Rec Sports
Effects of neuromuscular versus plyometric training on physical fitness and mental well-being in male pubertal soccer players
Participants
The sample size estimation was computed using G*Power software (version 3.1.6). Based on findings from a related study from, Hammami, et al.18 who examined the effects of NMT on 15-m CoD speed (Cohen’s f = 0.48) in highly-trained male youth soccer players (Tier 3), an a priori power analysis with a type I error of 0.01 and 90% statistical power was computed. The analysis indicated that 20 participants would represent a sufficient sample. For the purpose of this study, we recruited a total of 24 trained male pubertal soccer players from the same team. These players were randomly assigned to either a NMT (n = 13) or a PT group (n = 11) (Table 1). All participants had 4 ± 0.2 years of organized soccer experience and played in various positions, including defenders, midfielders, and forwards, ensuring a comparable skill and positional distribution across groups. All physical tests were conducted on a third-generation synthetic soccer turf at the soccer academy of Takelsa, Nabeul, Tunisia, under standardized conditions.
Following McKay, et al’s .19 classification of athletes’ training and performance calibre, our participants can be categorized as Tier 2 (trained/developmental) athletes, with at least 4 years of systematic soccer training experience. It is important to note that both experimental groups followed the identical regular soccer training program, supervised by the same coaches. The NMT and PT groups specifically incorporated two weekly PT or NMT training sessions (Table 2). To account for individual development, each participant’s biological maturity status was estimated using the maturity offset method, based on the prediction equation of Moore, et al.20.
Before study participation, players and their legal representatives received information on the study procedures and goals, potential risks, and benefits. Informed consent was obtained from both, the legal representatives and the players. This study adhered to the latest version of the Declaration of Helsinki, and the protocol received approval from the Local Ethics Committee of the National Centre of Medicine and Science of Sports of Tunis (CNMSS-LR09SEP01) prior to study commencement. None of the participating players suffered before (6 months) and during the study from psychological, musculoskeletal, neurological, or orthopedic disorders.
Procedures
A week before the study began, all players attended a familiarization session to become accustomed with the fitness tests and PT as well as NMT exercises. Players assigned to NMT and PT received specific instructions on proper exercise techniques. All participants completed the physical fitness and psychological assessments in a fixed order across sessions. Standardized rest periods were provided between tests to minimize fatigue and ensure consistent testing conditions. The same test sequence was used during pre- and post-testing. Test instructors were unaware of group allocation. To minimize potential fatigue effects on cognitive performance, athletes first completed the five-jump test (FJT), followed by the 15-m CoD and the 20-m linear sprint speed tests, with standardized rest intervals between trials. The mental well-being, emotional intelligence, and attention assessments were then conducted after ensuring adequate recovery time.
Before the physical fitness tests started, all participants conducted a standardized 10-min warm-up including balance exercises (forward/backward beam walking and single-leg stances on unstable devices), submaximal running drills (skipping), and landing drills (snap downs and single-leg drop squats). A 5 min rest period separated each test, with a 3-min rest between individual test trials21. For the physical fitness tests (FJT, CoD, linear sprint), the best out of two trials was recorded for statistical analysis. For the cognitive, somatic anxiety, self-confidence, attention and emotional intelligence assessments, only one trial was performed. All attention and emotional intelligence tests were administered individually in quiet, controlled rooms, under the supervision of trained researchers, to ensure standardized conditions and minimize potential distractions.
A passive control group was not included in this study because it is unethical to not allow young athletes to train for a certain period of time22,23. Since authors from previous studies have already shown that NMT is generally effective for fitness enhancement in young pubertal soccer players10,18, our main goal was to directly compare the specific effects of NMT versus PT.
Anthropometrics
Body height was measured using a wall-mounted stadiometer (Florham Park, NJ) and body mass with an electronic scale (Baty International, West Sussex, England). To estimate body composition, we measured the sum of skinfolds using Harpenden’s skinfold calipers. Subsequently, we non-invasively assessed biological maturity using the maturity offset method according to Moore, et al.20, which has demonstrated consistent prediction errors across both adult and adolescent populations. Accordingly, athlete’s chronological age and body height were included in the following regression equation:
Maturity offset = 27.999994 + (0.0036124 × age × height)20.
Physical fitness tests
Proxies of muscle power
The FJT was used as a proxy to estimate muscle power, following the guidelines of Chamari, et al.24. Players started the test in standing position with both feet flat on the ground and performed five alternating left and right leg bounds, aiming to cover the maximum possible horizontal distance. As dependent variable, the horizontal jump distance was tested to the nearest centimeter using a tape measure. This test has previously shown high test–retest reliability, with an ICC of 0.91 for youth soccer players25.
Change-of-direction (CoD) speed
CoD speed was measured using the 15-m CoD test. Athletes began with a 3-m linear sprint before entering a 3-m slalom section marked by three 16-cm high pylons, spaced 1.5 m apart. After navigating the pylons, athletes cleared a 0.5-m hurdle positioned just beyond the final pylon26. As dependent variable, the best time out of two trials was to taken to complete the test. The 15-m CoD test has demonstrated excellent test–retest reliability, with an ICC value of 0.9326.
Linear sprint speed
For the 20-m linear sprint speed test, players sprinted as fast as possible from a starting line. The sprint time was automatically recorded using photocell gates (Brower Timing Systems, Salt Lake City, UT, USA; accuracy of 0.01 s) positioned 0.4 m above the ground. Each player completed two trials and rested for 5 min between trials. The best (shortest) time was used for further analysis. This test has previously demonstrated excellent test–retest reliability in young soccer players (ICC = 0.97)27.
Mental well-being tests
Tests for the assessment of anxiety and self-confidence
Participants’ competitive state anxiety was tested using the Competitive State Anxiety Inventory-2 (CSAI-2). The Arabic translation of the questionnaire, validated with 13 items by Boudhiba, et al.28 was applied. The CSAI-2 is a widely recognized tool for assessing multi-dimensional anxiety in athletes within competitive environments. This inventory evaluates three core components. First, cognitive anxiety which reflects worries and negative thoughts about performance (e.g., “I am concerned about this competition,” “I am concerned about choking under pressure”); second, somatic anxiety that pertains to the physical symptoms of anxiety, such as increased heart rate or muscle tension (e.g., “I feel nervous,” “I feel tense in my stomach”); and third, self-confidence which represents an athlete’s belief in his ability to perform successfully (e.g., “I feel at ease,” “I am confident I can meet the challenge”).
Participants responded to each item on a 4-point Likert scale, indicating “how do you feel right now” from “not at all” to “very much so.” Each of the three subscales (cognitive anxiety, somatic anxiety, and self-confidence) consists of 13 items. The scores for these items were summed to provide an intensity level for each component. This tool offers valuable insights into how these psychological factors interact with physical fitness, providing a robust framework for tailoring interventions to reduce anxiety and boost self-confidence in young athletes. The translated CSAI-2 included 13 items and it has previously demonstrated excellent test–retest reliability in youth athletes with ICC values of 0.94 for cognitive anxiety (CA), 0.87 for somatic anxiety (SA), and 0.79 for self-confidence (SC), respectively29.
Tests for the assessment of emotional intelligence (EI)
Emotional intelligence (EI) was assessed using the Psychometric Emotional Competence (PEC) scale. Participants responded to 50 items on a 5-point Likert scale (1: strongly disagree, 2: disagree, 3: neutral, 4: agree and 5: strongly agree). The PEC measures both intrapersonal emotional competence (understanding one’s own emotions) and interpersonal emotional competence (understanding others’ emotions) as separate constructs. The instrument also provides a global score representing overall emotional competence. The PEC has previously demonstrated excellent reliability with ICC values ranging between 0.90 and 0.98 for all of the studied items30.
Tests for the assessment of attention
The d2 test was used to evaluate participants’ selective attention, concentration, and mental speed, and is widely recognized for its reliability and validity. The test demonstrates excellent reliability, with ICCs ranging from 0.95 to 0.98 across variables27, and strong criterion, construct, and predictive validity28. The test consists of 14 lines, each containing 47 letters, including the target letters “p” and “d” with 1–4 small marks. Participants were instructed to quickly scan each line and cross out every “d” with exactly two marks, while ignoring all other letters and symbols. Each line was completed within 20 s. The dependent variable was the total d2 test score, calculated as the number of correctly identified target letters minus the number of errors, reflecting attention and concentration performance.
Training programs
Both training programs lasted 8 weeks and were integrated into the players’ regular in-season soccer training from February to March 2025. Prior to the intervention, all participants followed a typical in-season routine consisting of five weekly soccer training sessions (Tuesday–Saturday), with Sunday designated for competition and Monday for recovery. None of the players had previously participated in NMT or PT programs, ensuring that both training modalities represented novel exercise stimuli for all participants. Each 90-min session began with a standardized 15-min dynamic warm-up (including dynamic stretching, submaximal running, acceleration and deceleration drills, and jump–landing tasks). On Tuesday and Thursday, 30-min blocks of NMT or PT replaced an equivalent portion of the regular soccer-specific training. After these sessions, players performed 40 min of soccer-specific drills, consisting of 20 min of technical and tactical exercises and 20 min of small-sided games with or without goals. On Wednesday, Friday, and Saturday, players completed 70 min of soccer-specific drills following the warm-up (35 min of technical/tactical work and 35 min of small-sided games). All sessions concluded with a 5-min cool-down (Table 2).
NMT primarily included five exercises designed to improve balance, strength/power, linear sprint and CoD speed as well as agility. Players performed 3 sets of 5–10 repetitions for each exercise, with a rest of 60–120 s between sets and exercises31. To ensure progressive overload, the rate of perceived exertion (RPE) was adjusted every two weeks using a 0–10 OMNI scale. During weeks 1–2, we targeted an RPE score of 3. During weeks 3–4, an RPE score of 5–6 was programmed, and during week 8, the RPE ranged between 7 and 8. All NMT exercises were conducted directly on the soccer pitch (Table 3).
The PT program comprised bilateral and unilateral jump-landing exercises performed in vertical, horizontal, and lateral directions, emphasizing the SSC. The general structure and progression of the plyometric exercises were adapted from Bogdanis et al. (2019), who examined the effects of bilateral and unilateral PT on physical fitness. While the current study drew on that framework for plyometric exercise selection, the overall training design was expanded to specifically target performance components relevant to youth soccer namely, strength, muscle power, sprinting, CoD speed and agility. The intensity, volume, and progression of the exercises were prescribed following established PT guidelines for youth athletes37, ensuring an appropriate load to induce neuromuscular adaptations while minimizing injury risk. Each session included exercises performed in sets and repetitions consistent with prior youth PT interventions, with progression over the 8-week period to maintain adequate training stimuli. More specifically, exercises included drop jumps from a 20-cm drop height, horizontal jumps and lateral hops. Each session involved 3–4 sets of 6–12 repetitions for the three different plyometric exercises (Table 4). Progression was ensured by increasing foot contacts and varying exercise complexity. Participants were instructed to perform all exercises in the SSC at maximal effort and with minimal ground contact time.
Total training volume and intensity (overall time and effort spent training) were similar between PT and NMT. Training was supervised by qualified coaches and experienced sport scientists to ensure safety and effectiveness throughout the study period.
Statistical analyses
Data are presented as group mean values and standard deviations (SD). After data normality was confirmed using the Shapiro–Wilk test, a MANOVA was applied to detect baseline between-group differences. A 2 × 2 analysis of variance (ANOVA) with repeated measures was computed on the factors group (NMT, PT) and time (pre, post) to determine training effects. Post-hoc tests with Bonferroni adjustments were conducted to identify group-specific pre- to post changes. Effect sizes for main time and group effects as well as group-by-time interactions were taken from the ANOVA output (partial eta squared transferred to Cohen’s d). Within-group Cohen’s d effect sizes (ES) were also calculated using the equation: d = (mean post − mean pre-) / mean SD.
The effect size d can be classified as small (0.00 < d < 0.49), moderate (0.50 ≤ d < 0.80), and large (d > 0.80)32. Pearson’s correlation coefficients were computed to assess potential associations between selected measures of physical fitness and mental well-being in pubertal soccer players. Correlation coefficients were considered trivial (r < 0.1), small (0.1 < r < 0.3), moderate (0.3 < r < 0.5), large (0.5 < r < 0.7), very large (0.7 < r < 0.9), nearly perfect (0.9 < r < 1.0), and perfect (r = 1.0)33. The level of significance was established at p < 0.05 and SPSS 20.0 was used for statistical analyses (SPSS Inc., Chicago, IL, USA).