Effects of Mental Visualization on Plyometric Performance and Self-Confidence of Football Players

Introduction

Football (soccer) is a team sport characterized by intermittent efforts with brief periods of recovery (Mohr et al., 2005). Moreover, during active phases, aerobic and anaerobic phases are successively combined (Rampinini et al., 2007). Accordingly, this sport demands significant physical preparation, which determines the efficiency of these efforts. In this context, cardiorespiratory capacity is an essential quality for optimal performance during competition (Doncaster et al., 2018). However, it has been emphasized that greater precision and performance in gameplay actions can be achieved by developing other physical qualities, such as speed or strength, both of which have been highly specialized in recent years and are crucial elements in training processes (Rodríguez-Rosell et al., 2017).

Specifically, multidirectional speed is a crucial variable in preparing football players, and it is defined as the ability to perform diverse actions such as accelerating, decelerating, or maintaining speed in different directions and during various motor gestures (McBurnie & Dos Santos, 2022). In an open and dynamic sport like football, the succession of pace changes, movements over varying distances, partnerships with teammates, and actions against the opposing team are fundamental skills that must be executed effectively and in the shortest time possible to increase the chances of success (Cossio Bolaños, 2021).

To effectively increase speed in motor movements, there must also be increased strength (Karsten et al., 2016). Indeed, speed is considered a physical capacity that depends largely on the force applied in a motor action (Noguchi et al., 2012). Thus, in speed training, in addition to addressing more specific aspects of motor movements, such as balance or coordination, developing strength is fundamental (Rodríguez-Rosell et al., 2017). Specifically, explosive strength is related to multidirectional speed in movement execution (Di Giminiani & Visca, 2017), and explosive strength can generate benefits in the jumps, turns, and sprints of football players (Cossio Bolaños et al., 2021). Maden-Wilkinson et al. (2021) define explosive strength as the relationship between the greatest force that can be produced in the least time required to generate it.

Thus, when referring to explosive strength, we mean the intensity of a motor action, as it manifests in short actions requiring the application of high force (Bangsbo et al., 2006). Additionally, strength training in football should not be conducted in isolation but should consider the acyclic nature of this sport, reflected in the significant movement variability that can occur during its practice (Elghoul et al., 2022). This makes continuous changes of direction in movement, as well as various jumps and pace changes, a key aspect to train (Gabbett, 2006; Gil et al., 2007). Thus, it is important to work on explosive strength at movements that are as closely related to gameplay movements and intensities as possible.

Explosive strength training in football has been of interest to many researchers (e.g., Hoff & Helgerud, 2004; Marín-Pagán et al., 2020). To achieve this goal, different procedures and strategies can be employed (Hasan, 2023; Liao et al., 2021), among which are plyometrics (e.g., Bedoya et al., 2015). Plyometrics involve training in explosive and short-duration movements, typically including jumping tasks or dynamic movements (Thomas et al., 2009). Plyometrics essentially focus on explosive muscle contractions to improve the muscles’ responses to a maximum intensity requirement (Wang & Zhang, 2016). In its application to football training, plyometrics have shown reliable results in studies by various previous investigators, with improvements of up to 31% in the strength and muscle power of participants (Markovic & Mikulic, 2010), and with broader impact in terms of greater efficiency in jumping actions, acceleration, or reducing displacement times (Thomas et al., 2009).

Separately, various psychological techniques have been implemented to improve athletes’ physical and technical-tactical preparations. For example, visualization has been widely used in sports psychology (Fekih et al., 2021; Lindsay et al., 2022; Suica et al., 2022), and it has been successfully applied in learning new motor skills or perfecting various technical gestures (El-Saleh, 2023; Kim et al., 2017). Applying visualization techniques has provided benefits for motor learning in young adults (Heena et al., 2021) and for improving sports performance (Simonsmeier et al., 2021). Visualization allows the athlete to focus on the task to be trained and to mentally rehearse it, repeatedly performing the action and carefully reviewing each step it comprises (Baeck et al., 2012; Rozand et al., 2014). By repeating mental imagery, athletes reinforce their field training (Rascado et al., 2014).

In sports, the use of visualization has provided benefits in various types and disciplines, including in female badminton players (Hidayat et al., 2023) for whom visualization after breathing and relaxation phases enhanced mental control and improved both psychological and motor skills. Guillot et al. (2013) used visualization to increase tennis players’ serving efficiency, observing that visualisation exercises with an external focus helped to develop technical skills and improve competitive performance. This suggests that visualisation practice consolidates learning and facilitates an automatization of movements. Scott and Scott (2013) achieved performance level improvements in high-level table tennis players with visualization, further emphasizing their value for better motor movement through acquiring the ability to obtain increasingly clearer and more effective mental representations of movements in mental imagery.

Similarly, Bouhika et al. (2016) increased the effectiveness of the number of baskets made by amateur basketball players after using visualization. These investigators observed that visualization could be combined with complementary training factors, such as diet changes, to enhance sports learning processes. Collectively, a proper diet and the use of these mental techniques accelerated athletes’ improvement. In football, visualization training was positively related to athletes’ speed in making direction changes (Sariati et al., 2021), highlighting that the effectiveness of visualization is conditioned by the nature of the task to be trained such that visualization was less effective when used with athletes who were not developmentally prepared, such as when very young athletes with undeveloped muscular systems fared more poorly with visualization methods. Therefore, it is necessary to consider the athletes’ physical capacities when including this type of mental training in their training protocols. Additionally, Robin et al. (2020), investigated the improvement of passing performance with visualization, combining imagery techniques with direct observation to improve motor learning feedback; this approach offered athletes more comprehensive and precise feedback to correct errors and progress further in their acquisition of technical and motor skills.

Applying this type of technique should provide athletes with better resources to face competition demands and thereby increase their competitive self-confidence (Thomas et al., 2021; Yalcin & Ramazanoglu, 2020). Improving an athlete’s belief in their ability to use their own resources to achieve optimal performance (da Silva Silva et al., 2022) has been related to the development and improvement of new skills (Chun et al., 2023). Consequently, if visualization contributes to a football player’s development of technical and motor skills, it should impact their gameplaying confidence.

As observed by previous investigators, combining mental training with other physical training techniques should be based on the players’ developmental readiness to acquire the new motor skills (Robin et al., 2020; Sariati et al., 2021). To do otherwise is to risk training failure. Furthermore, visualization methods in sport require procedures that allow learning to be individualized in a non-linear way (Lindsay et al., 2023). Thus, athletes need dynamic approaches to motor learning that facilitate an adaptation to the athlete’s personal knowledge and skills. When athletes use cognitive control of their movements to improve their technical skills, they also rely on external references (i.e., observed models) for the proper execution of those skills. Since keeping this model in mind helps the novice adapt motor skill execution to the desired standard, trainers should use training models that offer this needed information to athletes about their proper mental execution (Gmamdya et al., 2023).

Combining plyometric techniques with mental imagery has not been previously tested in young footballers. Hence, we expected the results of this research to contribute to an enhanced understanding of a new training method in this context. Thus, our aim in the present study was to analyze the effectiveness of a combined program of plyometrics and mental visualization on speed and explosive strength, and on self-perceived competitive self-confidence in young football players. Likewise, we conditioned this mental imagery procedure with a prior presentation of correct execution models and plyometric executions to promote the learning process.

Method

Procedure

The training program took place at the club’s facilities during regular training hours. Speed, strength, and self-confidence tests were conducted at the beginning and end of the intervention. The program lasted eight weeks, with two sessions per week, aligning with prior recommendations on plyometric training in football (Ramirez-Campillo et al., 2022). The experimental group engaged in a combined program of plyometrics and visualization, while the control group only participated in plyometrics.

Visualization tasks, followed guidelines form Buceta (2020) and included preparatory tasks to develop correct visualization technique. Targeted visualization tasks were carried out 15–20 minutes before plyometric work in all sessions. Visualization tasks occurred in a distraction-free zone, using diaphragmatic breathing to induce optimal concentration. Once this concentration level was achieved, as expressed by the athletes, players were shown videos of each plyometric exercise they were about to perform and asked to mentally execute the same technical action. Players visualized the movement (8–10 minutes), focusing on the entire motor pattern, paying attention to key execution aspects, and mentally repeating forward, backward, and at different speeds.

After completing visualization tasks, players underwent a physical warm-up leading to the actual execution of planned plyometric exercises. Given that feedback enhances task performance (Di Bella et al., 2023) and aids motivation during learning (Souissi et al., 2023), players were provided feedback on their plyometric training in the second, fourth, and sixth weeks to serve as a reference for adjusting their executions based on the previously presented model.

The plyometric tasks consisted of six exercises characterized by their resemblance to movements football players typically make in competition. Collectively, these exercises aimed to develop reactive and powerful accelerations (Jovanovic et al., 2011), as well as improve stability and balance (León Morillas et al., 2021; Paillard, 2019), which are crucial in football. Criteria for exercise selection included their similarity to real actions, based on reactive lower limb movements such as changes of direction, pace, turns, or jumps (McNeil et al., 2021; Sariati et al., 2021). The selected exercises were as follows:

(a) Unipodal Double Anterior and Posterior Skipping: Elevate one leg twice in anterior skipping and subsequently in posterior skipping, alternating legs.

(b) Hurdle Jumps: (1) a slow double jump. Perform a rebound after each hurdle jump to absorb the impact load and perform another hurdle jump; (2) a quick double jump. Perform a reactive rebound after each hurdle jump, minimizing contact time before the next jump; and (3) a double jump without rebound: Perform constant jumps with a single support between hurdles.

(c) Repetitive Long Jumps: Keeping legs together and using arm momentum, jump horizontally as far as possible, absorb the landing, and generate momentum for a new long jump.

(d) Squat Jump: Execute in a static position, with hands on the waist (without impulse) a squat jump by performing a maximum vertical jump by flexing the knees to leverage inertia in take-off.

(e) Depth Jump with Jump to Hurdle: Stand on a platform, drop (without jumping) to the ground, reactively absorb the fall to jump over a small hurdle, and sprint five m after the second support.

(f) Double Unipodal Lunge with Leg Change: Perform a lunge, absorb the jump with another lunge on the same leg, and proceed to perform the same dynamic with the opposite leg, applying unipodal jumps two by two.

These six exercises were divided into two groups of three, based on the jumping or speed mechanics of the exercises. (Kabacinski et al., 2022). Exercises were classified according to the following table (Table 1):

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Table 1.

Classification of Plyometric Exercises According to Their Purpose.

Exercise	Purpose
	Speed	Jump
Skipping unipodal double anterior and posterior	X
Hurdle jumps with slow/fast double jump and without rebound		X
Repetitive long jumps		X
Squat jump		X
Depth jump	X
Double unipodal lunge with leg change		X

Based on the load that the exercises required, exercises were strictly assigned to a specific training day of the week. (For example (a) First day of the week: Hurdle jumps, Depth jump, Double unipodal lunge with leg change; and (b) Second day of the week: Skipping unipodal double anterior and posterior, Repetitive long jumps, Squat jump.) Considering the distribution of each training session in the program, the implementation of exercises was simultaneous. The entire group of football players was divided into three subgroups of five to seven players, and they worked on a specific exercise for the same number of minutes. The group then rotated to the next exercise.

To ensure the principle of progressive overload with the intention of preventing injuries in poorly conditioned athletes (Asadi et al., 2017) and properly adjusting intensities, we used the duration of exercises to modify the workload. Thus, the workload was increased by one minute of training every four sessions. For each of the proposed exercises, the approximate number of repetitions were: Skipping unipodal double anterior and posterior (between 30–40 repetitions), hurdle jumps with slow/fast double jump and without rebound (slow double jump between 15–20 repetitions, fast double jump between 20–25 repetitions, without rebound between 15–20 repetitions), repetitive long jumps (between 20–25 repetitions), squat jump (between 25–30 repetitions), depth jump (between 10–15 repetitions), and double unipodal lunge with leg change (between 20–25 repetitions). Therefore, the workout times were divided into two-week groups (Table 2):

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Table 2.

Duration of Plyometric Training by Week.

Week	Training Time
Weeks 1–2	8 minutes: 6 min. of training (2 + 2 + 2) and 2 min. of rest (1 + 1)
Weeks 3–4	10 minutes: 8 min. of training (3 + 3 + 3) and 2 min. of rest (1 + 1)
Weeks 5–6	14 minutes: 11 min. of training (4 + 4 + 4) and 3 min. of rest (1′5 + 1′5)
Weeks 7–8	18 minutes: 15 min. of training (5 + 5 + 5) and 3 min. of rest (1′5 + 1′5)

Results

Table 3 presents the descriptive statistics for the study variables by participant group. As observed, skewness values ranged from −0.61 to 0.63, and kurtosis values ranged from −1.26 to 2.52. Additionally, as the Shapiro-Wilk test was not significant in any case, we assumed we had normal data distribution and conducted parametric tests.

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Table 3.

Descriptive and Normality Analysis for Study Variables by Group.

		M	SD	S	K	S-W
CG	Self-confidence pre	5.96	.58	−.49	−.32	.94
	Self-confidence post	6.22	.46	−.26	−.78	.95
	Vertical jump pre	47.66	4.65	−.10	−1.25	.94
	Vertical jump post	48.88	4.33	.07	−1.26	.95
	Horizontal jump pre	225.94	14.90	.35	−.48	.96
	Horizontal jump post	229.27	13.87	.63	−.07	.95
	Speed 10 × 5 m pre	15.49	.29	−.61	−.44	.93
	Speed 10 × 5 m post	15.43	.31	.00	−.65	.97
	Speed 50 m pre	7.47	.31	−.37	−.46	.95
	Speed 50 m post	7.42	.32	−.30	−1.07	.93
EG	Self-confidence pre	5.12	.94	−1.14	2.52	.92
	Self-confidence post	5.82	.93	−.47	−.67	.92
	Vertical jump pre	47.15	5.99	−.34	−.48	.96
	Vertical jump post	49.36	5.65	−.51	−.16	.96
	Horizontal jump pre	226.26	19.42	−1.00	.97	.91
	Horizontal jump post	231.78	18.05	−1.22	1.19	.88*
	Speed 10 × 5 m pre	15.53	.37	−.09	2.16	.93
	Speed 10 × 5 m post	15.39	.31	−.87	2.58	.90
	Speed 50 m pre	7.35	.38	.61	−.01	.95
	Speed 50 m post	7.25	.36	.742	.22	.94

We performed a two-way ANOVA (Group x Test Time - pre-test and post-test) that revealed significant interaction effects for the variables of self-confidence (F = 6.33; p = .017; η2 = .15; 1-β = .68), vertical jump (F = 4.25; p = .047; η2 = .10; 1-β = .51), and 50m sprint speed (F = 4.88; p = .034; η2 = .12; 1-β = .57). As can be seen, the effect size was medium and large, respectively, indicating that the independent variable substantially explained the effects produced on the dependent variable. Values close to significance were obtained for the 5 × 10 m speed variable (F = 3.86; p = .057; η2 = .09; 1-β = .48). In contrast, the horizontal jump variable showed no significance (F = 1.50; p = .22; η2 = .04; 1-β = .22). Furthermore, the results indicated that the Levene’s test was non-significant in all cases (p > .05), suggesting equal variance across all variables among the analyzed groups.

Since the interaction effect (group x pre-post) was statistically significant for the variables of self-confidence, vertical jump, and 50-meter sprint test, further post hoc analyses between groups for each assessment and within groups between pre and post-measures were conducted using the Bonferroni statistic. These results indicated a pretest difference in the self-confidence variable, although no statistically significant differences were found in the rest of the variables, either at pretest or at posttest assessments. Additionally, there were differences in the control group between pre and post-test measures in self-confidence (Diff. Pre-Post = −.26, p < .05), vertical jump (Diff. Pre-Post = −1.22, p < .01), and 50-meter sprint test (Diff. Pre-Post = −.05, p < .05). Similarly, there were statistically significant differences in the experimental group between pre and post-test measures in self-confidence (Diff. Pre-Post = −.70, p < .001), vertical jump (Diff. Pre-Post = −2.21, p < .001), and 50-meter sprint test (Diff. Pre-Post = −.10, p < .001).

Discussion

We aimed to analyze the effectiveness of a combined plyometric and visualization program on speed, explosive strength, and competitive self-confidence in young football players. Our results highlighted statistically significant effects of the intervention program on the experimental group on the analyzed physical tests of vertical jump, 50-m speed, and 5 m × 10 m speed, as well as in competition self-confidence. These results demonstrated the positive effects of the combined plyometric and visualization program compared to the program that applied only plyometric training, fulfilling our research objective and confirming our hypotheses.

Firstly, these results emphasized the added effect of visualization in the plyometric program used. This is consistent with previous investigators such as Dello et al. (2021), who found that visualization benefits technical and motor training in athletes. Prior researchers showed that mental training generated cognitive changes that impacted athlete’s motor patterns (Bouhika et al., 2016; Sariati et al., 2021). Specifically, previous investigators showed that visualization training was effective in improving technical skills in athletes (Guillot et al., 2013). We believe that if visualization training had been implemented in these earlier studies, it would have helped athletes improve their execution technique in prior research on plyometric training, making those studies even more effective (Hidayat et al., 2023). Furthermore, various authors highlighted the importance of offering an external focus of attention to promote this type of learning, favoring an individualized adaptation processes (Gmamdya et al., 2023; Lindsay et al., 2023). In this intervention, we used an external focus of attention via video with correct execution patterns that served as a reference for more effective visualization. This too could have increased the quality of this training.

Additionally, our participants’ improvements through these training processes likely contributed to their increasing feelings of mastery and control, which seemed to help them build self-confidence in the tasks performed (Chun et al., 2023; Thomas et al., 2021). Since there was an external reference that offered a reference to the individual evolution of each athlete, the footballers could internally assess the evolution of their own execution skills, and this provided further feedback regarding their plyometric exercise performance. This too likely improved self-perceived self-confidence, affecting their scores on the self-confidence questionnaire completed at pre-testing and post-testing. This is consistent with prior investigators’ notations that visualization processes helped athletes gain self-confidence, positively impacting their sport performance (Vives Ribó & Costa Sánchez, 2022; Montero Herrera, & Carazo Vargas, 2019).

Our control group showed improvement on some of the same variables as the experimental group, but their improvement was smaller. This finding is also consistent with previous positive effects of plyometric training for football activities involving changes of direction, jumps, and changes of pace (Sariati et al., 2021). Since our control group also performed these exercises, it is logical that they would improve physically from pretest to posttest. However, the interaction effects we obtained highlight that adding visualization tasks further enhanced the effectiveness of plyometric training in the experimental group. Thus, this type of combined intervention enhanced the effects of technical and physical training, as postulated by McNeil et al. (2021), Therefore, we concur with Hynes and Turner (2020), and affirmed their finding that athletes who apply visualization to their routine achieve greater success in their sport.

As noted by Markovic and Mikulic (2010), plyometric work was effective in various prior studies with athletes, with 31% improvements achieved in various physical qualities. More specifically, Sariati et al. (2021) showed improvements from plyometric training in the ability to change direction, change pace, and even jump power in football. The process of adaptation and improvement in the execution of plyometric exercises is individualized and is determined by various factors; our data emphasize that one such factor is the use of mental imagery with motor execution models to facilitate the acquisition of these skills and to positively influence learning and executing the motor patterns involved in plyometric exercises.

Conclusion

Our results in this study suggest that combined plyometric and visualization training had a greater benefit to participants than aplyometric-only intervention on footballers’ speed, explosive strength, and competitive self-confidence. This suggests that implementing visualization techniques in technical and motor training programs should contribute to improving training outcomes and attaining a higher level of athletic performance. As further study will be needed, we identified limitations to this study and made recommendations for future investigators.