Abstract
of this study was to examine the effects of an 8-week core training program on the lower-extremity, upper-extremity, and core strength of judokas. Methods: This study is based on a pre-test/post-test experimental design involving repeated measures and a control group. The study was conducted with the voluntary participation of 20 judo athletes (10 females and 10 males) aged between 18 and 22 years (mean age: 18.60 years; height: 163 cm; body weight: 59.40 kg; BMI: 22.30 kg/m 2 ). Participants were divided into two groups: a control group that continued routine judo training and an experimental group that performed core training in addition to routine judo training. Participants performed Medial Push-Ups (MPUs) to assess upper-extremity muscle strength; sit-ups and Plank Tests (PTs) to assess core strength; five different Single-Leg Hop Tests (SLHTs) to assess lower-extremity muscle strength; and the Y Balance Test (YBT) to assess balance. These tests were conducted before and after the 8-week core training program. Results: PT performance improved significantly in both groups, with a significant group×time interaction (p< 0.001, η 2p = 0.623), indicating greater improvement in the core training group
strength; five different Single-Leg Hop Tests (SLHTs) to assess lower-extremity muscle strength; and the Y Balance Test (YBT) to assess balance. These tests were conducted before and after the 8-week core training program. Results: PT performance improved significantly in both groups, with a significant group×time interaction (p< 0.001, η 2p = 0.623), indicating greater improvement in the core training group compared to the control group. No significant interaction was observed for MPU and Sit-up tests; however, a significant main effect of time was detected for MPU (p= 0.032,η 2p = 0.231), suggesting general improvements in both groups. For SLHT parameters, no significantgroup×time interactions were detected (p> 0.050); improvements were observed over time across groups. In balance performance, a significant group×time interaction was found only in the NDS postero-medial (PM) direction (p= 0.020,η 2p = 0.267), whereas the other parameters demonstrated time-related improvements without between-group differences. Conclusions: Core stability training resulted in greater improvements in PT performance and influenced balance performance in the NDS PM direction. Improvements observed in other performance parameters appeared to be time-related rather than intervention-specific. Overall, core stability training may contribute to core endurance and certain aspects of lower-extremity function in judokas. Keywords:balance; core training; combat sports; hop tests; judo Appl. Sci.2026,16, 2013 https://doi.org/10.3390/app16042013
Appl. Sci.2026,16, 2013 2 of 15 1. Introduction Judo is an Olympic combat sport that requires the coordinated use of multiple physical parameters, including strength, balance, and agility [1]. To respond rapidly and accurately to unpredictable forces during competition, judo athletes must possess advanced levels of body control [2]. Under the continuously changing conditions of competition, trunk stability and alignment emerge as important determinants of both overall and technical performance in judo athletes [1,3]. The core region, which functions as the central link of the kinetic chain, consists of the abdominal and spinal muscles, as well as the hip and diaphragm muscles [4]. The core region plays a critical role in the efficiency of force transfer between the lower and upper extremities and supports spinal stabilization and postural control, particularly during dynamic movements [5]. The technical demands and competitive conditions of judo require sudden changes in direction and asymmetric strength loading [6]. Core stability provides a fundamental basis for the efficient transmission of these sudden and asymmetric strengths during competition, thereby enabling the execution of technical performance at a high level [1,3]. In addition, dynamic balance and both upper and lower-extremity functionality emerge as other important performance-related factors in judo athletes [1]. The sport-specific demands of judo have also been a determining factor in previous research conducted in this field. Accordingly, the relationships between core training and various physical performance components in judo athletes have been examined in several studies [3,7–10]. These studies have reported that core training may lead to significant improvements in judo athletes, particularly in terms of dynamic balance [3,9]. In addition, various functional tests, such as single-leg hop tests (SLHT), are commonly used in the literature to evaluate functional lower-extremity capacity and neuromuscular control in judo athletes [3,11]. Previous studies have emphasized the importance of examining these physical parameters in the assessment of judo-specific technical and physical performance, as well as in monitoring training effects [2,8,10]. However, a review of the existing literature reveals that most studies focus solely on isolated performance measures such as balance or general strength [3,9]. Consider- ing the asymmetric, multifunctional, and
athletes [3,11]. Previous studies have emphasized the importance of examining these physical parameters in the assessment of judo-specific technical and physical performance, as well as in monitoring training effects [2,8,10]. However, a review of the existing literature reveals that most studies focus solely on isolated performance measures such as balance or general strength [3,9]. Consider- ing the asymmetric, multifunctional, and highly variable technical structure of judo, it is noteworthy that randomized controlled trials simultaneously evaluating the integral structure of core stability with rapid changes in direction, explosive strength transfer, and lower-extremity functionality have not been sufficiently investigated in this field [3,5,11]. Therefore, the effects of core stability training on trunk endurance, upper-extremity muscle endurance, multidirectional dynamic balance, and functional lower-extremity performance have not been sufficiently addressed in young competitive judo athletes. In this regard, the present study aimed to provide a comprehensive assessment fo- cusing primarily on performance and function-related outcomes rather than maximum muscle strength. In this context, core stability within judo’s sport-specific movement de- mands was reflected by evaluating trunk endurance, upper-extremity muscle endurance, lower-extremity functional performance, and multidimensional dynamic balance. Therefore, the purpose of this study is to examine the effects of an 8-week core training program on selected performance-related parameters in judo athletes aged 18–22 years. It was hypothesized that the 8-week core training intervention would lead to significant improvements in the selected functional performance outcomes. 2. Materials and Methods 2.1. Study Design This study employed a pre-test/post-test experimental design with repeated measures and a control group. Participants visited the laboratory five times. During the first visit, https://doi.org/10.3390/app16042013
Appl. Sci.2026,16, 2013 3 of 15 participants were informed about the training program and testing procedures to be applied, and they were encouraged to familiarize themselves with the tests. Anthropometric measurements, including age, height, body weight, and body mass index (BMI), were obtained from all volunteers who agreed to participate in the study. During the second and third visits, participants completed pre-test assessments, which included the SLHT, Y Balance Test (YBT), Medial Push-Up Test (MPU), Sit-Up Test, and Plank Test (PT). Pre-test measurements were conducted based on the participants’ selections from randomly assigned exercise cards. The distribution of tests across the randomly selected exercise cards was as follows: Card 1 included the single leg hop for distance (SH), triple hop for distance (TH), crossover hop for distance (CH), medial side triple hop for distance (MSTH), 90 ◦ medial rotation hop for distance (MRH), and the Sit-up; Card 2 included the YBT, MPU and PT. A 5 min rest period was provided between tests, and, upon the participant’s request, rest intervals were extended up to twofold. Prior to testing, participants completed a standardized 15 min warm-up protocol consisting of dynamic stretching and mobilization exercises. To minimize the effects of acute fatigue, neuromuscular activation changes, and transient performance fluctuations, participants were given a 48 h rest period between pre-test sessions and before the initiation of the intervention period [12]. Following the rest period, the experimental group performed an 8-week core training program in addition to their regular judo training (Table), whereas the control group con- tinued with only their routine judo training. Both groups continued with the same routine judo training. At the end of the intervention period, participants revisited the laboratory for the fourth and fifth times to complete the post-test assessments. The researchers responsible for data collection and data analysis were independent of each other, and researchers in both groups were blind to the participants’ group assignment. Post-test procedures were conducted in the same manner as the pre-test protocol (Figure). Table 1.8-week core training program. Week Day Exercises Sets Duration 1 1 Plank, Dead Bug, Glute Bridge, Russian Twist, Bird
assessments. The researchers responsible for data collection and data analysis were independent of each other, and researchers in both groups were blind to the participants’ group assignment. Post-test procedures were conducted in the same manner as the pre-test protocol (Figure). Table 1.8-week core training program. Week Day Exercises Sets Duration 1 1 Plank, Dead Bug, Glute Bridge, Russian Twist, Bird Dog 2 30 s2 Side Plank, Leg Raises, Mountain Climbers, Plank to Elbow, Glute Bridge 3 Dead Bug, Bird Dog, Russian Twist, Plank, Leg Raises 2 1 Plank, Hollow Hold, Side Plank, Glute Bridge, Russian Twist 2 30 s2 Bird Dog, Mountain Climbers, Bicycle Crunch, V-Ups, Leg Raises 3 Plank Jacks, Plank to Elbow, Glute Bridge, Dead Bug, Side Plank 3 1 Hollow Hold, Leg Raises, V-Ups, Plank, Russian Twist 3 30 s2 Plank Jacks, Bicycle Crunch, Glute Bridge, Side Plank, Bird Dog 3 Dead Bug, Mountain Climbers, Plank to Elbow, Hollow Hold, Russian Twist 4 1 Plank, Leg Raises, Side Plank (crunch), V-Ups, Plank Jacks 3 30 s2 Bicycle Crunch, Bird Dog, Russian Twist, Glute Bridge, Hollow Hold 3 Plank to Elbow, Mountain Climbers, Dead Bug, Plank, Side Plank 5 1 Plank Jacks, V-Ups, Russian Twist, Hollow Hold, Glute Bridge 3 35 s2 Bicycle Crunch, Bird Dog, Side Plank, Plank to Elbow, Mountain Climbers 3 Plank, Leg Raises, Dead Bug, Russian Twist, Plank Jacks 6 1 Hollow Hold, V-Ups, Side Plank (crunch), Glute Bridge, Mountain Climbers 3 35 s2 Bicycle Crunch, Plank Jacks, Leg Raises, Plank, Russian Twist 3 Dead Bug, Bird Dog, Plank to Elbow, Side Plank, V-Ups https://doi.org/10.3390/app16042013
Appl. Sci.2026,16, 2013 4 of 15 Table 1.Cont. Week Day Exercises Sets Duration 7 1 Hollow Hold, Plank Jacks, Bicycle Crunch, Glute Bridge, Side Plank 3 40 s2 Plank, Russian Twist, Bird Dog, V-Ups, Leg Raises 3 Mountain Climbers, Plank to Elbow, Dead Bug, Hollow Hold, Glute Bridge 8 1 Hollow Hold, Plank Jacks, Bicycle Crunch, Side Plank, Leg Raises 3 40 s2 V-Ups, Glute Bridge, Russian Twist, Bird Dog, Plank 3 Mountain Climbers (fast), Plank to Elbow, Dead Bug, Plank Jacks, Side Plank Rest between exercises: 30 s. Rest between sets: 2 min. Figure 1.Flowchart. All measurement sessions were conducted at the same time of day (12:00–14:00) and under similar environmental conditions. Participants were instructed to refrain from strenuous physical activity and from consuming stimulants such as caffeine for at least 48 h prior to testing. The study was conducted in accordance with the ethical principles outlined in the Declaration of Helsinki. This study was approved by the Alanya Alaaddin Keykubat University Non-Interventional Clinical Research Ethics Committee (approval number: 2025/08). Informed consent forms were obtained from all participants. 2.2. Participants The study was conducted with the voluntary participation of 20 judo athletes (10 femalesand 10 males) aged between 18 and 22 years (mean age: 18.60 years; height: 163 cm; body weight: 59.40 kg; BMI: 22.30 kg/m 2 ) (Table). Sample size was determined https://doi.org/10.3390/app16042013
Appl. Sci.2026,16, 2013 5 of 15 using a priori power analysis performed with G*Power software (version 3.1.9.6, Germany), with an effect size of d = 0.8, a significance level ofα= 0.05, and a statistical power of 1−β= 0.80, indicating a minimum required sample size of 16 participants. Inclusion criteria were as follows: actively participating in judo training, having a minimum of five years of regular judo training experience, and no history of serious sports-related injury within the preceding six months. Participants who did not meet the inclusion criteria or who chose to withdraw from the study at any stage were excluded from the analysis. Participants were allocated to either the experimental group (n = 10) or the control group (n = 10). To ensure homogeneity between groups, demographic and anthropometric char- acteristics, including sex, age, training experience, height, body weight, and BMI, were taken into consideration. Matched pairs with similar characteristics were formed, and one participant from each pair was assigned to the experimental group and the other to the control group using a computer-assisted randomization procedure. This approach minimized potential between-group differences prior to the intervention. Written informed consent was obtained from all participants prior to their inclusion in the study. Table 2.Descriptive data. Experimental (n = 10) Mean±SD Control (n = 10) Mean±SD p Age (year) 18.60 ±0.84 18.50 ±0.71 0.777 Height (cm) 163 ±8.44 162.50 ±9.54 0.903 Weight (kg) 59.40 ±11.42 56.90 ±12.94 0.652 BMI (kg/m 2 ) 22.30±3.88 21.30 ±3.11 0.534 Training age (year) 6.80 ±1.03 7 ±1.33 0.712 p< 0.05; SD: standard deviation; BMI: body mass index. 2.3. Procedures 2.3.1. Anthropometric Measurements Body weight was measured to the nearest 0.1 kg using a body composition analyzer (Jawon Body Composition Analyser Model X-Scanplus II, Seoul, Republic of Korea), and height was measured to the nearest 0.1 cm using a stadiometer (Holtain Ltd., Crymych, UK). All measurements were performed barefoot in the anatomical position [13]. BMI was calculated using the formula body weight (kg)/height (m 2 ). 2.3.2. Single Leg Hop Tests (SLHT) SLHTs were performed on a flat surface in the laboratory using a measuring tape
of Korea), and height was measured to the nearest 0.1 cm using a stadiometer (Holtain Ltd., Crymych, UK). All measurements were performed barefoot in the anatomical position [13]. BMI was calculated using the formula body weight (kg)/height (m 2 ). 2.3.2. Single Leg Hop Tests (SLHT) SLHTs were performed on a flat surface in the laboratory using a measuring tape fixed to the floor (length: 6 m; width: 15 cm). At the starting phase of each test, participants posi- tioned the toes of the tested foot at the starting line of the measuring tape and maintained balance on a single leg [dominant (DS) or non-dominant (NDS)] before initiating the test at a self-selected time. During the execution phase, arm swing was permitted, and successful trials were defined as those in which participants were able to maintain single-leg balance for 3 s following landing. In the SH test, participants performed one maximal hop; in the TH test, three consecutive hops were performed. In the CH test, participants completed three consecutive hops in a crossover pattern, landing alternately on the opposite side of the initial hop direction. For the MRH test, participants placed the medial border of the foot at the starting line of the measuring tape and, once ready, performed a single medial hop following a 90 ◦ medial rotation. In the MSTH test, participants similarly positioned the medial border of the foot at the starting line and performed three consecutive hops in the medial direction. https://doi.org/10.3390/app16042013
Appl. Sci.2026,16, 2013 6 of 15 Participants completed three practice trials before the main testing session. For the main trials, the distance between the heel at landing and the starting line of the measuring tape was recorded in centimeters for all successful attempts [14–16]. 2.3.3. Y Balance Test (YBT) YBT was performed on three 15 cm-wide strips arranged on the floor in a Y-shaped configuration, oriented in the anterior (ANT), posteromedial (PM), and posterolateral (PL) directions. The angle between the ANT and PM directions, as well as between the ANT and PL directions, was 135 ◦ , while the angle between the PM and PL directions was 90 ◦ . During the execution phase, participants were instructed to place the stance foot at the zero-mark position, extend the contralateral limb as far as possible in the designated reach direction, and then return the reaching limb to the starting position. ANT reach distances were recorded as the distance (cm) from the toe of the stance foot to the point of maximal reach, whereas PM and PL reach distances were measured from the heel of the stance foot to the point of maximal reach. A trial was considered successful if participants were able to return the reaching limb to the starting position while maintaining balance on the stance limb. Participants performed three trials in each direction, and the mean of the reach distances was recorded for analysis [17]. 2.3.4. Medial Push up Test (MPU) MPU was used to assess upper-body muscular endurance. At the start of the test, participants placed their hands shoulder-width apart on a flat surface and positioned their bodies in a straight line from head to heels, with their toes in contact with the ground. During the execution phase, participants flexed their elbows to approximately 90 ◦ and then returned to the starting position. Each complete lowering and raising movement was counted as one repetition, and the total number of correctly performed repetitions completed within 30 s was recorded [18]. 2.3.5. Sit-Up Test The Sit-up test is a field-based assessment used to evaluate the muscular endurance of the core
participants flexed their elbows to approximately 90 ◦ and then returned to the starting position. Each complete lowering and raising movement was counted as one repetition, and the total number of correctly performed repetitions completed within 30 s was recorded [18]. 2.3.5. Sit-Up Test The Sit-up test is a field-based assessment used to evaluate the muscular endurance of the core region. During the preparation phase, participants lay supine on a flat surface with their knees flexed at approximately 90 ◦ . The feet remained in contact with the ground, and the arms were crossed over the chest. Upon the start command, participants lifted the trunk off the surface and, once approaching the thighs, returned to the starting position in a controlled manner. Each complete movement was counted as one repetition, and the total number of correctly performed repetitions completed within 30 s was recorded [19]. 2.3.6. Plank Test (PT) The PT is a field-based assessment used to evaluate trunk stabilization and the isomet- ric endurance of the core muscles. At the start of the test, participants assumed a prone position on a flat surface, with the elbows positioned directly under the shoulders and the forearms and toes in contact with the ground. The body was aligned in a straight line. During the execution phase, timing commenced, and participants were instructed to maintain body stabilization for as long as possible without altering the initial position. The test was terminated when proper plank alignment could no longer be maintained. The total duration for which the correct position was sustained was recorded in seconds [20]. 2.4. Statistical Analysis Statistical analyses were performed using the SPSS software package (version 25.0; IBM Corp., Armonk, NY, USA). Descriptive data are presented as mean±standard deviation. https://doi.org/10.3390/app16042013
Appl. Sci.2026,16, 2013 7 of 15 Data normality and homogeneity of variances were assessed using the Shapiro–Wilk test, Q–Q plots, and Levene’s test, respectively. Although the sample size was small, visual inspection and statistical tests indicated no significant deviations from normality. A 2×2 mixed-model repeated-measures analysis of variance (ANOVA) was employed to examine the effects of time (pre vs. post) and group (experimental vs. control), as well as time ×group interaction effects. When a significant main effect or interaction was detected, Bonferroni-adjusted post hoc tests were conducted to identify the source of the differences. Post hoc pairwise comparisons (paired-samplest-tests) were performed only for variables showing a significant Group×Time interaction. To determine the magnitude of the differences, effect sizes were calculated. Partial eta squared (η 2p) was reported for the ANOVA main and interaction effects, classified as small (0.01), medium (0.06), and large (0.14). For pairwise comparisons (t-tests), Cohen’s dzwas calculated and interpreted as trivial (<0.2), small (0.2–0.5), moderate (0.5–0.8), and large (>0.8). The level of statistical significance was set atp< 0.05. 3. Results Descriptive characteristics of the participants are presented in Table. Figure the intervention. A significant group×time interaction was observed for the PT parameter (p< 0.001,η 2p = 0.623), indicating a differential change between groups. Additionally, a significant main effect of time was found (p< 0.001,η 2p = 0.818). Post hoc analyses revealed significant improvements in both the experimental group (p= 0.001, dz= 2.556) and the control group (p= 0.003, dz= 1.250), indicating very large and large effect sizes, respectively. Figure 2.Comparison of pre- and post-intervention changes in the MPU, Sit-up, and PT performances. *p< 0.05. No significant group×time interaction was observed for the other parameters (p> 0.050). For the MPU parameter, although the interaction was not significant, a signifi- cant main effect of time was detected (p< 0.032,η 2p = 0.231), suggesting that both groups improved similarly over time. Figure ter the intervention. No significant group×time interaction was observed for any pa- rameter (p> 0.05,η 2p < 0.064), indicating that the magnitude of change did not differ between groups. https://doi.org/10.3390/app16042013
Description
This study evaluates the impact of core training on judo athletes' performance.