Ht ∗ (0.00744 ∗ CAG2 + 0.00088 ∗ CTG2 + 0.00441 ∗ CCG2)+(2.4 ∗ sex ) − (0.048 ∗ age ) + race + 7.8 (3)

Ht: height (m); CAG: corrected arm girth (cm); CTG: corrected thigh girth (cm); CCG: corrected calf girth (cm); Sex (1 for male and 0 for female); Race (−2 for Asian, 1.1 for African American and 0 for white or Hispanic)

*2.3. Exercise Protocol*

Participants in the EG completed a rise, activate, mobilize, and potentiate (RAMP) system warm-up protocol [48] followed by a 24 min NMT program, three times per week, for 10 weeks. Participants in the CG followed the same warm-up protocol. Then, they completed their normal strength and conditioning program for 24 min (Table 3). Both groups were exercised equally and there was no significant difference between groups. Two weeks before the beginning of the intervention, four familiarization sessions were executed in the EG to get to know the exercises included in the NMT program (Figure 2).

**Table 3.** Training intervention details.


NMT: neuromuscular training; reps: repetitions per set; s: seconds; RPE: rate of perceived exertion (0–10); RT: running technique; SD: standard deviation.

**Figure 2.** Project design timeline. NMT: neuromuscular training; RAMP: rise, activate, mobilize, and potentiate. **Figure 2.** Project design timeline. NMT: neuromuscular training; RAMP: rise, activate, mobilize, and potentiate.

The intensity of the CG and EG training sessions was recorded using the modified Borg scale (0–10 rating), which is valid to control the training intensity and is commonly used by these players in their physical preparation [49,50]. At the end of the physical preparation, the players individually indicated their level of perceived exertion. The average for each of the sessions is shown in Figure 3.

average for each of the sessions is shown in Figure 3.

thirty training sessions. EG: experimental group; CG: control group.

average for each of the sessions is shown in Figure 3.

*Biology* **2022**, *11*, x 7 of 16

**Figure 3.** Average intensity (mean and standard deviation) using the modified Borg scale over the thirty training sessions. EG: experimental group; CG: control group. **Figure 3.** Average intensity (mean and standard deviation) using the modified Borg scale over the thirty training sessions. EG: experimental group; CG: control group. The NMT program (Figure 4) included exercises from six different categories: (1) mobility, (2) dynamic stability, (3) anterior chain strength, (4) lumbopelvic control, (5)

The intensity of the CG and EG training sessions was recorded using the modified Borg scale (0–10 rating), which is valid to control the training intensity and is commonly used by these players in their physical preparation [49,50]. At the end of the physical preparation, the players individually indicated their level of perceived exertion. The

The intensity of the CG and EG training sessions was recorded using the modified Borg scale (0–10 rating), which is valid to control the training intensity and is commonly used by these players in their physical preparation [49,50]. At the end of the physical preparation, the players individually indicated their level of perceived exertion. The

The NMT program (Figure 4) included exercises from six different categories: (1) mobility, (2) dynamic stability, (3) anterior chain strength, (4) lumbopelvic control, (5) posterior chain strength, and (6) COD and was carried out in 4 sets of the 6-exercise circuit (40 s of work and 20 s of gentle running to change to the next exercise). Level 1 exercises were performed during the first 2 weeks, whereas levels 2 and 3 were performed during weeks 3–6 and 7–10, respectively. For unilateral exercises, the working leg changed The NMT program (Figure 4) included exercises from six different categories: (1) mobility, (2) dynamic stability, (3) anterior chain strength, (4) lumbopelvic control, (5) posterior chain strength, and (6) COD and was carried out in 4 sets of the 6-exercise circuit (40 s of work and 20 s of gentle running to change to the next exercise). Level 1 exercises were performed during the first 2 weeks, whereas levels 2 and 3 were performed during weeks 3–6 and 7–10, respectively. For unilateral exercises, the working leg changed between series. posterior chain strength, and (6) COD and was carried out in 4 sets of the 6-exercise circuit (40 s of work and 20 s of gentle running to change to the next exercise). Level 1 exercises were performed during the first 2 weeks, whereas levels 2 and 3 were performed during weeks 3–6 and 7–10, respectively. For unilateral exercises, the working leg changed between series.

**Figure 4. Figure 4.** Neuromuscular training protocol. Neuromuscular training protocol.

#### *2.4. Statistical Analysis*

**Figure 4.** Neuromuscular training protocol. Data analysis of the present study was carried out as both descriptive and inferential. Normality was inspected for all variables using a Shapiro-Wilk test. Macronutrient and energy intake, descriptive data, and possible differences pre-training were analyzed with independent group *t*-student. Within-group comparisons (Student paired *t*-test) were carried out to detect significant differences between the pre-test and post-test in all variables in both groups. A 2 (group) × 2 (time) repeated measures ANOVA with Bonferroni post hoc analysis was calculated for each parameter. Hedges' g effect size with a 95% confidence

interval was also calculated to determine the magnitude of pairwise comparisons for preand post-test and was defined as trivial (<0.2), small (>0.2), moderate (>0.5), and large (>0.8). If the results of the independent sample *t*-test and effect sizes were similar for each group, then the percentage changes were computed and assessed. The significance of statistical analysis was used at the level of *p* < 0.05. All statistical calculations were performed using SPSS (Version 28.0, IBM SPSS Inc., Chicago, IL, USA).

#### **3. Results**

The descriptive characteristics of the players of both groups are shown in Table 1. The results of the analysis showed that there were no significant differences between the two groups in these variables. The average intakes of macronutrients and energy are shown in the Table 2. The results of the analysis showed that there were no significant differences in diet during the intervention in either group.

Table 4 shows the mean and SD of the changes in skinfold variables. At the baseline, there were no differences observed between groups in the above variables, except subscapular skinfold (f = 4.91; *p* = 0.033) and sum of six skinfolds (Σ6S) (f = 4.43; *p* = 0.04).

There were significant main effects of time (*p* ≤ 0.001, f = 24.52, η<sup>p</sup> <sup>2</sup> = 0.39; *<sup>p</sup>* <sup>≤</sup> 0.001, f = 25.46, η<sup>p</sup> <sup>2</sup> = 0.40; *<sup>p</sup>* <sup>≤</sup> 0.001, f = 19.81, <sup>η</sup><sup>p</sup> <sup>2</sup> = 0.34; *p* = 0.009, f = 7.49, η<sup>p</sup> <sup>2</sup> = 0.16; *p* = 0.007, f = 8.00, η<sup>p</sup> <sup>2</sup> = 0.17; *<sup>p</sup>* <sup>≤</sup> 0.001, f = 24.98, <sup>η</sup><sup>p</sup> <sup>2</sup> = 0.39) and a group by time interaction (*p* ≤ 0.001, f = 29.73, η<sup>p</sup> <sup>2</sup> = 0.44; *<sup>p</sup>* <sup>≤</sup> 0.001, f = 47.25, <sup>η</sup><sup>p</sup> <sup>2</sup> = 0.55; *<sup>p</sup>* <sup>≤</sup> 0.001, f = 41.72, ηp <sup>2</sup> = 0.52; *<sup>p</sup>* <sup>≤</sup> 0.001, f = 51.08, <sup>η</sup><sup>p</sup> <sup>2</sup> = 0.57; *<sup>p</sup>* <sup>≤</sup> 0.001, f = 25.22, <sup>η</sup><sup>p</sup> <sup>2</sup> = 0.41; *<sup>p</sup>* <sup>≤</sup> 0.001, f = 68.87, η<sup>p</sup> <sup>2</sup> = 0.64) for front thigh, medial calf, subscapular, iliac crest, abdominal, and Σ6S, respectively. The post hoc analysis indicated that front thigh (EG, *p* ≤ 0.01, *g* = −0.09), medial calf (EG, *p* ≤ 0.001, f = 24.99, η<sup>p</sup> <sup>2</sup> = 0.40), subscapular (EG, *<sup>p</sup>* <sup>≤</sup> 0.01, *<sup>g</sup>* <sup>=</sup> <sup>−</sup>0.12), iliac crest (CG, *p* = 0.02, *g* = 0.02, EG, *p* ≤ 0.01, *g* = −0.04), abdominal (EG, *p* ≤ 0.01, *g* = −0.06) and Σ6S (CG, *p* = 0.019, *g* = 0.01 and EG, *p* ≤ 0.01, *g* = −0.09) skinfolds were significantly reduced. Percent changes of skinfold variables between pre- and post-test are shown in Table 4 and Figure 5.

Table 5 shows the mean and standard deviation in body mass, BMI, fat mass, body skeletal muscle mass, and lean body mass. At the baseline, there were no differences observed between groups in the above variables, except the body skeletal muscle mass Lee (f = 16.71; *p* ≤ 0.001). There were significant (*p* = 0.071, f = 8.17, η<sup>p</sup> <sup>2</sup> = 0.18; *p* = 0.006, f = 8.50, η<sup>p</sup> <sup>2</sup> = 0.18; *<sup>p</sup>* <sup>≤</sup> 0.001, f = 16.39, <sup>η</sup><sup>p</sup> <sup>2</sup> = 0.30; *<sup>p</sup>* <sup>≤</sup> 0.001, f = 32.85, <sup>η</sup><sup>p</sup> <sup>2</sup> = 0.46; *<sup>p</sup>* <sup>≤</sup> 0.001, f = 16.39, η<sup>p</sup> <sup>2</sup> = 0.30) main effects of time and a group by time interaction (*<sup>p</sup>* <sup>≤</sup> 0.001, f = 14.77, ηp <sup>2</sup> = 0.28; *<sup>p</sup>* <sup>≤</sup> 0.001, f = 14.72, <sup>η</sup><sup>p</sup> <sup>2</sup> = 0.28; *<sup>p</sup>* <sup>≤</sup> 0.001, f = 50.19, <sup>η</sup><sup>p</sup> <sup>2</sup> = 0.57; *<sup>p</sup>* <sup>≤</sup> 0.001, f = 50.61, ηp <sup>2</sup> = 0.57; *<sup>p</sup>* <sup>≤</sup> 0.001, f = 50.19, <sup>η</sup><sup>p</sup> <sup>2</sup> = 0.56) for the body mass, BMI, fat mass Withers, body skeletal muscle Lee, and lean body mass, respectively. Post hoc analysis found that the body mass (EG, *p* ≤ 0.001, *g* = −0.04), the BMI (EG, *p* ≤ 0.001, *g* = −0.04), fat mass Withers (CG, *p* = 0.029, *g* = 0.02, EG, *p* ≤ 0.01, *g* = −0.10), the body skeletal muscle mass Lee (EG, *p* ≤ 0.001, *g* = 0.23), and lean body mass (CG, *p* = 0.03, *g* = −0.02, EG, *p* ≤ 0.001, *g* = 0.45) were significantly reduced post-test vs. pre-test. Percent changes of all body composition variables between pre- and post-test, as shown in Table 5 and Figures 6 and 7.

*Biology* **2022**, *11*, 1062


**Table 4.** Summary results of skinfold variables within the control group and neuromuscular training group.

SD: standard deviation; ES: effect size; CI: confidence interval; T: trivial; Σ6S: sum of six skindfolds; \* *p* < 0.05.

**Table 5.** Summary results of other body composition variables within the control group and neuromuscular training group.


SD: standard deviation; BMI: body mass index; ES: effect size; CI: confidence interval; T: trivial; S: small \* *p* < 0.05.

**Figure 5.** Change in skinfold variables assessment for each group and assessment stage. \* Represents a statistically significant difference compared to the pre-test with the superiority of the EG (*p* < 0.05). # Represents a statistically significant difference compared to the pre-test with the superiority of the CG (*p* < 0.05). EG: experimental group; CG: control group. **Figure 5.** Change in skinfold variables assessment for each group and assessment stage. \* Represents a statistically significant difference compared to the pre-test with the superiority of the EG (*p* < 0.05). # Represents a statistically significant difference compared to the pre-test with the superiority of the CG (*p* < 0.05). EG: experimental group; CG: control group. *Biology* **2022**, *11*, x 11 of 16

**Figure 6.** Change in body mass and body mass index variables assessment for each group and assessment stage. \* Represents a statistically significant difference compared to the pre-test with the superiority of the EG (*p* < 0.05). # Represents a statistically significant difference compared to the pre-test with the superiority of the CG (*p* < 0.05). EG: experimental group; CG: control group. **Figure 6.** Change in body mass and body mass index variables assessment for each group and assessment stage. \* Represents a statistically significant difference compared to the pre-test with the superiority of the EG (*p* < 0.05). # Represents a statistically significant difference compared to the pre-test with the superiority of the CG (*p* < 0.05). EG: experimental group; CG: control group.

**Figure 7.** Change in body composition variables assessment for each group and assessment stage. \* Represents a statistically significant difference compared to the pre-test with the superiority of the EG (*p* < 0.05). # Represents a statistically significant difference compared to the pre-test with the

The average intensity registered using the modified Borg's scale (0–10) was recorded over the 30 sessions for both groups (Figure 3). Small magnitudes of differences were

superiority of the CG (*p* < 0.05). EG: experimental group; CG: control group.

found between the average of intensities (*g* = 0.20) between CG and EG.

**Figure 6.** Change in body mass and body mass index variables assessment for each group and assessment stage. \* Represents a statistically significant difference compared to the pre-test with the superiority of the EG (*p* < 0.05). # Represents a statistically significant difference compared to the pre-test with the superiority of the CG (*p* < 0.05). EG: experimental group; CG: control group.

**Figure 7.** Change in body composition variables assessment for each group and assessment stage. \* Represents a statistically significant difference compared to the pre-test with the superiority of the EG (*p* < 0.05). # Represents a statistically significant difference compared to the pre-test with the superiority of the CG (*p* < 0.05). EG: experimental group; CG: control group. **Figure 7.** Change in body composition variables assessment for each group and assessment stage. \* Represents a statistically significant difference compared to the pre-test with the superiority of the EG (*p* < 0.05). # Represents a statistically significant difference compared to the pre-test with the superiority of the CG (*p* < 0.05). EG: experimental group; CG: control group.

The average intensity registered using the modified Borg's scale (0–10) was recorded over the 30 sessions for both groups (Figure 3). Small magnitudes of differences were found between the average of intensities (*g* = 0.20) between CG and EG. The average intensity registered using the modified Borg's scale (0–10) was recorded over the 30 sessions for both groups (Figure 3). Small magnitudes of differences were found between the average of intensities (*g* = 0.20) between CG and EG.

#### **4. Discussion**

The aim of the study was to investigate the effects of a 10-week NMT program on skinfold and body composition variables in highly trained female soccer players. We hypothesized that GE would reduce skinfold values, fat mass, and body mass and increase muscle mass and lean body mass, improving overall body composition.

The main findings of the current work were that 10 weeks of NMT significantly reduced body mass (−0.34%, *g* = −0.04), fat mass (−1.94%, *g* = −0.10), and Σ6S (−1.79%, *g* = −0.09) compared with the CG (0.05%, *g* = 0.01, 0.52%, *g* = 0.02 and 0.4%, *g* = 0.01, respectively). EG and CG were exercised equally, and no significant work intensity was observed between the groups. In addition, body skeletal muscle mass and lean body mass increased in the EG (body skeletal muscle mass: 1.10%, *g* = 0.23; lean body mass: 1.53%, *g* = 0.45) and slightly decreased in the CG (body skeletal muscle mass: −0.10%, *p* = 0.3, lean body mass: −0.10%, *g* = 0.02, respectively).

Previous research in soccer players reported changes in body composition after different resistance training programs [38,40,51–59]. However, no study has been conducted regarding the effects of an NMT program. Of note, the NMT battery applied in the current work includes exercises from six categories: (1) mobility, (2) dynamic stability, (3) anterior chain strength, (4) lumbopelvic control, (5) posterior chain strength, and (6) the ability to COD in this regard, and the effectiveness of each or a combination of these training methods to improve body composition has been considered as a reference for comparing the results of the present study.

Arguably, strength exercises are an effective way to stimulate muscle hypertrophy along with improvements in body composition [60]. Particularly, Falces et al. [55] applied a 16-week strength training program with calisthenics and observed a significant decrease in body mass (ES = −0.08) and fat mass (ES = −0.41) and a significant increase in lean mass (ES = 0.17) in a group of male U17 soccer players. Furthermore, Sánchez-Pérez et al. [54] studied the effects of an 8-week high intensity interval training (i.e., a Tabata workout including calisthenics, plyometrics, and COD ability) in a similar population, showing a reduction in body fat (−1.38%, ES = 0.42) and an increase in lean body mass (1.38%, ES = 0.44), and Suárez-Arrones [40,56] also found differences in the body composition (body fat: ES = −0.99 ± 0.54 and lean body mass percentage: ES = 0.25 ± 0.10) of young male soccer players during a 24-week intervention that included circuit training with some exercises comparable to ours (i.e., posterior chain eccentrics, core stability, and plyometrics). It should be noted that in these last two studies the CG slightly worsened their body composition, just as in the present research.

On the contrary, several studies [58,59,61] assessed training programs that include at least one of the exercise categories applied in the current study in adult soccer players showing no differences in changes in body fat percentage (ES = −0.10) and fat-free mass percentage (ES = 0.09) after 8 weeks or less of intervention. Unfortunately, female soccer players were not included in these works, preventing an accurate comparison with the current data.

Focusing on female soccer players, the study from Polman [52] analyzed the effect of a 12-week physical conditioning program on physical fitness and anthropometric parameters of adult highly trained female soccer players. After the intervention, decreases in body mass (ES = −0.24), BMI (ES = −0.28) and fat mass (ES = −0.16) were found. Although the exercise program in Polman's study is similar to the one included in our study (e.g., balance, jumps, and COD ability), their athletes showed greater improvements than the athletes in the present study. A possible explanation for this little discrepancy could be the longer duration of their intervention and/or the higher body fat percentage of their players at baseline. Remarkably, the mean values for body mass and fat percentage at baseline in the current work fall within the values reported in a review of international female soccer players (56.8–64.9 kg and 14.6–20.1%, respectively) [5], whereas those from the aforementioned study do not.

In contrast, to the best of our knowledge, this is one of the first studies to assess the effects of 12-week plyometric training on body composition, explosive strength, and kicking speed of 20 female soccer players [53]. The results showed an improvement in performance variables but no significant changes in body composition However, changes in muscle strength through plyometric training produce adaptations of the neuromuscular system rather than muscle hypertrophy [62]. Therefore, with unique plyometric training, body composition can be expected to remain unchanged.

Of note, one study [38] analyzed the effects of a 12-week NMT program on the body composition of female volleyball athletes. Though the sports have different metabolic requirements, (football and volleyball), Simões et al. showed an increase in body mass (ES = 0.08) and lean body mass (ES = 0.36) and a reduction in fat mass (ES = −0.50) [38])**.** In the same direction, the study by Sudha and Dharuman, which evaluated the effects of a 12-week circuit training program combined with different neuromuscular activities in schoolgirls, observed a decrease in BMI (ES = −0.49) [51]. This data, although from a different sample, contribute to reinforcing the results obtained in the present research and highlight that the assessment of body composition is closely related to performance and helps to confirm the training effect [62,63].

Some limitations need to be acknowledged for a correct interpretation of the results. Firstly, it should be mentioned that the sample used is small and the data is limited to a certain group of soccer players, so it would be interesting to carry out further studies to confirm the present results. Female soccer players have characteristics that do not allow us to extrapolate our results directly to other sports. This study did not take into account variables related to the genotype of the female athletes and protein intake above the recommended dietary allowance was not controlled. We recommend that future research examines the relationship between different endocrine parameters (i.e., IGFBP-3, erythropoietin, or estrogen for female athletes) and genes related to performance and body composition, such as angiotensin-1 converting enzyme insertion/deletion (ACE I/D) polymorphism or α-actinin-3 (ACTN3) R577X polymorphism. Future studies should

extend these observations to other age groups, competitive levels, and larger samples in order to analyze whether the results are similar. Furthermore, it would be beneficial to observe different intensities and volumes in the NMT program to determine the optimal regimen for this training method as well as observing whether this program can improve body composition in female soccer players.

#### **5. Conclusions**

The present study suggests that the implementation of a 10-week NMT program of just 24 min, three times a week improves body composition in highly trained female soccer players compared to a regular physical preparation training. In this regard, the soccer-specific NMT protocol proposed in this study improved female soccer players´ body composition by reducing fat mass and increasing muscle mass. Therefore, female soccer coaches and physical trainers should be aware that combining strength, mobility, lumbopelvic control, dynamic stability, and change of direction exercises based on soccerspecific requirements may also improve the body composition of their female players.

**Author Contributions:** Conceptualization, A.R.-M., A.C.-L., J.L.A.-S. and D.L.; methodology, A.R.- M., H.N. and A.C.-L.; formal analysis, A.R.-M. and D.L.; investigation, A.R.-M., E.M.-P. and D.L.; data curation, A.R.-M. and D.L.; writing—original draft preparation, A.R.-M., A.C.-L., H.N., E.M.-P. and D.L.; writing—review and editing, D.L., H.N., J.L.A.-S., E.M.-P. and A.C.-L.; supervision, E.M.-P., D.L. and J.L.A.-S.; project administration, A.R.-M. and E.M.-P. All authors have read and agreed to the published version of the manuscript.

**Funding:** This work was supported by Universidad San Jorge (Internal Research Project 2021–2022) and Departamento de Ciencia, Universidad y Sociedad del Conocimiento from the Gobierno de Aragon (Spain) (Research Group ValorA No. S08\_20R).

**Institutional Review Board Statement:** The study was conducted in accordance with the Declaration of Helsinki, and approved by the local Ethics Committee of CEICA (protocol code PI21/011, 10/02/2021).

**Informed Consent Statement:** Informed consent was obtained from all subjects involved in the study. Written informed consent has been obtained from the patients to publish this paper.

**Data Availability Statement:** The data presented in this study are available on reasonable request from the corresponding author. The data are not publicly available due to privacy reasons.

**Acknowledgments:** The authors thank all the subjects who participated in this study.

**Conflicts of Interest:** The authors declare no conflict of interest.

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