Acute Effects of Squat and Ballistic Jump Exercises on Judo-Specific Performance, Handgrip Strength, and Perceived Exertion in Young Male Judokas

Abstract

This study aimed to examine the acute effects of squat and ballistic jump exercises during warm-ups on judo-specific performance in young male judokas. Using a randomized crossover design, 10 sub-junior male judokas (age: 12.9 ± 0.7 years) completed three conditions: a controlled warm-up with only judo-specific exercises and two experimental warm-ups including either a three-repetition maximum (RM) back squat (with ~90% 1RM load) or ballistic jumps (squat jumps, scissor jumps, and double-leg bounds) in addition to judo-specific warm-ups. Following each warm-up condition, participants performed the Special Judo Fitness Test (SJFT), with heart rate measured immediately and one minute post-test. Handgrip strength and ratings of perceived exertion (RPE) were recorded after the SJFT. Both squat and ballistic jump exercises significantly improved judo-specific performance compared to the control condition, with large effect sizes (ESs). The number of throws in set 2 (p = 0.001, η_p² = 0.65, large ES), total throws (p < 0.001, η_p² = 0.70, large ES), and the SJFT index (p < 0.001, η_p²= 0.65, large ES) all showed significant improvements. Regarding the throw in set 2, significant improvements were observed after both squat (p = 0.003, Hedge’s g = 1.78, large ES) and ballistic jump exercises (p = 0.010, Hedge’s g = 1.44, large ES) compared to the control condition. Similarly, total throws were significantly higher in the squat (p = 0.003, Hedge’s g = 1.51, large ES) and ballistic jump (p < 0.001, Hedge’s g = 1.37, large ES) conditions compared to the control condition. Furthermore, the SJFT index showed notable improvements following squat (p = 0.010, Hedge’s g = 0.80, moderate ES) and ballistic jump (p < 0.001, Hedge’s g = 0.90, moderate ES) conditions compared to control conditions. However, squat exercises led to a significant reduction in right-hand grip strength (p < 0.001, η_p² = 0.58, large ES) [p = 0.008, Hedge’s g = 0.19, trivial ES for squat vs. control; p = 0.014, Hedge’s g = 0.23, small ES for squat vs. ballistic jump], with no differences observed in left-hand grip strength or RPE scores (p > 0.05). In conclusion, the integration of squat and ballistic jump exercises into warm-up protocols has been shown to significantly improve judo-specific performance in young male judokas without eliciting an increase in RPE values. However, careful consideration should be given when incorporating squat exercises, as they may lead to localized handgrip fatigue (reduced grip strength due to muscle exhaustion), which could affect performance in grip-dependent techniques.

1. Introduction

Judo is a dynamic martial art that demands athletes execute swift and powerful techniques in matches that can last from a few seconds to 20 min, depending on when a score is achieved [1]. Moreover, success in judo is closely linked to the ability of an athlete to capitalize on brief moments of opportunity with agility, power, and speed [2,3]. Due to the high-intensity nature and demand of the sport, a well-structured warm-up is essential for optimizing performance by enhancing physiological factors such as joint flexibility, metabolic efficiency, and neural activation [4]. A key component of an effective warm-up is the addition of conditioning activities that can induce post-activation performance enhancement (PAPE), a process where preceding high-intensity activity enhances subsequent muscle contractility and force production [5]. The underlying mechanisms of PAPE include increased muscle temperature, intramuscular fluid accumulation (i.e., muscle blood flow and/or water), decreased muscle pH, and increased neural drive (i.e., greater muscle activation) [5].

Various conditioning activities have been studied to induce PAPE across different athletic populations. However, as per the author’s knowledge, only two studies have been conducted on judokas’ judo-specific performance assessed using the special judo fitness test (SJFT) [6,7]. One study [7] reported that contrast-training exercises that included 2 repetition maximum (RM) squats combined with 5 horizontal jumps improved the SJFT index in male judokas. In addition, the authors also included incremental plyometric box jumps (i.e., 20 cm to 40 cm to 60 cm) as another conditioning activity. They reported an increased number of throws in the first set of the SJFT compared to a traditional judo warm-up (i.e., control) [7]. Similarly, another study [6] reported an increased number of throws in the first set of the SJFT after two conditioning activities. The first conditioning activity involved standing long jumps (i.e., lower body exercise). In contrast, the second one involved standing long jumps and resistance band pulls (i.e., a combination of upper and lower body exercises).

Although the previous two studies [6,7] have reported improved SJFT performance after the included conditioning activities (read the previous paragraph), various conditioning activities have been studied in the past two decades to induce the PAPE effects across different athletic populations. For example, McBride, et al. [8] reported improved sprint performance after performing a set of heavy squats compared to control conditions (i.e., warm-up) among football athletes. Another study included a combination of different ballistic jump exercises and reported improved performance among athletes. However, the previous studies that included judo athletes used either a combination of heavy squats with jump exercises [7] or only a single jump exercise (e.g., standing long jumps, plyometric box jumps) [6,7]. Therefore, it would be interesting to see if performing squats alone or a mixture of different ballistic jump exercises can induce a PAPE effect on specific judo-specific performance. It is also worth noting that both the previous PAPE studies on judo athletes were conducted on adult participants, reflecting a necessity for studies on younger participants. Evidence from other sports suggests that junior athletes could benefit from conditioning activity protocols focused on inducing PAPE, but the literature on this topic in junior judo athletes remains scarce [9,10].

Therefore, this study aimed to address this gap by examining the acute effects of squat and ballistic jump as conditioning activities during warm-up protocols to induce PAPE in young male judo athletes (participating in sub-junior competitions) using the SJFT as a performance measure. In addition, the secondary aims of the study were (i) to assess if the conditioning activities have a positive effect on the isometric handgrip strength (an important factor in success in judo); (ii) to assess psycho-physiological exertion measured using the rating of perceived exertion (RPE). Based on previous evidence [6,7], the authors hypothesized that the addition of conditioning activities would induce the PAPE effect and significantly improve the performance measures compared to a control condition (i.e., judo-specific warm-up).

2. Materials and Methods

2.1. Participants

The minimum required sample size for this study was calculated using a priori analysis with G*Power software (version 3.1.9.7). This analysis determined that at least 10 participants would be necessary to achieve statistical significance, considering one group, three measurement points (i.e., squat, plyometric, and control), with an alpha error probability of less than 0.05, non-sphericity correction = 1, correlation between repeated measures of 0.5, a desired power (1-β error probability) of 0.80, and an effect size (Cohen’s f = 0.25), indicating a moderate effect based on within-factors repeated measures ANOVA. A conservative effect size (moderate) was chosen since previous studies on judo athletes were conducted on adult athletes [6,7], and the studies did not provide the required effect size to conduct the a priori analysis.

A total of ten male judokas with seventh and eighth kyu (i.e., belt classification) and having experience in sub-junior-level competitions (i.e., regional level in India) volunteered to participate in the study. The participants were aged 12.9 ± 0.7 years (range 12–14 years) and had a height of 148.9 ± 5.9 cm, a body mass of 43.0 ± 5.9 kg, and a mean body mass index of 19.28 ± 1.15 kg/m². The 1RM squat of the participants was 59.3 ± 17.7 kg with a relative strength level (i.e., participant’s lifting capacity relative to their body mass) of 1.4 ± 0.3 kg/kg. Each participant had at least three years of experience practicing structured judo training and previous exposure to resistance training, specifically being capable of performing squats. Further, to be included in the study, the participants had to be efficient in performing the Ippon Seoi-Nage technique. In addition, no recent injuries were reported by the participants. Before the start of the study, participants were fully informed about the benefits and potential risks of the interventions and provided written ascent. The participants were part of a residential sports academy; hence, their legal guardians signed the informed consent forms. The research was approved by the institutional review board of the School of Physical Education and Sports, Rashtriya Raksha University (approval number: IRB/SPES/2024/04; dated: 9 September 2024) and was conducted in alignment with the ethical standards established by the Helsinki Declaration.

2.2. Experimental Design

The study utilized a randomized crossover design comprising three within-group conditions (i.e., two conditioning activities [i.e., squats and ballistic jump exercises] and a control condition [i.e., judo-specific warm-up]). This design was employed to compare the effects of different experimental conditions on judo-specific performance outcomes. The randomized crossover approach ensured that each participant experienced all conditions while reducing the confounding effects of extraneous variables (e.g., environmental temperature), allowing for a comprehensive comparison of the interventions’ effects on performance [11]. The experiments were conducted at similar times each day (15:00 to 17:00 hours) to reduce the influence of the circadian rhythm and environmental conditions. Additionally, a rest period of at least 48 h was maintained between experimental conditions to prevent any interference from previous interventions [7]. The order of the tests (i.e., SJFT, handgrip, RPE) and the participants performing them remained consistent across all experimental conditions (i.e., control, squat, and ballistic jump conditioning activities).

Furthermore, a one-week familiarization session was conducted before the final data collection. During this time, participants were introduced to and practiced the resistance training exercises (i.e., squats) and various ballistic jumps that would be utilized in the study. The testing procedures were also thoroughly explained and rehearsed, aiming to minimize any potential learning effects that could influence the results. The 1RM assessment for squatting was also conducted during these sessions. In addition, the anthropometric and demographic measurements of the participants were obtained during this familiarization phase. To maintain consistency, participants were advised to adhere to their regular dietary habits throughout the study duration. In addition, the participants were particularly instructed to refrain from consuming large meals within three hours of their scheduled testing sessions to ensure optimal performance and standardized conditions.

2.3. 1RM Squat

Maximal strength testing (i.e., 1RM) has been suggested to be safe for young, healthy athletes [12] and was conducted based on previous recommendations for the 1RM squat assessment [13]. A general warm-up was performed, following which each participant performed sub-maximal lifts that allowed them to complete 8–10 repetitions. Thereafter, based on the previous training experience, the participants were instructed to select a weight that would allow them to perform three repetitions. Using an incremental procedure, the weights were progressively increased, with three to five minutes of rest between each attempt. The testing continued until the participants could not complete one full back squat with proper form.

2.4. Conditioning Activities

The participants were involved in a judo-specific warm-up protocol (i.e., control condition) and two experimental conditions that included additional conditioning activities (i.e., back squats and ballistic jumps). All three protocols started with a 10-minute self-paced jog. The judo-specific warm-up included judo-specific exercises that included 10 repetitions of ukemi drills (i.e., front, back, side, and rolling), 2 sets of 10 repetitions of “rapid” uchikomi drills (i.e., throwing drills), 2 sets of 1 min of kumikata fight (i.e., grip fight), and 2 sets of 10 repetitions of nagekomi (i.e., practice throws) [6]. The other two experimental conditions included conditioning activities in addition to the judo-specific warm-up. The first conditioning activity included performing one set of 3RM back squats with ~90% 1RM load [8]. The second conditioning activity included performing ballistic jump exercises, i.e., squat jumps, scissor jumps, and double leg bounds [14]. Following each experimental condition, the participants performed the SJFT after an approximately eight-minute rest period [15]. Immediately upon completion of the SJFT, heart rate was measured, followed by a one-minute post-exercise heart rate measurement. Subsequently, the handgrip strength and RPE scores were assessed ~3 min and ~30 min after SJFT, respectively. Figure 1 presents a schematic representation of the study.

2.5. The Special Judo Fitness Test (SJFT)

The SJFT is a reliable (Cronbach alpha = 0.81 for the SJFT index) [16] assessment for judo-specific performance. The test was administered by the standardized protocol outlined by Sterkowicz [17], which necessitates the participation of three athletes with comparable body mass. The central athlete, referred to as the TORI, is positioned between two assistants, or UKEs, who are placed 3 m apart on either side and are similarly matched in body mass to ensure consistency in the performance demands. Following a passive rest period of eight minutes after both the control and experimental conditions, the test commenced. At the signal of the assessor, the TORI alternates between the two UKEs, performing the Ippon Seoi-Nage throw technique as quickly as possible. The test comprises three sets: an initial 15-s set, then two 30-s sets, with 10-s rest intervals between the second and third sets. The objective is to maximize the number of throws executed within these timeframes, mimicking the high-intensity efforts characteristic of judo competitions. Three researchers carried out data collection: two recorded the number of throws executed on each UKE, while the third monitored the timing of the test. Heart rate was continuously monitored using a Polar H10 monitor (Kempele, Finland) connected to the Polar Beat app (version 3.5.9), with heart rate readings taken during the test immediately following its conclusion and a one-minute post-test. The SJFT index, the primary performance metric, was calculated by adding the immediate post-test heart rate and the heart rate recorded one minute later and dividing the sum by the total number of throws. A lower SJFT index indicates superior performance, as it reflects an athlete’s ability to sustain explosive efforts while maintaining an efficient cardiovascular response [18].

2.6. Handgrip Strength

The maximum isometric handgrip strength was assessed on each hand, alternating sides, with a one-minute rest between attempts [19]. During each trial, athletes were instructed to exert the maximum force possible for 3 to 5 s while standing, with their elbows fully extended and wrist positions chosen by themselves. These measurements were taken using a reliable (interclass correlation coefficient = 0.79 for left hand and 0.85 for right hand) Jamar dynamometer (Jamar, Lafayette, CA, USA). Only one maximal trial was conducted.

2.7. Rating of Perceived Exertion (RPE)

The RPE of participants was measured using the Borg 10-point scale, as adapted by Foster, et al. [20]. This scale provides a single numerical value that indicates the internal training load in arbitrary units. Before the experiment commenced, participants were instructed and became accustomed to using the Borg 10-point scale. After completing each warm-up protocol, approximately 30 min later, participants were asked to rate the overall difficulty of the exercise, and their RPE values were recorded.

2.8. Statistical Analyses

The data are presented as mean and standard deviations. Before conducting statistical analysis, we checked the data for normality using the Shapiro–Wilk test. For non-normally distributed data, we performed a two-way transformation [21]. We used repeated measures analysis of variance to analyze the difference between the different experimental conditions. When a significant difference was observed using repeated measures analysis of variance, we conducted post hoc analysis using multiple t-tests with Bonferroni corrections. Partial eta squared (η_p²) values derived from the repeated measures analysis of variance output were used as effect size (ES) scores. Further, Hedges’ g (t-test ES) was calculated to assess the magnitude of the difference between groups. The magnitude of effects for η_p² was interpreted as small (<0.06), moderate (≥0.06–0.13), and large (≥0.14) [22], while Hedge’s g was interpreted as trivial (<0.2), small (0.2–0.6), moderate (>0.6–1.2), or large (>1.2–2.0) [23]. Percentage change scores between experimental and control conditions were also calculated for each variable. All statistical analyses were performed using SPSS version 26, and the significance level was set at 0.05 for all analyses.

3. Results

The means and standard deviations for all variables are presented in

Table 1. Descriptive statistics and results of statistical analysis comparing the three conditions.

	Control	Squats	Ballistic Jumps	RMANOVA
	Mean ± Standard Deviation/Median (Interquartile Range)			F-Value	p-Value	ηp2
Throws in set 1	4.00 (1.00)	5.00 (1.25)	5.00 (0.25)	3.53	0.051	0.28
Throws in set 2	8.00 (1.00) *#	9.70 ± 0.95	9.50 (1.25)	16.46	<0.001	0.65
Throws in set 3	9.00 (1.00)	9.20 ± 0.92	9.00 (2.00)	1.88	0.181	0.17
Total throws	21.30 ± 0.95 *#	23.90 ± 2.13	24.0 (3.25)	20.62	<0.001	0.70
HR immediate	184.9 ± 11.98	190.7 ± 7.54	181.90 ± 13.75	3.72	0.076	0.29
HR one-minute	154.9 ± 15.2	156.7 ± 12.5	150.1 ± 14.3	1.23	0.303	0.12
SJFT index	16.0 ± 1.5 *#	14.7 ± 1.6	14.4 ± 1.9	16.34	<0.001	0.65
Handgrip right	30.1 ± 6.2 *	28.8 ± 6.6 ¥	30.4 ± 6.5	12.25	<0.001	0.58
Handgrip left	29.4 ± 6.5	25.45 (9.00)	29.9 ± 6.7	2.96	0.110	0.25
RPE	7.1 ± 1.0	6.5 ± 1.1	6.4 ± 1.0	1.78	0.197	0.20

Note: Medians and interquartile ranges are presented for data showing non-normal distribution, *—significant difference between control and squat group, ^#—significant difference between control and plyometric group, ^¥—significant difference between squat and plyometric group, η_p²—partial eta squared. Control—control condition, squats—squat-based conditioning activity, ballistic jumps—ballistic jump-based conditioning activity, HR—heart rate, SJFT—special judo fitness test, RPE—rating of perceived exertion.

with a graphical presentation of percentage difference between experimental conditions and control in Figure 2. For non-normally distributed data (i.e., throws in set 1, throws in set 2, throws in set 3, total throws, and left-hand grip strength), data are presented as median and interquartile range. The mean and standard deviation of the non-normal data are as follows: throws in set 1 (control: 4.40 ± 0.52; squat: 5.00 ± 0.94; ballistic jumps: 4.90 ± 0.57), throws in set 2 (control: 8.20 ± 0.63; ballistic jumps: 9.30 ± 0.82), throws in set 3 (control: 8.70 ± 0.48; ballistic jumps: 9.00 ± 0.82), total throws (ballistic jumps: 23.20 ± 1.62), and handgrip strength of left hand (squat: 27.9 ± 6.8). In the SJFT, the results revealed significant differences between the experimental conditions for throws in set 2 (F = 16.46; p < 0.001, η_p² = 0.65, large ES), total throws (F = 20.62; p < 0.001, η_p²= 0.70, large ES), and the SJFT index (F = 16.34; p < 0.001, η_p² = 0.65, large ES). Both the squat and ballistic jump exercises significantly improved performance compared to the control condition. For throws in set 2, significant improvements were observed following both the squat (p = 0.003, Hedge’s g = 1.78, large ES) and ballistic jump exercises (p = 0.010, Hedge’s g = 1.44, large ES). Similarly, total throws were significantly higher in the squat (p = 0.003, Hedge’s g = 1.51, large ES) and ballistic jump (p < 0.001, Hedge’s g = 1.37, large ES) conditions compared to the control. The SJFT index also showed improvements for both the squat (p = 0.010, Hedge’s g = 0.80, moderate ES) and ballistic jump (p < 0.001, Hedge’s g = 0.90, moderate ES) conditions. However, no significant differences were found between the squat and ballistic jump conditions for the throw in set 2, total throws, or the SJFT index. Additionally, there were no significant differences in throws in set 1, throws in set 3, or heart rate measurements (immediate and one-minute post-test) among the three experimental conditions.

Regarding handgrip strength, a significant reduction in right-hand grip strength was observed following the squat condition compared to both the control (p = 0.008, Hedge’s g = 0.19, trivial ES) and the ballistic jump condition (p = 0.014, Hedge’s g = 0.23, small ES), while no differences were found between ballistic jumps and control for right-hand grip strength. There were no significant differences in left-hand grip strength or RPE across any of the conditions.

4. Discussion

This study aimed to investigate the effects of two different conditioning activities (i.e., squat and ballistic jumps) on judo-specific performance (i.e., SJFT), handgrip strength, and RPE scores among young judo athletes. The findings suggest both squat and ballistic jumps as conditioning activities improved judo-specific performance, evidenced by the increased number of throws in set 2, total number of throws, and improved SJFT index compared to a control condition. In addition, squatting as a conditioning activity resulted in reduced handgrip strength of the right hand compared to ballistic jumps or control conditions. No significant difference was noted between squat and ballistic jump conditioning activities for other dependent variables.

Compared to a control condition (i.e., judo specific warm-up), both squat and ballistic jumps as conditioning activities were effective in increasing the number of throws during set 2 and the total number of throws. In addition, both the conditioning activities improved the SJFT index compared to the control condition. These improvements may be attributed to the mechanism underlying the PAPE effect [5]. For example, increased muscle temperature, intramuscular fluid accumulation (i.e., muscle blood flow and/or water), decreased muscle pH, and increased neural drive (i.e., greater muscle activation) are the suggested mechanisms for the PAPE effect. In addition, the significant improvement in the number of throws after the ballistic jump exercise can be attributed to the enhanced motor efficiency during the execution of maximal effort repetitions in workouts [24]. The ballistic jump exercise is suggested to enhance the neural stimulation to a higher level because higher threshold motor units are recruited only when high power outputs are demanded [25]. These higher-order motor unit activations may have resulted in the heightened neural stimulation of muscle, thus augmenting power production [8]. Moreover, ballistic exercises are suggested to selectively activate the type II motor unit fibers [26], that underlie power production in athletes, which is essential during the performance of the throws during the SJFT. Indeed, ballistic exercise, when applied over a longitudinal period (i.e., training interventions), is associated with observed improvements in combat athletes’ physical fitness performance [27]. Moreover, the results obtained in the current study are in line with previous studies that used ballistic exercises as conditioning activities on judo athletes [6,7]. Improvements in throws and the SJFT index were reported after box jumps with incremental height (i.e., 20 cm to 40 cm to 60 cm) [7] as well as after standing broad jumps [6].

Furthermore, the improved performance in the SJFT after squatting as a conditioning activity may be attributed to mechanisms similar to that suggested for ballistic jump exercises (please read the previous paragraph). However, the current findings do not align with a previous study that includes squats as a conditioning activity [7]. Miarka, Del Vecchio, and Franchini [7] used 5 repetitions of 95% 1RM squats with a 2-minute rest between each repetition and reported no changes in SJFT performance compared to the control condition. One of the plausible differences in the findings may be associated with the rest between the conditioning activity and the performance of the SJFT. Miarka, Del Vecchio, and Franchini [7] used a recovery period of 3 min, whereas in the current study, a recovery period of 8 min was used. It is important to note that the PAPE effect is an interplay between fatigue and potentiation [5]. Indeed, to achieve a PAPE effect, an optimal recovery duration between the conditioning activity and performance is suggested. The balance between these two effects determines overall performance, and when fatigue outweighs potentiation, performance declines [28,29]. Of note, recent studies have consistently advocated the use of a longer recovery duration after a heavy resistance exercise compared to a ballistic exercise as a conditioning activity [5].

Of note, our findings reported a significant difference between conditioning activities and control conditions during throws in set 2 but not in sets 1 and 3, which is in contrast to previous findings [6,7]. For example, Miarka, Del Vecchio, and Franchini [7] reported a significant difference during throws in set 1 but not in sets 2 and 3 after plyometric conditioning activity compared to a control condition. Similarly, Lum [6] reported significant differences after conditioning activities (i.e., lower-body exercises and upper-body combined with lower-body exercises) compared to control conditions during throws in sets 1 but not in sets 2 and 3. Although speculative, a plausible explanation may be the longer duration of recovery (compared to previous studies that used 3 min and 5 min [6,7]) between the conditioning activities and the SJFT assessment. It may be plausible that although 8 min of recovery between the conditioning activities and the SJFT seems optimal, the first set of throws lasting 15 s may have acted as a re-warm-up strategy for the athletes, thus increasing the number of throws in set 2. Miarka, Del Vecchio, and Franchini [7] used a shorter recovery duration of 3 min and thus showed improved the performance in set 1 of the SJFT after plyometric conditioning activity (possibly not requiring a re-warm-up activity). However, in the same study [7], the authors did not report improvement in throws (during sets 1, 2, 3, and total) after maximal strength and contrast pair of exercises, underlying the importance of consideration of recovery duration based on the type of conditioning activities used. In addition, Lum [6] included a 3RM high-pull test (to measure power output) as a performance measure after 5 min of conditioning activities that was followed by the SJFT after 2 min. It may be plausible that the 3RM high-pull test acted as a re-warm-up strategy before the SJFT was performed at approximately 7 min after the main conditioning activity was performed [6]. Indeed, these aforementioned reasons may also explain the non-significant difference during throws in set 2 in previous studies [6,7], i.e., potentiation effects during throws in set 1 but fatigue during throws in sets 2 and 3. Whereas, in our study, the throws during set 1 acted as a re-warm-up strategy, whilst potentiation effects were observed in set 2 and fatigue effects in set 3. However, this remains speculative, and the readers are suggested to be cautious until further research confirms our hypothesis.

The physiological responses measured using the HR immediately and one minute after the SJFT showed no significant difference between the experimental conditions. This finding aligns with previous studies [6,7], where both the immediate HR and HR after one minute did not show significant differences between the experimental condition and control. This suggests that the conditioning activities, in general, do not have any acute effect on cardiovascular recovery. Another finding was a decrease in the handgrip strength after the squat-based conditioning activity, compared to the ballistic jump or control condition. A possible reason for this finding may be the activation of trunk muscles during the execution of the squat exercise [30]. It was reported that a higher activation of trunk muscles was observed with loads greater than 50% 1RM [30]. Therefore, it may be possible that the participants were fatigued due to repeated exposure of the trunk muscles during judo-specific warm-ups, squats (as conditioning activity), and three sets of throws during the SJFT, resulting in higher fatigue compared to the ballistic jump exercise (that used the lower body conditioning activity) and control condition (that did not use any additional conditioning activity). Further, no difference was noted in the handgrip strength of the left hand. This may be plausible due to the extensive use of the right arm for throws during the SJFT assessments by the participants. Although the participants were allowed to select the preferred side of the throw, it was observed that most participants used the right side during the throws. Lastly, no significant difference was noted in RPE between the experimental conditions. These findings show that the addition of the additional stimulus using conditioning activities did not induce any additional psychophysiological stress on the participants, thus suggesting effective utilization of these exercises as conditioning activities to induce the PAPE effects without increasing the perceived effort.

4.1. Limitations

While this study provides valuable insights into the effects of squat and ballistic jump exercises on judo-specific performance, several limitations should be noted. First, although the sample size was estimated using a priori calculations, the small sample size (n = 10) limits the generalizability of the findings to a broader population of young judokas. A larger sample size would enhance the statistical power and improve the reliability of the results. Second, the study only included male participants, which restricts the applicability of the findings to female judokas. Future research should explore whether similar results are observed in female athletes or across different age groups and competition levels. Third, we used squats and ballistic jumps as conditioning activities and a recovery time of 8 min. Of note, previous studies [5,31] have suggested that PAPE could be moderated by the type of conditioning activities, exercise type, loading, recovery interval, performance parameters, etc. Therefore, future research should focus on various moderating factors that could potentially affect PAPE in judo. Fourth, the focus was on immediate performance effects rather than the long-term impact of repeated conditioning activities. While the study assessed acute performance improvements, it remains unclear how consistent use of these exercises in training over time would affect performance, fatigue, and injury risk. Future studies could explore the chronic effects of incorporating these conditioning exercises into regular training programs. Fifth, the study measured handgrip strength but did not assess other important physical parameters, such as lower body power or muscle fatigue, which could provide a more comprehensive understanding of how these exercises influence judo-specific performance. Incorporating a broader range of performance and physiological measures in future research would help clarify the full scope of the impact of conditioning activities. Lastly, although a randomized crossover study design was adopted to minimize the confounding effects of extraneous variables on the results, controlled laboratory conditions (e.g., temperature) could be an appropriate setting.

4.2. Practical Applications

While this study has some limitations, it provides valuable insights into the benefits of incorporating squat and ballistic jump exercises into warm-up routines for young judokas. The study suggests that both squat and ballistic jump exercises can effectively improve the performance of young judokas in the SJFT. For youth athletes, ballistic jumps like squat jumps, scissor jumps, and double-leg bounds are preferred for enhancing explosive power and total throws without causing upper-body fatigue. These exercises offer significant benefits, especially in the second set of the SJFT, while maintaining handgrip strength, which is crucial for gripping and throwing techniques. Squats, on the other hand, should be used carefully when handgrip strength is essential. For sessions or competitions requiring grip-intensive techniques, practitioners should either reduce the volume of squat-based conditioning or allow sufficient recovery between squat exercises and performance to minimize the risk of upper body fatigue. Coaches should consider alternating between ballistic and squat-based conditioning activities based on the athlete’s specific needs and the training or competition phase. Both exercises can enhance judo-specific performance when used strategically. Ballistic exercises may be particularly beneficial for pre-competition warm-ups due to their lower risk of fatigue, while squats may be better suited for strength-focused training sessions with proper recovery. Future research should build on these results to further refine training protocols and optimize performance in youth judo.

5. Conclusions

This study demonstrated that incorporating squat and ballistic jump exercises into a warm-up routine significantly improves judo-specific performance in young male judokas, particularly in the number of throws and the SJFT index. These conditioning activities caused PAPE without significantly increasing RPE. However, the squat-based activity resulted in decreased handgrip strength in the right hand, indicating localized fatigue. Nevertheless, there were no significant differences in left-hand grip strength or RPE between the experimental conditions. These findings support the use of both squat and ballistic jump exercises as effective conditioning activities to enhance judo-specific performance, especially in young athletes. However, caution should be taken when including squats due to their potential to induce upper-body muscle fatigue, which may impact grip strength during competition.