Abstract
udy investigated the effects of a 10-week plyometric training program on sprint performance, reactive power, and biomechanical muscle properties in soccer players. Twenty soccer players were randomly assigned to an experimental group (n= 10) or a control group (n= 10). Both groups maintained their regular weekly training, with the experimental group performing additional plyometric sessions twice weekly. Pre- and post-intervention assessments included 5 m and 30 m sprint times, Reactive Strength Index (RSI), and biomechanical properties (tension, stiffness, elasticity) of the rectus femoris (RF) and vastus lateralis (VL). The experimental group demonstrated significant improvements in 5 m (p< 0.01; ES = 1.44) and 30 m (p< 0.01; ES = 1.11) sprint times and RSI (p< 0.05; ES = 0.87). No significant changes were observed in muscle tension, stiffness, or elasticity at the group level. However, correlations indicated that higher baseline elasticity in the VL was linked to greater 5 m sprint improvements, while changes in RF elasticity were negatively associated with 5 m sprint gains. These findings suggest that plyometric training effectively enhances short-distance sprint
0.05; ES = 0.87). No significant changes were observed in muscle tension, stiffness, or elasticity at the group level. However, correlations indicated that higher baseline elasticity in the VL was linked to greater 5 m sprint improvements, while changes in RF elasticity were negatively associated with 5 m sprint gains. These findings suggest that plyometric training effectively enhances short-distance sprint performance and reactive power in soccer players. Although group-level biomechanical properties did not change significantly, individual variability in muscle elasticity may modulate training outcomes, supporting the integration of plyometric exercises into soccer training regimens. Keywords:functional performance; physical activity; myotonometry; drop jump; sprint; stiffness 1. Introduction Plyometric training is a widely used method that utilizes a biomechanical mechanism called the stretch-shortening cycle [1]. In this way, we can develop the ability of the neuromuscular system to generate the maximum force in the shortest time possible [2]. Plyometric exercises are characterized by high speed, short duration, and maximum effort, requiring the activation of motor units associated with fast-twitch type II muscle fibers [3]. A study that used a plyometric exercise protocol consisting of 10 sets of 10 jumps in opposing movements showed that this type of exercise caused preferential damage to type II muscle fibers. These results concluded that plyometric training also causes more significant hypertrophy of type II muscle fibers than type I [4]. It usually involves various jumps, Appl. Sci.2025,15, 1451 https://doi.org/10.3390/app15031451
Appl. Sci.2025,15, 1451 2 of 20 leaps, or ballistic throws with the shortest possible contact phase with the ground/object and the most significant intention of jumping or throwing the object. Such training is a common strategy in various sports disciplines [5]. The impact of plyometric training on skeletal muscle hypertrophy is often described as relatively minor. In a comprehensive review of neuromusculoskeletal adaptations and performance to plyometric training from 2010, Markovic and Mikulic [1] concluded that plyometric exercises can potentially induce muscle hypertrophy and are generally weaker than resistance-induced. Plyometric training can positively affect professional and amateur soccer players [6]. Positive effects have also been observed in the form of increased strength among men and women, provided that it is performed with appropriate progression, respecting the principles of tissue adaptation time and at a sufficiently high intensity [7]. In many sports, the sprint component is crucial in the context of reaching a specific spot on the field faster than the opponent [8], as well as, in the case of soccer, winning the running duel for the ball or reorganizing the formation in defensive play. It has also been shown that sprinting (45%) and jumping (16%) are the two motor actions of a football player that most often lead to goal-scoring situations [9]. Moreover, it has been confirmed that combining plyometrics and body mass, including counter-movement jumps, depth jumps, and squat jumps, increases vertical jump height [7]. This type of training increases neuromuscular coordination by training the nervous system, thereby enabling the muscles’ stretch-shortening cycle [10]. Properly programmed plyo- metric training positively affects sprint values, with athletes improving their times over distances of 20 and 30 m. Moreover, no significant differences were found in intensity and the addition of external resistance; however, regarding the results achieved, the selection of exercises proved significant. Combining several exercises yielded better results than prescribing only one type of plyometric exercise [7,11]. Exercises aimed at reactive strength, such as the drop jump, which involves jumping off a platform and then jumping upwards with maximum intent, also significantly improved RSI values [12]. Increased pennation angle, tendon thickness,
however, regarding the results achieved, the selection of exercises proved significant. Combining several exercises yielded better results than prescribing only one type of plyometric exercise [7,11]. Exercises aimed at reactive strength, such as the drop jump, which involves jumping off a platform and then jumping upwards with maximum intent, also significantly improved RSI values [12]. Increased pennation angle, tendon thickness, and increased stiffness are the changes in parameters observed after applying plyometric training [13]. Adaptive changes during training also concern the biomechanical properties of mus- cles, such as muscle tension (F), dynamic stiffness (S), and elasticity (D). Deficits in these properties can cause weakened athletic performance and be a reason for injuries in ath- letes [14]. In the case of the quadriceps muscles, they are one of the risk factors for developing knee joint disorders [15]. The primary function of tendons is to store and trans- mit the mechanical force of muscle contraction to the bones [16]. High values of dynamic stiffness in tendons due to adaptation to the type of training should allow an individual to withstand greater mechanical loads. The study examined whether significant biomechanical changes occur in the femoris muscles following a training program, using the Myoton device for measurement. Conse- quently, a study enhances the range of measurement techniques available by incorporating this device. There is a need for more evidence regarding the methodology of this training, the types of exercises, and the assessment of changes in the biomechanical properties of muscles and their impact on the athlete’s motor skills. Therefore, this experimental study aimed to assess the impact of a 10-week plyometric training program on running speed, selected parameters of explosive muscle strength, and changes in the biomechanical prop- erties of the quadriceps muscles (muscle tension, flexibility, muscle stiffness) in amateur football players.
Appl. Sci.2025,15, 1451 3 of 20 2. Materials and Methods 2.1. Participants The G* power (v3.1.9.6, Kiel University, Kiel, Germany) software was employed to determine the a priori sample size. Recruiting at least 16 participants was necessary to achieve an effect size level of 0.6 (α= 0.05; power = 0.96) [17]. Twenty male football players (n= 20) from the KS Polonia Łaziska-Górne football club competing in the IV league (age: 23.5±10.5 years, BMI: 23.97±3.96 kg/m 2 , training experience:14.5±5.95 years ), were randomly divided into two groups: the experimental group (eG-n = 10) and the control group (cG-n = 10) according to the following inclusion criteria: age 16–38 years, with a minimum of 5 years of training experience, training at least 3 times a week. The different ages and experiences of the players taking part in the study represented most of the football teams. All players had current medical examinations, allowing them to participate in football competitions. Exclusion from the examination concerned elevated blood pressure occurring before the examination (pressure >140/90 mmHg) in individuals treated after injuries, damage, or unspecified skin and myofascial musculoskeletal system changes. Exclusion could occur at any time during the study at the participant’s request. All participants actively and regularly participated in training sessions and competitions during the study. The study was approved by the ethics committee of the Polish Physiotherapy Association (RESOLUTION No. 3 March 2024 dated 27 March 2024) and conducted by the Helsinki Declaration. 2.2. Study Design The study was designed as a prospective experimental study with a control group (Figure). The experimental group underwent a 10-week plyometric training program. In contrast, the control group did not undergo plyometric training and followed a standard football training program. The group assignment was done through simple 1:1 random- ization with a random sequence using the website ranomizer.org. The group assignment was independent of the treatment time and the research staff. Each participant underwent an introductory intervention, plyometric training, receiving a 10-min briefing seven days before the study. The control group (n= 10) followed the previously planned training by the coach for the duration of the
simple 1:1 random- ization with a random sequence using the website ranomizer.org. The group assignment was independent of the treatment time and the research staff. Each participant underwent an introductory intervention, plyometric training, receiving a 10-min briefing seven days before the study. The control group (n= 10) followed the previously planned training by the coach for the duration of the study (10 weeks), which was typically football training encompassing the physical, technical, and tactical preparation of the football team players (Table). The experimental group (n= 10) incorporated a plyometric training protocol into their planned training, having previously conducted an introductory session with a research assistant who explained the exercises, demonstrated proper movement patterns, and provided feedback on the performed exercises. Each athlete participating in the study warmed up according to their training habits for about 10 min. The athletes performed the plyometric training protocol twice a week before the central part of the training. For 10 weeks with a minimum of 48 h between training sessions, they performed 60 to 72 jumps by the end of the protocol during one session in 2–4 sets. The break between each series was 120 s. Each competitor was equipped with a heart rate watch to ensure that their heart rate returned to readiness values. The intensity with which the athletes performed the exercises was increased; at the beginning of the protocol, the hurdles they jumped over and the box they jumped off were lower, and by the end, they were higher. The exercises included two- footed hurdles in a straight line, multiple jumps, and a drop from a platform with a reactive rebound. The training protocol is presented in Table. The training was conducted on the field and in the indoor hall at the Municipal Stadium in Łaziska Górne, at 3 Sportowa Street. Sprint measurements, reactive strength indicators, and tissue properties were conducted in the exact location in the afternoon from 5:00 PM to 6:00 PM. For each subject, the same
the Municipal Stadium in Łaziska Górne, at 3 Sportowa Street. Sprint measurements, reactive strength indicators, and tissue properties were conducted in the exact location in the afternoon from 5:00 PM to 6:00 PM. For each subject, the same
Appl. Sci.2025,15, 1451 4 of 20 conditions for task execution and measurements were maintained. All participants were tested under the same conditions (5:00 PM to 6:00 PM). The essential characteristics of the research group are presented in Table. All participants underwent the following measurements: sprint time for 10 and 30 s (s), reactive strength index (RSI-[m.s −1 ]), muscle tension (F-[Na Hz]), stiffness (S-[N/m]), and elasticity (D-[NaN]). The measurements were taken during the following periods: (1) before the implementation of the programmed “pre” training; (2) in the 10th week of the programmed “post” training.Appl. Sci. 2025, 15, x FOR PEER REVIEW 5 of 23 Figure 1. Research protocol. Figure 1.Research protocol.
Appl. Sci.2025,15, 1451 5 of 20 Table 1.Standard training program followed by the control and experimental groups. Day of the Week Type of Training Exercise Workload/Intensity Number of Repetitions/ Working Time Number of Series Tuesday Aerobic capacity and power with football elements Running warm-up ≤60% HRmax 15 min 1 Continuous run 70–80% HRmax 16 min 2 Games in small groups, e.g., “rondo” ≤50% HRmax 10 min 1 Patterns of play in offense or defense ≤50–80% HRmax 15 min 1 Small football games on a scaled-down field - 8 min 2 Stretching + mobility ≤50% HRmax 5 min 1 Wednesday Muscle strength and football tactics Running warm-up ≤60% HRmax 15 min 1 Barbell glute bridge 60% 1RMmax ×10 4 “Plank” position - 1 min 4 Dumbell split squat 60% 1RMmax ×10 per side 4 Tactics and shooting≤50–80% Hrmax 15 min 1 Formations movement ≤50–80% HRmax 15 min 1 Stretching + mobility≤50% HRmax 5 min 1 Thursday Glycolytic capacity and power + set pieces Running warm-up ≤60% HRmax 15 min 1 Shuttle run 90–100% Vmax 30 s 6 Set pieces ≤50% HRmax 20 min 1 Stretching + mobility ≤50% HRmax 5 min 1 Friday/Saturday Friendly game/ league game Football game 45–90 min 1 Stretching + mobility≤50% HRmax 5 min 1 HRmax—maximal heart rate. Table 2.Training program implemented by the experimental group. Exercise Number of Jumps Number of Series Rest Time Between Series Intensity Comment Hurdles jump 8 3 120 s Maximum Hurdles set at the height of 30 cm, successively overcome reactively with the shortest possible contact of the feet with the ground Multi-jumps 10 3 120 s Maximum The athlete performs the longest possible multi-jumps from a short run Drop jump 6 3 120 s Maximum Reactive vertical jump after jumping off a box set at a height of 40 cm
Appl. Sci.2025,15, 1451 6 of 20 Table 3.Essential characteristics of study group (n= 20). Variable Mean ±SD Range Age (year) 22.45 ±3.67 16–30 Height (cm) 181 ±4 173–192 Weight (kg) 78.15 ±7.76 64–93 BMI (kg/m 2 ) 23.82±1.81 20.45–26.86 Training experience. (year) 14 ±2.6 10–20 2.3. Measures 2.3.1. Sprint For sprint time measurements according to the “gold standard” [18], fully automatic photoelectric cells (Microgate Witty System, Bolzano, Italy, 2019) were used (Figure). According to various studies, a setup at intervals of 0 m, 5 m, and 30 m on a natural grass football field does not constitute a significant difference in measurements compared to hard surfaces [19,20] (Figure). Each athlete performed two trials at the maximum possible speed, with complete rest between trials. Previously, each athlete warmed up individually for about 10 min, where each ended the warm-up with a few faster sprints as a precaution before the upcoming test. All athletes were trained in the starting procedures, which are strictly standardized—a standing start and push-off from the more muscular trailing leg (Figure). The photoelectric cells measured the sprint time over two segments: the time for 5 m and the time for 30 m expressed in seconds.Appl. Sci. 2025, 15, x FOR PEER REVIEW 7 of 23 Multi-jumps 10 3 120 s Maximum The athlete performs the longest possible multi-jumps from a short run Drop jump 6 3 120 s Maximum Reactive vertical jump after jump- ing off a box set at a height of 40 cm 2.3. Measures 2.3.1. Sprint For sprint time measurements according to the “gold standard” [18], fully automatic photoelectric cells (Microgate Witty System, Bolzano, Italy, 2019) were used (Figure 2). According to various studies, a setup at intervals of 0 m, 5 m, and 30 m on a natural grass football field does not constitute a significant difference in measurements compared to hard surfaces [19,20] (Figure 3). Each athlete performed two trials at the maximum possi- ble speed, with complete rest between trials. Previously, each athlete warmed up individ- ually for about 10 min, where each ended the warm-up with a few faster sprints as
m on a natural grass football field does not constitute a significant difference in measurements compared to hard surfaces [19,20] (Figure 3). Each athlete performed two trials at the maximum possi- ble speed, with complete rest between trials. Previously, each athlete warmed up individ- ually for about 10 min, where each ended the warm-up with a few faster sprints as a pre- caution before the upcoming test. All athletes were trained in the starting procedures, which are strictly standardized—a standing start and push-off from the more muscular trailing leg (Figure 4). The photoelectric cells measured the sprint time over two segments: the time for 5 m and the time for 30 m expressed in seconds. Figure 2. Microgate Witty System photocells are spaced at the measurement site. Figure 2.Microgate Witty System photocells are spaced at the measurement site.
Appl. Sci.2025,15, 1451 7 of 20Appl. Sci. 2025, 15, x FOR PEER REVIEW 8 of 23 Figure 3. Schematic of sprint measurements. Figure 4. Procedure for sprint measurements. 2.3.2. Reactive Strength Index (RSI) Reactive Strength Index (RSI) RSI describes a person’s ability to transition from ec- centric to concentric muscle contraction quickly and aims to assess the athlete’s reactive strength—muscle strength. RSI was determined using the drop-jump method on the Optojump Next System. The drop jump is reliable for assessing RSI and related kinematic parameters (42). The athletes had to jump down from a height of 40 cm and, upon landing, Figure 3.Schematic of sprint measurements.Appl. Sci. 2025, 15, x FOR PEER REVIEW 8 of 23 Figure 3. Schematic of sprint measurements. Figure 4. Procedure for sprint measurements. 2.3.2. Reactive Strength Index (RSI) Reactive Strength Index (RSI) RSI describes a person’s ability to transition from ec- centric to concentric muscle contraction quickly and aims to assess the athlete’s reactive strength—muscle strength. RSI was determined using the drop-jump method on the Optojump Next System. The drop jump is reliable for assessing RSI and related kinematic parameters (42). The athletes had to jump down from a height of 40 cm and, upon landing, Figure 4.Procedure for sprint measurements. 2.3.2. Reactive Strength Index (RSI) Reactive Strength Index (RSI) RSI describes a person’s ability to transition from ec- centric to concentric muscle contraction quickly and aims to assess the athlete’s reactive strength—muscle strength. RSI was determined using the drop-jump method on the Op- tojump Next System. The drop jump is reliable for assessing RSI and related kinematic parameters (42). The athletes had to jump down from a height of 40 cm and, upon land- ing, perform a vertical jump with maximum intent (Figure). The entire procedure was
Description
Plyometric training enhances sprint performance and reactive power in soccer players.