Effects of Plyometric and Repeated Sprint Training on Physical Performance

The purpose of study was to resolve the e ect of plyometric training and repeated sprint training on physical performance. The study was conducted on 41 subjects in two experimental groups (plyometric/repeated sprints training). Before and after the training program, subjects were subjected to diagnostic procedures that included standard test protocols. Results proved a statistically signi cant di erence only after the plyometric training program compared to the repeated sprint group in countermovement jump (8.65% vs. 2.21%). In variable repeated jumps, an increased value was recorded (2.9% vs. 4.29%), like in sprint variables after the training program where certain trends of progress happened after the repeated sprint ability training and the speci city of the program (5 m=0.89%, 10 m=1.07% and 25 m=1.35%), while plyometric training recorded unchanged values at 5 and 10 m, and a 0.27% improvement at 25 m. Stagnation of the 20-yard test was recorded in both groups. There was no di erence between training programs in any variables of functional capacities, with similar measures recorded in repeated sprint ability. After six weeks of both training types, positive changes can be expected in explosive strength of lower extremities, increases in acceleration area, and maximum speed. Keywords: repeated sprint ability; plyometric training programs; performance; sprint; football training 1. Introduction The dynamics of sports games imply the constant repetition of high-intensity (submaximal) or maximal activities intersected by short periods of low-intensity activities or rest that are repeated continuously throughout the match or encounter [1]. Sprinting represents one of the key categories of movement in team sports [2], and this ability diminishes as a result of fatigue as the match or competition progresses [3]. The ability to resist fatigue and maintain the maximum intensity of activity throughout the match or encounter has proven to be a very important ability for team

match or encounter [1]. Sprinting represents one of the key categories of movement in team sports [2], and this ability diminishes as a result of fatigue as the match or competition progresses [3]. The ability to resist fatigue and maintain the maximum intensity of activity throughout the match or encounter has proven to be a very important ability for team sports athletes. This ability is called repeated sprint ability (RSA). The use of notation analysis and the increasing use of GPS (global positioning system) in team sports games (football, rugby, basketball, hockey) have determined the characteristics of the moving structures that appear in these sports, as well as the occurrence of sprints. Football is an acyclic and intermittent sport, where short-lived high-intensity activities, such as 20 m sprints (sprint is de ned as running above 25 km/h) and high-intensity actions such as counter-attacks, are intertwined with low and medium intensity activities (fast walking and jogging), and rests such as standing. Although the total distance covered by players during the match has not changed signi cantly over the years, the demands for high intensity running and longer sprint distances during the match have changed [4]. Using motion analysis, it has been noted that a relatively large number of sprints are realized during matches in sports games, and that greater distance achieved by sprinting di erentiates the top teams [5]. In addition, statistically signi cant Sports2020,8, 91; doi:10.3390 /sports8070091 /journal/sports

Sports2020,8, 91 2 of 13 decreases in sprint distance were found as well as number of sprints and the percentage of time spent sprinting in the second half compared to the rst half. The greatest declines in sprint distance were found in lower quality teams [6]. In professional football players, there is a signi cant correlation between the average sprint time in the repeated sprint ability test and the distance covered by high intensity running (r= 0.65) and sprint (r= 0.6) [7]. The repeated sprint training program presents repetitions of straight or return sprints on a short section with a recovery time of less than 60 s between repetitions. Repetitive sprint training is a training method that is speci c to the development of this ability [1,8], and the authors consider that this improvement is a result of the speci city of the training process itself [9]. Given the demands that team sports put on athletes, the application of strength training programs, explosion training, and plyometric training are technologies that we often encounter during the athletic preparation period. Plyometric training is a popular form of work on physical conditioning of healthy individuals and has been the subject of much research in the last three decades. The available literature [10] states that plyometrics, alone or in combination with other training modalities, produces numerous positive changes in the space of the nervous and musculoskeletal systems, muscle function, and performance in healthy individuals. In team sports such as basketball, handball, volleyball, netball, or Australian football, players must repeat consecutive explosive activities, such as short sprints (from under 5 m until 25 m) with frequent changes of direction [2,11,12], followed by activities such as maximal jumps. In addition, jumps occur mostly after high intensity/sprinting activities, such as vertical jumps after a quick attack in handball [13]. Other studies support the claim that performance improvement in motor-speci c tasks such as vertical jumping, long jump, maximum running speed, as well as running economy can be expected with the use of plyometric training [14–16]. The main aim of this paper is to determine the impact and

activities, such as vertical jumps after a quick attack in handball [13]. Other studies support the claim that performance improvement in motor-speci c tasks such as vertical jumping, long jump, maximum running speed, as well as running economy can be expected with the use of plyometric training [14–16]. The main aim of this paper is to determine the impact and di erences of plyometric training and repetitive straight-line sprint training on motor abilities, functional abilities, and repeated sprint ability. 2. Materials and Methods 2.1. Ethics Committee Approval This study has been approved by the ethics committee of the Faculty of Kinesiology, University of Zagreb. 2.2. Subjects The subjects were students (41) of the rst year in the Faculty of Kinesiology, University of Zagreb and were divided into two experimental groups. All subjects were active athletes from the amateur to semi-pro level. The rst group of subjects (181.23 6.92 cm, 80.54 8.12 kg) conducted repeated straight-line sprint training, and the second group (175.36 6.19 cm, 77.29 9.50 kg) conducted plyometric training. When engaging in the experimental process, the subjects were asked not to take any special supplements that can increase their performance and not to carry out any additional form of physical exercise, while the basic form of physical exercise during the experiment was a practical class on Faculty. All subjects were informed of the purpose of the research and the possible risks of participating in the study prior to conducting it and con rmed their agreement by signing the voluntary consent to participate in the experiment. 2.3. Variable Samples Repeated straight-line sprint ability (RSA)—6 25 m with a start every 25 s The explosive power—jump type # A countermovement jump—CMJ (cm) # Repeated Jumps—RJ (cm) The explosive strength—sprint type

Sports2020,8, 91 3 of 13 # 5 m—SP5 m # 10 m—SP10 m # 25 m—SP25 m Agility test—MAG20y (s) Best straight-line sprint result—RSAb (s) Average straight-line sprint results—RSAp (s) Percentage of decline in straight-line sprint performance during the test—RSA%Sdec (%) # Calculated using [13], the equation %Sdec =100 – RSAp/RSAb 100 Concentration of lactates after repeated straight-line sprint test after 3 min—RSA_La (mmol/L) A subjective load rating (RSA_RPE) Evaluation of functional abilities—progressive spiroergometric load test on a treadmill # Maximum oxygen uptake—VO 2max # Maximum speed of treadmill—vmax # Maximum speed of treadmill at maximum oxygen uptake—vVO2max # Maximum heart frequency—Fsmax # Peak heart frequency during repeated straight-line sprint test—FSpeak_RSA # Heart rate frequency 1 min after repeated straight-line sprint test—FS1min 2.4. Procedure At the Faculty of Kinesiology, University of Zagreb Diagnostic Center, participants were subjected to measurement of anthropometric characteristics. For de ning the morphological status of the subjects, variables of body height (cm) and body weight (kg) were measured. A set of eight tests was used to test physical abilities, of which seven were chosen to test motor skills, while one was used to assess functional abilities of subjects. Repeated straight-line sprint ability (RSA) was tested as 6 25 m sprint with a start every 25 s. In this test best sprint (RSAb) (s), average of sprints (RSAp) (s), and percentage of decline of sprint performances during the test (RSA%dec) (%) were calculated using the equation RSA%dec=100 – RSAp/RSAb 100. For every subject, concentration of lactates (RSA_La) and subjective load estimation (RSA_RPE) was measured after repeated straight-line sprint test. Explosive strength—sprint type was tested with a 25 m sprint test with time intervals at 5 m, 10 m, and 25 m with 2 min of passive rest between sprints. An average value of 3 sprints was included in the analysis. The explosive power—jump type was tested with the Microgate Optojump Next system to measure the height of the re ection, the duration of contact with the ground, as well as the duration of the ight phase. Countermovement jump—CMJ (cm) was performed in the starting position with the

between sprints. An average value of 3 sprints was included in the analysis. The explosive power—jump type was tested with the Microgate Optojump Next system to measure the height of the re ection, the duration of contact with the ground, as well as the duration of the ight phase. Countermovement jump—CMJ (cm) was performed in the starting position with the subject's hands isolated on the hips and subject's upright standing position for a few seconds. The subject then lowered into a semi-squat to an approximate angle of 90 degrees between the upper leg and lower leg. From the descent, without stopping, the subject performed a maximum vertical jump, and then landed with a slight exion in the knees. The test was repeated three times and the average value of the three results was included in the analysis. In the test of repeated jumps, the subject's hands were isolated on the hips and the subject stood in an upright position outside a measured space. At the sound of a laptop, using system software, the subject jumped into the measurement space and performed 6 consecutive jumps from the feet, without bending at the knee joint when in contact with the surface. As a result, the average value of the height of these jumps was taken.

Sports2020,8, 91 4 of 13 A Witty photocell telemetry system was used to test agility in a 20-yard test, which had two parallel lines 10 yards apart with 1 line placed exactly in the middle. From the position of the high start, the subject started the test on a personal signal, which he repeated three times. The subject moved to the side line by touching the line with his foot (exceeding a distance of 5 yards), then sprinted to the other side line where he had to also touch with his foot (exceeding a distance of 10 yards) and nally sprinted to the starting, center line where time was stopped. The average value of the three results was taken as the result. A spiroergometric progressive load test on a treadmill (HC1200, Technogym, Gambettola, Italy) was used to test functional abilities. The test was conducted in a closed and ventilated laboratory with constant standard microclimatic conditions (19–21 C). The subject breathed with the nose and mouth through a breathing mask (Hans Rudolph, Shawnee, KS, USA), which was connected to a bidirectional turbine with an optocoupler air ow reader. A sample of air (1 mL/s) was pulled out of the turbine through a Na on Permapure capillary tube (removing moisture without in uencing the gas concentration) to fast oxygen (zirconium) and carbon dioxide (infrared) analyzers. Ventilation–metabolic parameters were monitored for each breath-by-breath cycle and displayed numerically and graphically on a monitor during real-time testing. The test protocol started with the subject relaxing on a treadmill, and after one-minute, the subject started to walk at a speed of 3 km/h for 2 min at a constant incline of 1.5%. After every 30 s, speed was increased by 1 km/h until the subject was unable to follow the increases in speed. All tests were performed in the hall of the Faculty of Kinesiology according to standard measurement protocols on a hard surface and with constant microclimate conditions. The study program lasted for a total of nine weeks with initial testing in the rst week and introduction trainings (2 times 60 min) in the second

unable to follow the increases in speed. All tests were performed in the hall of the Faculty of Kinesiology according to standard measurement protocols on a hard surface and with constant microclimate conditions. The study program lasted for a total of nine weeks with initial testing in the rst week and introduction trainings (2 times 60 min) in the second week. The experimental program lasted in total six weeks (from the third week until the eighth week) with 3 training sessions per week lasting 60 min each. Research was nished in the ninth week of the program with nal tests. The experimental group conducting plyometric training (Table) performed unilateral and bilateral jumps in the vertical and horizontal directions. The number of sets ranged from 1 to 3 per training session with 120 jumps in a single practice (385 jumps at the end of the week), up to a maximum of 180 jumps per training session (total of 550 jumps per week). The rest between sets ranged from 30 s to 1 min of passive rest, and between types of jumps there was two minutes of passive rest. The experimental group, which conducted repetitive sprint training (Table), had the number of sprints range from 6 sprints in a set in the rst week up to 10 sprints in the set in the last week, with two to three sets per training. The sprints were conducted on a 20 m section with passive rest of 25 s between repetitions and passive rest of two minutes between sets.

Sports2020,8, 91 5 of 13 Table 1.Plyometric training experimental group's 6 week training program. Week 1 2 3 4 5 6 Training 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 Exercises Number of sets/number of repetitions (rest after set)—rest after exercise 1 0 –2 0 Bilateral: jumps from the feet in vertical movement 3/10 (30”) 3/10 (30”) 2/10 (30”) 2/10 (30”) 2/10 (30”) 2/10 (30”) 2/10 (30”) 2/10 (30”) 2/10 (30”) 1/10 1/10 1/10 1/10 1/10 1/10 semi-squat jumps in vertical movement 3/10 (30”) 2/10 (30”) 2/10 (30”) 2/10 (30”) 2/10 (30”) 2/10 (30”) 2/10 (30”) 2/10 (30”) 1/10 (30”) 2/10 (30”) 2/10 2/10 1/10 1 /10 1/10 1/10 semi-squat jumps in horizontal movement 1/10 (30”) 3/5 (30”) 3/5 (1') 3/5 (1”) 3/5 (1”) 1/5 1/5 (1') 2/5 (1') 2/5 (1') 1/5 1 /5 1 /5 1 /5 1 /5 2/5 (1') 2/5 (1') 2/5 (1') Contacts—Bilateral jumps 60 60 55 55 55 50 45 45 40 40 35 35 25 15 15 20 20 20 Unilateral: jumps from the feet (L/R) in vertical movement 2/5 (45”) 2/5 (45”) 2/5 (45”) 3/5 (45”) 3/5 (45”) 3/5 (45”) 3/5 (45”) 3/5 (45”) 3/5 (45”) 3/5 (45”) 3/10 (45”) 3/10 (45”) 1/10 1/10 1/10 2/15 2/10 2/10 semi-squat jumps in vertical movement (L/R) 2/5 (45”) 2/5 (45”) 2/5 (45”) 3/5 (45”) 2/5 (45”) 2/5 (45”) 2/5 (45”) 2/5 (45”) 2/5 (45”) 3/5 (45”) 2/5 (45”) 2/5 (45”) 2/10 (1”) 2/10 (1”) 2/10 (1”) 1/10 2/10 2/10 semi-squat jumps in horizontal movement (L/R) 1/5 2/5 (45”) 2/5 (45”) 2/5 (45”) 3/5 (45”) 3/5 (45”) 2/5 (45”) 2/5 (45”) 2/5 (45”) 2/5 (45”) 3/5 (1”) 3/5 (1”) 2/5 (1”) 4/5 (1”) 4/5 (1”) 2/10 (1”) 2/10 (1”) 2/10 (1”) leg to leg jumps 2 /5 2 /5 2 /5 2/10 3/10 (45”) 3/10 (45”) 1/10 (45”) 2/10 (45”) 2/10 (45”) 3/10 (45”) 2/10 (45”) 2/10 (45”) 2/10 (45”) 2/10 (1') 2/10 (1') 3/10 (1') 3/10 (1') 4/10 (1') Contacts—Unilateral jumps 60 70 80 100 110 110 80 90 90 140 150 150 100 120

(1”) 2/10 (1”) 2/10 (1”) leg to leg jumps 2 /5 2 /5 2 /5 2/10 3/10 (45”) 3/10 (45”) 1/10 (45”) 2/10 (45”) 2/10 (45”) 3/10 (45”) 2/10 (45”) 2/10 (45”) 2/10 (45”) 2/10 (1') 2/10 (1') 3/10 (1') 3/10 (1') 4/10 (1') Contacts—Unilateral jumps 60 70 80 100 110 110 80 90 90 140 150 150 100 120 120 130 150 160 Week 1 2 3 4 5 6 Training 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 Total number of surface contact 120 130 135 155 165 160 125 135 130 180 185 185 125 135 135 150 170 180

Sports2020,8, 91 6 of 13 Table 2.Repeated sprint ability training experimental group's 6 week training program. 1. Week 2. Week 3. Week 4. Week 5. Week 6. Week 1. Training 2 6 20 m 12 sprints 3 6 20 m 18 sprints 2 8 20 m 16 sprints 3 8 20 m 24 sprints 2 10 20 m 20 sprints 3 10 20 m 30 sprints 2. Training 2 6 20 m 12 sprints 3 6 20 m 18 sprints 2 8 20 m 16 sprints 3 8 20 m 24 sprints 2 10 20 m 20 sprints 3 10 20 m 30 sprints 3. Training 2 6 20 m 12 sprints 3 6 20 m 18 sprints 2 8 20 m 16 sprints 3 8 20 m 24 sprints 2 10 20 m 20 sprints 3 10 20 m 30 sprints 36 sprints 240 m Total=720 m 54 sprints 360 m Total=1080 m 48 sprints 320 m Total=960 m 72 sprints 480m Total=1440 m 60 sprints 400 m Total=1200 m 90 sprints 600 m Total=1800 m Total=360 sprints, 7200 m 2.5. Data Analysis Statistical processing software Statistica for Windows version 13.4 (StatSoft, Inc., Tulsa, OK, USA) was used for data processing. The arithmetic mean and standard deviation were calculated for all measured parameters, while the normality of the distributions was tested by the Kolmogorov Smirnov test. E ect size was calculated through partial eta squared. Variance analysis for repeated measures (2 2 ANOVA) was used to analyze di erences between groups after 78 training programs. Additionally, the main e ects and interactions among experimental groups were measured. The statistical signi cance level of the di erences was tested at the 0.05 level. 3. Results 3.1. E ects of Plyometric Training and Repeated Sprint Training on Motor Skills and Repeated Sprint Ability Univariate analysis (Table) of the initial state showed that there were no statistically signi cant di erences between the groups in the initial measurement in the space of explosive strength—jump type. Plyometric training and repeated straight-line sprint training programs resulted in a signi cant improvement in the results

Training and Repeated Sprint Training on Motor Skills and Repeated Sprint Ability Univariate analysis (Table) of the initial state showed that there were no statistically signi cant di erences between the groups in the initial measurement in the space of explosive strength—jump type. Plyometric training and repeated straight-line sprint training programs resulted in a signi cant improvement in the results of countermovement jump, and there were di erences between the groups after the training process. Analyzing the magnitude of the e ect of treatments (plyometric training and repeated sprints) on physical tness through partial eta square obtained through univariate analysis of results, large e ects in the explosive strength of the lower extremities were obtained (0.25). Mean training e ects were obtained in the RSAb and RSA_RPE variables within groups between the nal and initial measurements, but no di erences were obtained in the magnitude of treatment e ects between groups. 3.2. E ects of Plyometric Training and Repeated Sprint Training on Functional Abilities After repeated straight-line sprinting and plyometric training, using univariate analysis of variance (Table) for repeated measurements, there were no statistically signi cant di erences between the experimental groups in the measured variables (VO2max-p=0.737, vmax-p=0.06, vVO2max-p=0.749, FSmax-p=0.141, FSpeak_RSA-p=0.128). Certain di erences in aerobic capacity were obtained in both experimental groups, and there was a positive trend in the repeated sprints program experimental group, but no statistically signi cant di erences were obtained between the groups after the training procedure. Experimental training programs led to statistically signi cant changes in the nal measurements according to initial measurements of the following variables: the maximum speed on the treadmill of 3.6% in the group that performed repeated sprints training versus the 1% of plyometric group (p=0.002); maximum heart rate progress achieved in the progressive load test (p=0.019) by repeated sprint ability group was 1.75%, while other training group had 0.42%); the peak heart rate during the repeated sprint test (p=0.000005) with an improvement of 5.16% compared to the plyometric group (2.66%); and heart rate frequency one minute after repeated straight-line sprint test (p=0.0006) with 6.71% in the repeated sprint ability

This study compares the effects of two training methods on physical performance in athletes.