Hz was recorded using of ESC 2XXX Series Data Acquisition Software of PTS.Formula-1 of Bosco et al. (Bosco, Luhtanen, & Komi,1983) were used to obtain all jump height.
Each player had a 15-min warm-up including self-paced running, calisthenics and flexibility exercises before the tests.When performing SJ, the subjects flexed the knees until they felt a comfortable starting position, semi-squatting position, normally occurred at a knee angle of about 85º (Bosco, & Komi,1979) without a preliminary downward movement.CMJ was performed maximum jump with hands kept on the hips, started from an upright standing position following a preliminary downward movement by flexing the knee approximately to the same knee angle as the starting position in SJ.Elastic power (CMJ-SJ dif ) calculated from the difference between SJ and CMJ.

Anaerobic Power and Capacity Test
Anaerobic power and capacity (AP and AC) were tested with Wingate test (Monark Exercise AB, Sweden), for 30 s, at an "all out" pace.Each player warmed-up for a 5min period (at 60-70 rpm) after the ergometer was calibrated and seated height was adjusted for each player's leg length.The players pedaled up to their maximum rpm level at least 3 times during the 5 min period.A 5-min recovery was followed after the warm-up and the appropriate amount of weight (between 1 kg and 100 gr) was placed on the weight carriage.With all resistance of the flywheel, the players were instructed to begin pedaling until they reached their maximum rpm within 4 s.At this point, immediately the predetermined fixed resistance (75 gr per kg of body weight) was released to the flywheel and remained there till the end of the test (Inbar, Bar-Or, & Skinner, 1996).Players were motivated in all test period.AP was the highest power output in 5s interval of the test.AC was the mean power output in 30 s test.Relative values (W.kg -1 ) of AP and AC were used for statistical analysis.

Aerobic Endurance Tests
Aerobic endurance was determined by an incremental running test on a treadmill (h/p/cosmos/ Gaitway, Germany).Players started running at 8 km.h -1 and took 30 s rest after 3 min running as stated by Midgley et al (Midgley, McNaughton, & Caroll, 2007).Each of the following running load was 3 min followed by 30 s rest and the velocity increases was 1 km.h -1 up to fatigue.Blood samples were taken from ear lops during 30 s rest and were measured with electro enzymatic methods without any process in lactic acid analyzer (YSI 1500, Yellow Springs Instrument, USA).HR was recorded with a device (Polar s810i, Finland).VO 2 for each breath was sampled with a mobile ergo-spirometer (K4b 2 , Italy).HR and VO 2 in last 1min of each running velocity were calculated.The third degree polynomial fit was used to estimate mean RV, HR, VO 2 of induvidual FBLLs on these graphs (Jansen, 2001).It is evaluated as VO 2 max criteria as stated by Smith et al (Smith, McNaughton, & Marshall, 1999).

Laboratory Conditions
Laboratory conditions were measured with an anemometer (0.1±°C, 0.1%±, Traceable, Control Company, USA) before each progressively increasing running test.Laboratory temperature and humidity were 24.0-25.5 o C and 39.9-43.2%.

Statistical Analysis
SPSS 20 software (SPSS Inc., Chicago, IL, USA) was used to analyze the data.Data are presented as mean, standard deviation (mean ± SD).Normality of the distribution with Kolmogorov Smirnov test and homogeneity of variance with Levene test were calculated.Pre-and post-training differences of physiological performance characteristics were analyzed using by Paired samples t-test for the groups.Cohen's d effect size (ES) was used to compare the performance characteristics between ETG and NTG.ES magnitudes were classified according to the scale (≥0.2 = small; 0.2< ES < 0.8 = moderate; ≤0.8 = large) described by Cohen (1998).Probability level for statistical significance was set at p≤0.05.

RESULTS
Pre-and post-training mean ± SD and differences of female handball players in the 6-week pre-season plyometric training for sprints, jumps, anaerobic power-capacity, and aerobic running parameters at FBLLs were given in Table 2.All data were normally distributed and no violation of homogeneity of variance was found.ETG and NTG had no significant differences in the pre-training tests for any variable.Both groups had significant pre-and post-training differences in SS and CMJ (p<0.05).There were small and moderate ES differences in SS (ES = 0.1), CMJ, and CMJ-SJ dif (ES = 0.3, and = 0.3) between ETG and NTG in the pre-training.Moderate and large ES differences in the post-training between ETG and NTG were observed in SJ and CMJ-SJ dif (ES = 0.5 and = 0.3), and CMJ (ES = 0.8).Both groups had significant pre-and post-training differences in AP (p<0.05).The ETG had only significant difference between pre and post-training in AC (p<0.05).AP and AC had large ES differences in the pre-training (ES = 1.0 and = 0.8), and moderate and large ES differences in post-training (ES= 0.8 and = 0.8) between ETG and NTG.There were significant decrease in sprints including 10 m, 20 m, and 30 m (p<0.01)from pre-to post-training in the both groups.Small ES differences in 10 m (ES = 0.1) and moderate ES differences in 20 m and 30 m (ES = 0.5, and = 0.3) were present between ETG and NTG in the pre-training.There were moderate ES differences in 10 m and 30 m (ES = 0.3), and small ES differences in 20 m (ES = 0.1) between ETG and NTG in the post-training.ETG had significant pre-and post-training differences in the all-aerobic running parameters at each FBLL (p between <0.01 and <0.05).ETG had also a significant change from pre-to post-training in VO 2 max (p<0.01).There were no statistically significant changes in any aerobic running parameters at all FBLLs from pre-to post-training in NTG.There were small and moderate pre-and post-training ES differences in aerobic running parameters (0.1≤ ES ≤ 0.6), between ETG and NTG.

DISCUSSION
This study was aimed at examining the effects of the 6-week pre-season plyometric training on performance characteristics in female handball players.
There were significant pre-and post-training differences in ETG and NTG for SJ and CMJ in this study.Both groups increased SJ and CMJ after training.Nagano et al (Nagano, Komura, & Fukashiro, 2007) have stated that maximum strength development with weight training, focusing on muscles around knee joint, and doing combined jumping workouts and teaching how to athlete uses these strengthened muscles improve athletes' jump performance.In the present study, it was shown that handball players were stressed with this type of training in the pre-season.
Gehri et al (Gehri, Ricard, Kleiner, & Kirkendall, 1998) found that jumping ability developed with CMJ training that provided contractile component rather than elastic component due to higher positive energy production.Because the foot heel does not touch the floor immediately after landing on the floor, an athlete should produce an optimum jump performance related to short take off time.Markovic Bosco and Komi (1979) stated that plyometric training was a loading consisting of concentric contractions after eccentric loading and thus they bring about stretch reflex, muscle elasticity, neuromuscular adaptation of the Golgi tendon organ (GTO).Stretch reflex is started at eccentric phase and thus it can help to recruit much more motor unit at concentric phase.Elastic power is stored in serial and parallel components of muscle connective tissue.When the power is transferred rapidly in concentric phase, additional force has occurred.The GTO has a protective function against load including extra tension in the muscle however, Hutton, & Atwater, (1992) have stated that plyometric training caused loss of sensation in the GTO and had a potential for overcoming of more tension for elastic elements of muscle.
Sprint running is an important neuromuscular performance characteristic for success in elite female handball (Wagner et al, 2014;Granados et al, 2007).Relationships among running velocity, strength and muscular power of the knee extensor muscles have been found in elite female handball players, suggesting a possible transfer from the gain in leg muscle 152 power into enhanced sprint performance (Jensen et al, 1998).Sprinting is involved multiple joints and segments that are delicately coordinated during each stance phase and requires different inter-and intra-muscular coordination.Young ).Therefore, it should be stated that a 6-week pre-season plyometric training for sprint running is an effective training method for handball players.The key points that handball players have an acceleration and chance direction in a short distance.
ETH and NTG had significant pre-and post-training differences in AP (p<0.05) but ETH only had a significant difference in AC (p<0.05).No literature has been related to the effects of plyometric training on AP and AC in women handball players, which allows making a comparison.However, the result of present study showed that a 6-week plyometric training in pre-season helps to increase in AC.
There were significantly differences in ETG between pre-and post-training related to aerobic endurance parameters including RV, HR, and VO 2 at all FBLLs in addition to VO 2 max.This differences especially VO 2 explained that the training effects occurred.Jensen et al (1997) found that VO 2 max values of Norwegian women handball players in pre-training had 51.3 ± 2.3 ml.kg.min -1 and post-training 53.8 ± 2.7 ml.kg.min -1 but the present study has showed that VO 2 max values of Turkish women handball players in pre-training was 49.0-49.1 ml.kg.min -1 and in post-training was 50.5-51.5ml.kg.min -1 .Although VO 2 max values in Jensen et al (1997) have been high-er than the present study, there are similar increases in these two studies as training effects.As results of these two studies, it can be claimed that a 6-week plyometric training during pre-season has positive contributions to aerobic capacity of women handball players.The athletes, at a higher VO 2 max level, show higher accomplishment to resynthesize of phosphocreatine after high intensity intermittent workouts (Tomlin, & Wenger, 2001)
training days and 2 rest days on Wednesday and Sunday.Each training day included a 2-hour morning session and a 2-hour evening session.Each session started with 15min warm-up including self-paced running, calisthenics, and flexibility exercises and ended up with 10min cool-down including self-paced running and flexibility exercises.ETG group performed additional plyometric training [4 exercises (hurdle jumps, lateral multi jumps for plantar flexors and leg extensors, and frontal multi jumps) of 3 sets of 12 reps].The rest of 30-40 s was allowed between exercises and 3 min between sets.The exercises were integrated in the first and fourth days on the each training week to allow for sufficient recovery between workouts as recommended by researchers Adams et al (Adams, O'Shea, O'Shea, & Climstein, 1992).
, McDowell, & Scarlett (2001) found a significant increase in 30 m sprint performance after six-week sprint training in experienced team sport athletes.Chelly et al (Chelly, Hermassi, Aouadi, & Shephard, 2014) stated that 8-week in-season plyometric training significantly changed 0-5m and 25-30m sprint velocities.The studies are supported by the present study that there are significant pre-and post-training differences in 10 m, 20 m, and 30 m sprints (p<0.01

Table 1 .
Training components of 6-week pre-season

Table 2 .
Effects of plyometric training on performance characteristics in female handball players Note: Subject characteristics are given as Means±SD.ES = effect size.FBLLs = fixed blood lactate levels.Significant difference from pre-training values, *p<0.05,**p<0.01.
(2007) has stated that plyometric training improved SJ 4.7%.When compared to Markovich (2007)'s study, the present study results have different outcomes.The pre-season training could be the reason for these differences because of individual training effects.Progressive intensive jump or sprint training can develop musculo-tendon complex elasticity and supportive structure of body via ability of energy storage (Elliott, Wagner, & Chiu, 2007).Because of connective tissue adaptation and elasticity increase in this high force development, muscles specialized in sports are trained with exercises improving stretch shortening cycle.Plyometric training is an exercise method that uses stretch shortening cycle and jumping movement.Malisoux et al (Malisoux, Francaux, Nielens, & Theisen, 2006) found 12% increases in muscle strength and 13% in vertical jump height after 8 weeks of training including plyometric jumps that effective for stretch shortening cycle exercise performance.
. Besides this, plyometric training enhances strength and power development.The application of carefully programmed plyometric training can have potentially positive effects of aerobic endurance training varieties in RV, HR, or VO 2 at FBLLs reflecting regeneration, extensive and intensive tempo, extensive and intensive interval.Jumping interval training included in traditional endurance training induces moderate to large effects on neuromuscular and physiological parameters (Ache-Dias, Dellagrana, Teixeira, Dal Pupo, & Moro, 2016) and can be fundamental to enhance female handball players' performance.Training volume and training intensity can also be oriented.CONCLUSIONPre-season training results in significant increases in sprints, squat and countermovement jumps, VO 2 max, RV, HR, and VO 2 at FBLLs in female handball players.Such increases are likely to be considered advantages because these bio-motor characteristics give the athletes forceful muscle contractions as well as necessary endurance for some handball game actions, such as sprinting, throwing, blocking, jumping, pushing and shuttle-run.In conclusion, it was found that a 6-week plyometric training is an important parameter in addition to physical fitness, technical and tactical training for the female handball players who get prepared for the woman handball Super League which affects pre-season performance characteristics.