Effect of Focal Vibration Technique on Lower Limb Performance: A Randomized, Double‐Blind Study

ABSTRACT

The objective of this study was to evaluate the performance capabilities of amateur soccer players using a focal vibration protocol at 120 Hertz combined with stationary bicycle pedaling at 80–90 revolutions per minute for 10 min, in one session per week for three consecutive weeks, to analyze its impact on five countermovement jumps (CMJ). A randomized, double‐blind, parallel‐group clinical trial was conducted at soccer clubs in the province of Tarragona involving a sample of 107 soccer players. The main outcome measures included CMJ height, electrical muscle activation of the vastus medialis of the quadriceps, tibialis anterior, and medial gastrocnemius muscles, and jump, power, velocity, and strength. Repeated measures analysis of variance revealed statistically significant differences in the intervention group: CMJ height (p = 0.04; d = 4.38; power = 0.97), vastus medialis quadriceps (p = 0.001; d = 0.28; power = 0.95), tibialis anterior (p = 0.02; d = 0.24; power = 0.95), internal gastrocnemius (p = 0.005; d = 0.28; power = 0.95), power (p = < 0.001; d = 0.16; power = 0.95), and velocity (p = 0.03; d = 0.39; power = 0.95). These findings demonstrate a statistically significant improvement in CMJ performance following the application of a focal vibration protocol combined with stationary bicycle pedaling at 80–90 revolutions per minute for 10 min, in one session per week for three consecutive weeks, compared to a simulated focal vibration protocol. The results suggest that focal vibration is a valuable tool in the world of football, a high‐impact and high‐power sport.

1. Status of the Topic

Jump performance requires complex coordination between muscular, joint, and neural systems to produce voluntary human movement [1]. Physiological alterations induced by sports practice may lead to changes in muscle function, resulting in decreased lower limb performance. These alterations are often associated with increased soft tissue tension, which can negatively affect muscle strength and power [2, 3, 4, 5, 6, 7, 8, 9].

Numerous prevention and rehabilitation protocols incorporate neuromuscular training methods such as plyometrics, proprioceptive exercises, flexibility training, and strengthening programs [3, 4, 5, 6, 7, 8, 9]. However, despite their effectiveness, these interventions may require prolonged implementation periods to achieve meaningful performance improvements. To address these limitations, focal vibration (FV) has been introduced as a complementary strategy to enhance muscle strength, power, and proprioception, potentially reducing rehabilitation time [10].

The effects of FV are primarily attributed to the stimulation of somatosensory receptors involved in joint position sense and movement control [2, 10]. These afferent signals are processed through the thalamus, facilitating sensorimotor integration and neuromuscular activation [11]. Additionally, FV may enhance jumping performance by enabling the musculature to operate at high frequencies (≥ 100 Hertz (Hz) over sustained periods without compromising physical integrity [12, 13, 14].

The application of FV varies considerably across studies, particularly regarding vibration frequency and muscle state during stimulation. According to Fattorini, L. et al. (2021), the most used vibration frequency in the literature is approximately 100 Hz [1]. In contrast, studies conducted by Casale, R. et al. (2009) [15], Pietrangelo, T. et al. (2009) [16], and Iodice, P.B. et al. (2011) [9] employed higher frequencies close to 300 Hz but reported no significant improvements in muscle strength or power, as assessed by maximum voluntary contraction [1, 7, 15, 16]. Conversely, Filippi, GM. et al. (2009) [12] and Brunetti, O. et al. (2012) [8] applied FV at 100 Hz, with three daily applications of 10 min over 3 consecutive days, and observed significant improvements in muscle power and vertical jump height. FV effectiveness does not depend on a single frequency value but on stimulation within an optimal high‐frequency range. Mechanoreceptors involved in neuromuscular control respond to a spectrum of high‐frequency stimuli, allowing small variations to modulate afferent input without altering the underlying mechanisms. Accordingly, a 120 Hz vibration frequency represents a controlled increase in stimulus intensity within the effective range reported in the literature, potentially enhancing neural activation and reducing sensory habituation when combined with dynamic motor tasks.

Furthermore, Osawa, Y., and Oguma, Y. (2013) investigated the effects of combining FV with a 13‐week exercise program consisting of isometric, concentric, and eccentric lower limb exercises, as well as countermovement jump (CMJ) training. Significant improvements in maximum isometric contraction, concentric strength, and CMJ height were observed exclusively in the group receiving FV combined with training [17]. The authors selected the CMJ over other jump tests due to its strong validity for assessing explosive power and its applicability in both trained and untrained populations [18, 19, 20, 21].

Supporting these findings, Markovic, G. et al. (2004) demonstrated that the CMJ is the most valid and reliable field test for assessing lower limb explosive power, based on comparisons with various vertical and horizontal jump tests and squat assessments [21].

Therefore, the primary aim of this study is to evaluate the performance capacities of amateur soccer players using a 120 Hz FV protocol combined with pedaling on a stationary bicycle at 80–90 revolutions per minute for 10 min, applied once per week for 3 consecutive weeks, and to examine its effects on five consecutive CMJs.

2. Methods

2.1. Study Design

2.1.1. Type of Study

This study is a randomized, double‐blind, placebo‐controlled clinical trial with two intervention groups where participants and evaluators were blinded. The research was conducted from January 2022 to November 2024 (36 months) in different federated football clubs in the province of Tarragona. This study was approved by the Ethics Committee for Drug Research (CEIm Pere Virgili Health Research Institute) on December 23, 2021 (Ref. CEIm 195/2021). The current investigation was conducted in accordance with the Declaration of Helsinki promulgated by the World Medical Association [22]. The protocol for this study was registered with ClinicalTrials.gov (NCT06955689). The Consolidated Standards for Reporting Trials (CONSORT) guidelines were followed throughout the study.

The intervention group received FV treatment, and the placebo group received the procedure without effective vibratory stimulation, as the vibration device did not contact the participant's skin. The inclusion criteria were as follows:

• a.Participation in soccer at least three times per week.
• b.No prior or ongoing medical condition or pathology in the area of interest.

The exclusion criteria included the following:

• a.Having a condition or pathology in the lower limbs.
• b.Receiving any type of treatment on the lower limbs from a healthcare professional or alternative (non‐evidence‐based) therapies.
• c.Presence of any absolute or relative contraindications to surface electromyography, inertial sensor, and/or FV.
• d.Refusal to sign the informed consent form.

A double random assignment sequence was created for each club using the EPIDAT version 4.1 program (Xunta de Galicia) to avoid selection bias. Stratified randomization by sex ensure the similar proportion of female and male soccer players in each group.

The anthropometric variables were sex, age, and lower limb dominance. These are represented in Table 1. Lower limb dominance was assessed using the participants' preferred limb for kicking a ball.

Table 1.

Descriptive characteristics of the sample and main study variables at the baseline evaluation (E0).

	Interventiona n = 47	Placeboa N = 60
Descriptive variables
Sex (m/w), n	33/14	43/17
%	70.21%/29.79%	71.67%/28.33%
Age (years)	25.00 ± 5.74	24.64 ± 5.23
Dominant lower limb (r/l), n	41/6	58/2
%	87.23%/12.77%	96.70%/3.33%
Main study variables
Height of CMJ (cm)	28.09 ± 20.64	28.13 ± 18.70
Vastus medialis quadriceps (µV)	0.55 ± 1.10	0.60 ± 0.92
Tibialis anterior (µV)	0.50 ± 0.83	0.54 ± 0.95
Medial gastrocnemius (µV)	0.49 ± 0.96	0.44 ± 1.43
Power of CMJ (W)	2.30 ± 1.68	2.64 ± 1.97
Speed of CMJ (m/s)	2.31 ± 1.60	2.45 ± 2.00
Strength of CMJ (N)	1349.46 ± 1022.35	1261.86 ± 945.31

Abbreviations: CMJ, countermovement jump; cm, centimeters; L, left; M, Man; m/s, meter/second; N, Newton; R, right; W, woman; W, Watts; µV, microvolts.

^a Values are mean ± standard deviation (95%) except for gender and dominant lower limb (n and %).

2.2. Sample Size Estimation

The GRANMO computer calculator (version 7.12) was used to determine and calculate the sample size for the research study [23]. An α risk of 0.05 and a β risk of less than 0.20 were accepted. In a two‐sided comparison, 54 subjects in both the intervention and placebo groups were required to detect a difference equal to or greater than 1.27 units in mean CMJ height. The common standard deviation was assumed to be 2.09, and a 20% anticipated loss to follow‐up [8].

2.3. Procedure

The primary variable of this study was CMJ height (centimeters). The secondary variables were the muscle activation variables in the vastus medialis of the quadriceps, tibialis anterior, and medial gastrocnemius (microvolts), and finally, the inertial variables of CMJ power (Watts), CMJ velocity (meters/second), and CMJ force (Newtons). During all tests, surface electromyography (sEMG) was recorded in the vastus medialis of the quadriceps, tibialis anterior, and medial gastrocnemius. In addition, the inertial G‐Sensor located on the second sacral vertebra was used to analyze CMJ inertial variables.

The procedure of CMJ follows the Bosco methodology [24]. The soccer players jumped from the position, barefoot, as high as possible, and landed in the initial position. The initial position is with the knees fully extended, feet shoulder‐width apart, and hands placed on the iliac crests.

Each participant performed five CMJs, and the mean value of the five trials was used for analysis (Figure 1).

Figure 1.

(A) CMJ initial position. (B) Inertial sensor application. (C) Surface electromyography application.

2.3.1. Inertial Sensor

An inertial sensor placed on the second sacral vertebra (S2), G‐Sensor 2, was used (EU Directive 93/42/EEC and its amendments, including Directive 2007/47/EEC) (109, 110). Inertial sensors are validated tools for jump assessment, as shown by Truppa, L. et al. (2020 and 2021), who found no statistically significant differences in the accuracy of the inertial sensor compared to a validated optoelectrical measurement system for performing a kinematic analysis of the jump [25, 26].

The data collected by the inertial sensor was processed using G‐Studio software. The protocol chosen for the study is that of the commercial house BTS Bioengineering, included in the G‐Studio program in the jumps section, more specifically, the CMJ repetition protocol [26].

The primary variable, CMJ height, and the tertiary variables, CMJ power, velocity, and strength, were obtained by calculating the average peak value of each variable across the five CMJs.

2.3.2. sEMG

sEMG was used to evaluate the electrical activity in the vastus medialis quadriceps, tibialis anterior, and internal gastrocnemius muscles during the five CMJs. The BTS FREEMG 1000 EMGS system (EU Directive 93/42/EEC and its amendments, including Directive 2007/47/EEC) was used. sEMG records potential differences through electrical signals. These potential differences are generated by the depolarization of muscle membranes. The signal produced by the muscles when they contract voluntarily, and the addition of new motor units, is recorded by the electrodes [27].

Once the sEMG signal is recorded, it is analyzed using the BTS EMG Analyzer software. First, the signal is rectified, followed by the application of a low‐pass Butterworth filter with a cutoff frequency of 400 Hz, which eliminates low‐frequency recordings that damage the signal obtained. Second, a high‐pass Butterworth filter with a cutoff frequency of 20 Hz is applied. This filter eliminates results with very high frequencies, which could be caused by the activation of adjacent muscles. Third, the root mean square (RMS) procedure is performed using a fixed window of 100 ms. The RMS procedure is based on an integral that occurs at the frequency points in the sEMG recording, thus normalizing the obtained signal. Finally, autoscaling is performed to display the results in the same units, microvolts [28].

The secondary variables of muscle electrical activation in the vastus medialis of the quadriceps, tibialis anterior, and medial gastrocnemius were obtained by calculating the RMS peak and averaging the five CMJs for each of the muscles.

The subject's skin was cleaned prior to applying the sEMG electrodes. First, the area of interest for the study was shaved, cleaned with alcohol, and dried. Secondly, surface electrodes, 35 mm × 42 mm sEMG electrodes, were placed on the muscle bellies of interest following the regulations of the surface electromyography for the non‐invasive assessment of muscles (SENIAM) [28, 29]. The electrodes are positioned at less than 20 mm parallel to the muscle fibers and perpendicular to the skin surface [29, 30]. Furthermore, they are placed over the muscle core to be assessed [28, 29, 30, 31].

2.3.3. Intervention

Baseline and final measurements were taken by one researcher, while the intervention was administered by a different researcher who was familiar with the FV tool. The intervention was delivered individually to the facilities of the football clubs in the province of Tarragona that participated in the study.

Participants in both groups received one 10 min VF session per week for 3 consecutive weeks.

The intervention began with an identical warm‐up protocol for all subjects.

The warm‐up lasted 20 min divided as follows: 12 min of warm‐up and 8 min of active rest [32, 33].

To start, the participants performed joint mobility exercises for 4 min, as prescribed by the principal investigator.

This is followed by a continuous pedaling session, between 60 and 70 revolutions per minute, lasting 4 min [32, 33, 34].

Finally, the warm‐up concluded with specific plyometric exercises to activate the muscles involved in the CMJ for 4 min, as prescribed by the principal investigator.

The intervention group received three FV sessions, one session per week for three consecutive weeks using the V‐Plus tool from Wintecare. This tool is classified as Type IIa (Ann. IX‐Rule9‐93/42/EEC and SAA) Class I Type B (EN 60601‐1:2006/A1:2013). The vibration heads of this equipment are positioned on the motor point in the vastus medialis of the quadriceps, tibialis anterior, and internal gastrocnemius by means of a fixation strap designed by the manufacturer to keep the vibration head stable on the muscle. At the same time, the subject pedaling a stationary bicycle for 10 min at a speed between 80 and 90 revolutions per minute. The vibration program was set to a default mode of 10 min of continuous vibration at a frequency of 120 Hz.

The placebo group underwent the same procedure as the intervention group. The vibration program was set to a default mode of 10 min of continuous vibration at a frequency of 120 Hz. The model of Iodice, P. et al. (2019) [35] was used to administer this procedure as a placebo. The FV channels were applied without the vibrating head, positioned identically to the intervention group, but without making contact with the participant's skin. The FV tool was activated so the soccer player only perceived a faint vibrating hum (Figure 2).

Figure 2.

(A) Focal vibration application. (B) Focal vibration in intervention group. (C) Focal vibration in placebo group.

2.3.4. Statistical Analysis

The statistical analysis was conducted using IBM SPSS v28. A loss of six soccer players was recorded.

The quantitative variables of the study were recorded as ordinal qualitative variables. A new variable was created for all dependent variables: “Difference” is the product of subtracting the results obtained in the post‐assessment of the third intervention from the data obtained in the baseline intervention. The Shapiro–Wilk normality test was performed to determine the parametric distribution of the sample, and the Student t‐test for independent samples was used to establish the homogeneity of the research groups before starting the study. The ranges of relationships were analyzed according to whether the variables had a normal or non‐normal distribution using Pearson's bivariate analysis and Spearman's bivariate analysis, respectively. The mean and standard deviation were calculated for each variable, and a hypothesis test was performed using the “difference” variable to determine whether significant differences existed once the research study was completed in both groups. Exclusions after randomization are explained in Figure 2. During follow‐up, there was a 4.5% loss of participation, lower than the 20% estimate based on the sample calculation. The significance level was set at p < 0.05.

3. Results

From January 2022 to November 2024, 113 male and female soccer players were recruited. Of these, one player was excluded for not meeting the inclusion criteria. A total of 112 players were then randomized into the intervention group (49 players) and the placebo group (63 players) (Figure 3). They were evaluated, treated according to allocation, and re‐evaluated according to the study protocol. Finally, a total of 47 players in the intervention group and 60 players in the placebo group were evaluated.

Figure 3.

Consolidated standards of reporting trial (CONSORT) flow diagram.

Intergroup analysis (Table 2) revealed a statically significant improvement in CMJ height (p = 0.04; d = 4.38; power = 0.97; +10.96%). Intragroup analysis confirmed these improvements: the intervention group increased CMJ height by 14.45% (p = < 0.001), whereas the placebo group increased by 8.18% (p = < 0.01). The variables related to muscle activation have obtained significance values in the intergroup analysis (vastus medialis quadriceps (p = 0.001; d = 0.28; power = 0.95, +24.13%), tibialis anterior (p = 0.02; d = 0.24; power = 0.95; +3.85%), internal gastrocnemius (p = 0.005; d = 0.28; power = 0.95; +17.39%)). Intragroup analysis showed that biarticular muscles (vastus medialis quadriceps and medial gastrocnemius) exhibited significant activation increases only in the intervention group (p = < 0.001 for both), whereas the monoarticular tibialis anterior showed no significant changes (p = 0.65). In contrast, the monoarticular muscles have not obtained significant results in the intragroup analysis.

Table 2.

Difference between baseline and third evaluation of study variables (E0–E3).

		Mean ± SDa
		Intervention	Placebo	Lower limit	Upper limit	p‐value between groups b	Effect size	Power
Main study variables	Height of CMJ (cm)	4.06 ± 4.45	2.30 ± 4.32	−8.54	12.08	0.04	4.38	0.97
	p‐value in each groupc	< 0.001	< 0.00	—	—	—	—	—
Muscle activation variables	Vastus medialis quadriceps (µV)	0.25 ± 0.31	0.07 ± 0.25	0.07	0.29	0.001	0.28	0.95
	p‐value in each groupc	< 0.001	0.06	—	—	—	—	—
	Tibialis anterior (µV)	0.08 ± 0.30	−0.02 ± 0.19	−0.55	1.33	0.02	0.24	0.95
	p‐value in each groupc	0.65	0.21	—	—	—	—	—
	Medialis gastrocnemius (µV)	0.17 ± 0.34	0.01 ± 0.22	0.05	0.26	0.005	0.28	0.95
	p‐value in each groupc	< 0.001	0.07	—	—	—	—	—
Inertial variables	Power of CMJ (W)	0.26 ± 0.16	0.06 ± 0.17	−0.14	0.26	< 0.001	0.16	0.95
	p‐value in each groupc	< 0.001	0.27	—	—	—	—	—
	Speed of CMJ (m/s)	0.26 ± 0.31	0.09 ± 0.45	0.01	0.32	0.03	0.39	0.95
	p‐value in each groupc	< 0.001	0.12	—	—	—	—	—
	Strength of CMJ (N)	12.98 ± 238.01	66.55 ± 411.97	−187.46	80.33	0.43	346.67	—
	p‐value in each groupc	0.71	0.22	—	—	—	—	—

Abbreviatures: CMJ, countermovement jump; cm, centimeter; E0, baseline evaluation; E3, third evaluation; m/s, meter/second; N, Newton; W, Watts; µV, microvolts.

^a Values are mean ± standard deviation (95%).

^b Significance of the difference in means between groups, independent samples.

^c Significance of the difference in means for each group, dependent samples.

For inertial variables, intergroup analysis revealed significant increases in CMJ power (+6.43%; p = < 0.001; d = 0.16) and CMJ velocity (+6.70%; p = 0.03; d = 0.39). CMJ strength showed no significant difference (+3.31%; p = 0.43; d = 346.7). In the intragroup analysis CMJ power (intervention group (p = < 0.001); placebo group (p = 0.27)), CMJ velocity (intervention group (p = < 0.001); placebo group (p = 0.12)) and CMJ strength (intervention group (p = < 0.71); placebo group (p = 0.22)) nor in the intragroup analysis.

The changes observed in the sEMG and inertial values can be found in Table 2.

4. Discussion

The primary objective of this study was to evaluate the performance capabilities of amateur soccer players through the application of a 120 Hz VF protocol. The goal was to observe the impact of this intervention on five CMJs.

4.1. Average Jump Height

In response to the first specific objective, there are statistically significant differences in CMJ inertial values when comparing both study groups (p = 0.04). Therefore, it can be stated that the proposed VF intervention significantly improves CMJ inertial values.

According to Canet‐Vintró, M. et al. (2024) [36], a single day of intervention with three specific VF application procedures in amateur athletes statistically significantly improved CMJ height (p < 0.001; η ² = 0.301). The protocol proposed by the author is based on controlled active contractions of the lower limb muscles lasting 10 s with 3 s of rest. The first exercise focuses on the last 30° of knee extension, the second is based on 90° hip flexion, and the third is a 5 s isometric contraction. In the three active contraction protocols, the frequency of application of the VF starts at 100 Hz and progressively increases by 10 Hz throughout the treatment until reaching a maximum of 180 Hz [36].

If the results of this study are compared with the primary variable, CMJ height measured in centimeters, and the results analyzed by Canet‐Vintró et al. (2024), it can be observed that the CMJ height with the same intervention protocol, with active mobility without impact and without modifying the Hz of application of the VF, repeated over three consecutive weeks, obtained a 12.63% improvement in the intervention group at the end of the study protocol, compared to 5.66% improvement in the intervention group in the single‐day intervention study [36].

4.2. Muscle Activation of the Main Muscles in the CMJ

It can be stated that VF improves muscle activation in the vastus medialis of the quadriceps (p = 0.001), tibialis anterior (p = 0.02), and medial gastrocnemius (p = 0.005). These findings suggest that the application of VF enhances neuromuscular activation in muscles that play a key role in CMJ execution.

This result supports the assertion of Freitas, T. T. et al. (2019) [37] and Barrera‐Domínguez, F. J. et al. (2020) [38], who indicate that improvements in muscle fiber recruitment positively influence the performance execution of specific sports gestures [37, 38]. In this context, optimal learning and repetition of the CMJ task may favor more efficient motor unit recruitment, allowing a greater number of muscle fibers to be activated in a shorter period of time, thereby improving movement effectiveness.

In line with these findings, Brunetti, O. et al. (2012) [8], Koeda, T. et al. (2003) [10], and Fattorini, L. et al. (2021) [39] reported that the application of VF directly to the muscle induces modifications in cortical plasticity through the stimulation of muscle spindle afferents, which is reflected in modifications of spinal loop excitability. Furthermore, intermittent and variable vibration stimuli may induce greater muscular adaptations due to differential activation of muscle fibers and habituation of muscle tissue, maximizing neuromuscular activation [8, 10, 37, 39].

Continuing along this line, Mandelbaum, B.R. et al. (2005) [40] and Bahr, R. (2007) [41] suggest that greater effectiveness in muscle fiber recruitment enhances the execution of the analyzed athletic gesture, which may be explained by proprioceptive adaptations. These adaptations are thought to result from stimulation of Ia fibers, leading to excitation of α‐motoneurons and promoting long‐term proprioceptive and neuromotor adaptations [38, 40, 41, 42].

According to Enoka, R.M. et al. (2015) [43], this increase in α‐motoneuron activity may produce sustained changes in the central nervous system, contributing to the reorganization of neuronal circuits. These authors demonstrated that high‐frequency VF interventions (≥ 100 Hz) applied for less than 30 min can persistently modify the activation interaction between the vibrated muscle and its antagonist [43].

However, it is important to consider that other authors, such as Canet‐Vintró, M. et al. (2024) [36], Armada‐Cortés, E. et al. (2022) [44], and Hasegawa, T. et al. (2024) [45], have reported a decrease in electrical muscle activity of the biarticular thigh musculature, particularly the rectus femoris, following interventions involving sprint‐based fatigue protocols. This reduction in EMG activity has been attributed to the greater susceptibility of biarticular muscles to fatigue during sprint tasks when compared to monoarticular muscles [36, 44, 45].

Specifically, Armada‐Cortés, E. et al. (2022) [44] studied professional female soccer players and concluded that muscle fatigue following repeated sprint actions (6 × 40 m with 30 s of rest) can be detected through reductions in CMJ height and metabolic markers such as lactate and ammonia. The authors highlighted that in team ball sports, particularly soccer and rugby, the recovery time following sprint‐induced fatigue is longer than in other ball sports.

Similarly, Hasegawa, T. et al. (2024) [45] evaluated the temporal effects of fatigue after a high‐intensity 400‐meter sprint in university‐level sprinters. Their findings showed a significant reduction in CMJ performance immediately after the sprint, followed by partial recovery over time, with CMJ values remaining 11.5% below baseline after 24 h.

When comparing these findings [36, 44, 45] with the results of the present study, it becomes evident that the behavior of lower‐limb electrical muscle activity differs depending on the presence or absence of fatigue. In the present investigation, sprint performance was not assessed, and particular attention was paid to ensuring the absence of acute muscular fatigue during CMJ execution before and after cycling at a constant pace. Under these controlled conditions, the intergroup analysis revealed greater electrical muscle activity in the vastus medialis quadriceps, tibialis anterior, and medial gastrocnemius.

Therefore, the discrepancies observed between previous sprint‐based fatigue studies and the present findings may be explained by differences in experimental design, fatigue induction, and task specificity. Consequently, future research should aim to evaluate the electrical muscle activity of both biarticular and monoarticular lower‐limb muscles in non‐professional soccer players, combining objective and subjective fatigue assessments. This approach would provide a more comprehensive understanding of CMJ performance following VF protocols and help determine whether compensatory strategies emerge due to altered muscle activation patterns, potentially increasing injury risk or movement dysfunction.

4.3. Jump Power, Velocity, and Strength

Finally, CMJ athletic performance was analyzed using the inertial sensor tool: jump power (p = < 0.001), jump velocity (p = 0.03), and jump force (p = 0.43).

In a study by Rodríguez‐Rodríguez, S. et al. (2025), it can be observed that in a single VF intervention combined with non‐impact active exercise, the intervention group obtained positive significance values in mean power (p < 0.001; η ² = 0.475), maximum velocity (p < 0.010; η ² = 0.091), and velocity mean (p < 0.001; η ² = 0.504) in performing a stipulated squat protocol [46].

When comparing these findings to the present study, amateur athletes who underwent a joint mobility protocol combined with high‐frequency VF (≥ 100 Hz), improved kinetically and kinematically the analyzed values, but with a single intervention, no improvements were observed in the physiological assessment. However, as Fattorini, L. et al. (2023) found in their systematic review and coinciding with the results of this study, when a protocol of two or more consecutive sessions is applied, improvements are observed in the activation of the muscle fibers of the muscles involved in the analyzed sports gesture [39, 46].

On the other hand, Azzollini, V. et al. (2024) promote muscle potentiation through 100 Hz VF at an intensity of 120 millibars of body segments in the tendons of the leg muscles while the athlete, belonging to the VF with action observation group, watches a video of a 20 min gym training session designed to strengthen the quadriceps muscle. The author concluded that high VF (> 100 Hz) with active observation of the sports gesture promotes long‐term muscle potentiation and produces an immediate and sustained change in synaptic response capacity and synaptic pathway reorganization, resulting in increased muscle strength [47].

5. Conclusion

The combination of a VF protocol with a non‐impact exercise activation protocol significantly improves CMJ height, muscle activation in the vastus medialis quadriceps, tibialis anterior, and medial gastrocnemius, as well as inertial CMJ power and velocity values, when compared to a simulated VF protocol in amateur soccer players.

Author Contributions

Gisela Cisa‐Ribas: investigation, methodology, project administration, resource, writing – original draft, writing – review and editing. Sonia Monterde Pérez: investigation, methodology, project administration, resources, supervision, writing – original draft, writing – review and editing.

Conflicts of Interest

The authors declare no conflicts of interest.