The comparison of the effects of post-activity performance enhancement on foot plantar pressure and vertical jump in traditional set and cluster set training configurations

2.1 Participants

A total of 27 male students (Age: 20.0 ± 1.2 years, height: 180.2 ± 6.9 cm, body weight: 76.0 ± 11.8 kg) studying at the School of Physical Education and Sports, aged between 18–22 years, who have not done strength exercise for at least six months, who have not participated in strength exercise tests before, and who do not have any health problems, participated in the study voluntarily. The target sample number of 27 participants was determined by G*Power software (Version: 3.1.9.7, Heinrich-Heine-Universitat Dusseldorf, Dusseldorf, NRW, Germany) based on the data entered as power size (1 − β) 0.80, type I error or error level α = 0.05 and effect size (d) 0.80. The participants were assigned to the test protocols in accordance with a simple randomization method between December 01, 2023 and February 15, 2024. Istanbul Nisantası University Ethical Committee approval (Reference number: 2021/13) was obtained for the study.

2.2 Study design

The measurement and test devices were calibrated before starting the tests on the participants, who signed the informed consent form before the study. Trial measurements and tests were applied to the participants in order to adapt to laboratory conditions, anthropometric measurements, half-squats with free weights, static foot plantar pressure (SFPP), countermovement jump (CMJ), and squat jump (SJ) tests. Before starting half-squats, the participants applied a 10-min warm-up protocol consisting of jogging, dynamic stretching, and calisthenic movements in shorts, t-shirts and sports shoes as they wished. On the fourth day after the trial measurements and tests, all participants were given anthropometric measurements consisting of height and body weight measurements, and then tests of half-squat 1 repetition maximum (HS 1RM), SFPP, CMJ and SJ as pre-tests (PRE). After 4 min of the HS 1RM test, and the SFPP test with both feet was performed three times with 1-min rest intervals. After the foot plantar pressure test and 8 min after the HS 1RM test, the PRE was completed with the CMJ and SJ tests, which were performed three times at 30 s rest intervals. After PRE, the participants performed 12 reps of half squats with 70% intensity of the HS 1RM determined in the PRE with 1 × 12 reps traditional set (TS) on the 4th day, 3 × 4 reps cluster set (CS1) with 30 s rest intervals on the 8th day, and 6 × 2 reps cluster set (CS2) with 10 s rest intervals on the 12th day. The bar velocity was measured in all sets. After finishing the set, the participant completed the static plantar pressure with both feet, as well as CMJ and SJ tests as re-tests with the same procedure applied in the PRE. The experimental design is given in Fig. 1.

Fig. 1.The experimental design of the study. HS 1RM: half-squat 1 repetition maximum.

2.3 Anthropometric measurements

Height measurements were made using a portable height meter with an accuracy of 0.1 mm (Seca 213, Vogel & Halke GmbH & Co, Hamburg, HH, Germany), and body weight measurements were made using an electronic laboratory scale with an accuracy of 0.1 kg (Seca 813, Vogel & Halke GmbH & Co, Hamburg, HH, Germany) as stated by Lohman et al. [26].

2.4 Half-squat 1 repetition maximum (HS 1RM)

For the HS 1RM tests, Olympic bars (Eleiko, Sweden) and free weights (Gainzmach, Turkey) were used. Safety control of the depth of the half-squat distance is ensured by the safety bars of the power rack (Gainzmach, Turkey). According to the 1RM protocol of Pallarés et al. [27], each participant descended to the ∼90° half-squat position with a controlled eccentric contraction while standing in an upright position and after waiting for 1.5 s with the contact of the Olympic bar on his shoulder with the safety bars of the power rack, he returned to the upright position by exhibiting concentric contraction at maximal speed. The test started with 10 min of warm-up with free jogging, dynamic stretches, and calisthenic movements, followed by ten reps of warm-up lifts with a 20 kg Olympic bar. Weights corresponding to an estimated 30% of 1RM were attached to the bar, and a 1RM half-squat lift was performed. After 2 min of rest, weights between 100 g and 20 kg were added, and the half-squat one rep was continued. The test was continued until the participant was unable to lift the weight without assistance (usually 4–6 attempts), and the maximum weight he could successfully lift was recorded as HS 1RM.

2.5 Static foot plantar pressure tests

For the SFPP test, the Zebris FDM platform and Zebris FDM 1.12 software (Zebris Medical GmbH, Isny im Allgaau, BW, Germany) were used, and the data were recorded on the computer at 100 Hz. Based on the recommendation of Scoppa et al. [28] that the recording time of posturographic parameters between 25 and 40 s is reliable, the test duration was determined as 30 s. During the test, the participants were asked to look at the target at a distance of 2 m for 30 s while standing with the arms on the sides of the torso, the feet shoulder-width apart and parallel to each other (standard standing posture), and SFPP applied to the platform was recorded during these 30 s. Each participant repeated the test three times with 1 min rest intervals, and the highest score was included in the statistical evaluation.

2.6 Vertical jump tests

For CMJ and SJ tests, OptoJump™ (Microgate, Bolzano/Italy) with 1 ms accuracy was used. The vertical jump heights of each participant in the CMJ and SJ tests were obtained depending on the flight time. Each vertical jump test was performed in three trials with 30 s rest intervals, and the highest vertical jump height was statistically evaluated. As stated by Bosco and Komi [29] for the CMJ test, the participants flexed the knees with their feet shoulder-width apart, bringing them to a knee angle of approximately 85° where they felt a comfortable starting position, and making a maximal vertical jump without waiting. For the SJ test, as stated by Bosco and Komi [29], the participants flexed the knees with their feet shoulder-width apart, felt a comfortable starting position, and reached the half-squat position, which is normally formed at a knee angle of about 85°, and made a maximal vertical jump without moving downwards after waiting for at least 2–3 s to prevent the pre-stretching in the muscles before the jump.

2.7 Bar velocity measurement

For the bar velocity measurement during the half-squat 12 repetitions of 1RM at 70%, a wireless velocity measurement device (VmaxPro VBT Tracker, Blaumann & Meyer Sports Technology, Magdeburg, ST, Germany) with a three-axis accelerometer, gyroscope and magnetometer was used, the validity and reliability of which was established by Held et al. [30] and Feuerbacher et al. [31]. The device was calibrated before each lift and then connected to a tablet computer (iPad Pro, 11th inch (3rd generation), version 16.6.1; Apple, Inc., Cupertino, CA, USA) via Bluetooth 5.0. After the sensor of the device was placed at 1/4 point of the bar, it was monitored and tracked along the half-squats with the Enode Pro application (version 2.0.5, BM Sports Technology GmbH, Magdeburg, ST, Germany) compatible with the device and recorded at a sampling rate of 200 Hz. For the test to be accepted, the participant’s half-squat descending distance was set to a minimum of 30 cm. Participants performed each half-squat repetition at maximum velocity.

2.8 Statistical analysis

The data obtained from the study were analyzed using the Jamovi statistical program (2.3.28.0, Stats Open Now). Skewness and Kurtosis and Shapiro-Wilk analysis were used for a normal distribution, and Mauchly’s Sphericity Test was used to measure the sphericity of all variables. In Mauchly’s Sphericality test, Greenhouse Geisser sphericity correction was preferred for the F value because the Epsilon value (ε) was less than 0.75 and the sample volume was low in the variables where the sphericity assumptions were not fulfilled. One-way analysis of Variance in Repeated Measurements (ANOVA) was used to compare the tests performed in four different time periods depending on three different strength training structures consisting of TS, CS1 and CS2. When the F statistics were significant for training-related changes, the Tukey Test was used in pairwise comparisons to determine which training variables caused the differences. Partial eta squared (η²) was calculated for the size of the trial effect. As stated by Richardson [32], partial η²; is classified as 0.01 = small, 0.06 = medium, and 0.14 = large impact. The statistical significance level was accepted as p < 0.05.

4.1 PAPE based on vertical jump due to TS and CS configurations

Regarding the different set configurations, Moreno et al. [33] reported that repetitive plyometric squat jumps performed with three different set configurations consisting of 2 × 10 reps of TS with 90 s rest between sets, 4 × 5 reps of CS1 with 30 s rest between sets, and 10 × 2 reps of CS2 with 10 s rest between sets allowed for greater maintenance of vertical jump power, take-off velocity and vertical jump height in CS, especially in CS2 compared to TS. In a similar study, Morales-Artacho et al. [34] found that a 3-week CMJ workout containing the CS configuration showed that the CMJ velocity and power adaptations specific to the training load were more effective in loading than the TS configuration. In the other study [18], resistance training, including squat lifting, was performed in 3 × 8 reps with 5 min rests and 6 × 4 reps with 2 min rests. CMJ decreased more in tests performed after 3 × 8 reps than after 6 × 4 reps. In the study of Asadi et al. [35], participants showed similar increases in CMJ in both groups after training 5 × 20 reps with 2 min rests as the TS configuration and 20 × (2 × 10 reps) with 1.5 min rest between each of 20 sets and 30 s rest between 2 sets as the CS configuration. However, the CMJ increase of CS was found to be higher than in TS. Although both training structures improved training performance at lower body maximal intensity, higher vertical jump adaptation occurred in the CS configuration. González-Hernández et al. [36] compared the mechanical, metabolic, and perceptual responses between two different TS (TS1 and TS2) and four different CS (CS1, CS2, CS3 and CS4) configurations. A balanced, randomized method was used to perform squat sessions with 30 reps, 5 min between sets, and a maximum of 10 reps. The set configurations were made equal as 3 × 10 reps with 5 min rests in TS1, 6 × 5 reps with 5 min rests in TS2, 3 × 10 reps with 10 s rests in CS1, 3 × 10 reps with 15 s rests in CS2, 3 × 10 reps with 30 s rests in CS3 and 1 × 30 reps with 15 s rests in CS4. Mechanical performance was tested by the average propulsive velocity during each rep and the change in CMJ after each set. In line with the average propulsive velocity results, the CMJ height showed the lowest reduction immediately after CS2 and CS3 compared to TS1. As a result of the increase in the number of sets, after each training set, there was a decrease in CMJ. In conclusion, it was determined that mechanical, metabolic, and perceptual fatigue was significantly higher in the TS1 configuration than in the CS configuration, and the 2 set configurations that minimize mechanical fatigue were CS2 and CS3. In their study comparing the acute effects of TS and two different CS configurations on neuromuscular and perceptual fatigue, Cuevas-Aburto et al. [37] employed the following experimental groups: the TS group performed 3 × 6 repetitions with 3 min of rest between sets; the CS1 group performed 3 × 6 repetitions with 30 seconds of in-set rest between every two reps and 3 min of rest between sets; and the CS2 group performed 9 × 2 repetitions with 45 seconds of in-set rest between every two reps. The study determined that set configurations had a statistically significant effect on the bar velocity. It was found that the average velocity of the sets and CMJ were lower in the TS group than in the CS1 and CS2 groups. Pareja-Blanco et al. [38] evaluated the effect of 10 set configurations in the number of reps performed in each set with respect to the maximum predicted number. Three sets with 5 min interset rests were performed in each configuration in bench press and squat, on CMJ, which is a mechanical muscle function from 24 h before to 48 h after exercise, at various time periods. Set configurations with more reps caused more decreases in CMJ due to more fatigue accumulation. The present study supported the results of these studies which suggest that longer set configurations led to greater metabolic responses, along with greater impairments in jump height after squats. Also, CS configurations allow for greater absolute velocity and power outputs, which are highly effective at reducing lactate accumulation and perceived exertion during resistance training [39]. In addition, longer set configurations resulted in higher blood lactate [36], ammonia, growth hormone, cortisol, and creatine kinase levels [40]. Although physiological parameters and perceived exertion were not tested in this study, the higher movement speed and power results related to the bar displacement at half squat 12 reps of 1RM at 70% showed that CS configurations were more effective lifting strategies for resistance training than TS. Therefore, it is thought that CS configurations may be very useful, especially in reducing mechanical fatigue, perceptual exertion, and metabolic stress. On the other hand, in the study conducted by Api et al. [7] to determine the effect of TS and CS configurations on mechanical and perceptual variables, squats were applied in the TS configuration including 3 × 8 reps with 225 s rest between sets, in the CS1 configuration including 3 × 2 × 4 reps with 30 s of in-set rests and 180 s rests between sets, and in the CS2 configuration including 3 × 4 × 2 reps with 30 s in-set rests and 90 s between sets. There was no statistically significant difference in CMJ after different set configurations. In the present study, the fact that all three of the TS, CS1 and CS2 configurations had statistically significant differences only with PRE supported the mentioned study. Iacono et al. [41] found a similar decrease in the CMJ performance of squats with TS and CS configurations with optimum power in the first 30 s, and an increase after 4 and 8 min. In addition, the CS configuration was found to produce higher CMJ compared to the TS configuration, which is similar to the results of the present study.

4.2 PAPE based on static foot plantar pressure due to TS and CS configurations

There is no study in the literature on the PAPE effect of resistance training using different set configurations with squat movements that can be exhibited at different joint angles on static foot plantar pressure variables. In this study, no statistically significant difference was found between the values of FC_avg, FC_max, 95% CEA and COPPL variables after three different resistance training set configurations consisting of TS, CS1 and CS2. This showed that the resistance training set configurations examined have similar effects on the variables of FC, 95% CEA, and COPPL. In the review study, Paillard [42] stated that static and dynamic activities increase the plantar pressure area. The plantar pressures of the feet during the spike jump showed that a certain sequence of foot contact correlated with performance [43]. However, in the study of Mora et al. [44], results were obtained that lower extremity fatigue during the free squat movement reduced plantar pressure. The results of the studies in the literature show differences regarding the changes in plantar pressure variables, which are thought to be due to the variability of the methods used. The fact that three different set configurations did not cause a difference in static foot plantar pressure variables suggested that these three different set combinations did not cause foot deformities and shape differences on the plantar surface of the foot. Therefore, results of the present study about FC_avg, FC_max, 95% CEA and COPPL can be an important reference point for the future research to compare the effects of different set methods on the plantar pressure variables when evaluating the training effect.

4.3 Effects of TS and CS configurations on the HS

In the present study, the BV_avg and BV_peak and BP_avg and BP_peak exhibited in half squat movement were significantly higher values in CS configurations than the TS configuration, indicating that the CS configurations are effective set configurations in resistance training to reduce fatigue and maintain mechanical performance (force, movement speed, and power output, etc.), as explained by Piqueras-Sanchiz et al. [18]. In another study [22], which supports the current study results, 6 set squats were applied as many as possible until they fell below the 90% BP_peak output. In the TS configuration, 2-min rest was made between sets, and in the CS configuration, 2 min rest was made between sets and 20 s rest after every two reps. The present study yielded similar results to those of previous studies, indicating that the CS configuration is an appropriate set configuration for augmenting the volume of velocity-based training. This approach involves the completion of sets when repetitions fall below the velocity or power threshold.

Tufano et al. [19] compared the effects between TS and 2 cluster sets (CS2 and CS4) configurations and found that CS configurations were more effective in terms of BV_avg, BV_peak, BP_avg, BP_peak than TS configuration. Jukic et al. [6] showed that 6 × 3 reps CS1 with 3 min rest between sets and 30 s rest between reps and 2 × 9 reps CS2 with 3 min rest between sets and 45 s rest between reps were more effective in reducing the overall decrease in repetition velocities compared to the 6 × 3 reps TS configuration without rest between reps. Therefore, it was suggested that both CS1 and CS2 configurations can be used to reduce fatigue. The present study results supported Jukic et al.’s [6] study in terms of the maintenance of neuromuscular fatigue. In the study of Wetmore et al. [20], it was determined that the CS configuration, which includes 3 min of rest between sets and 30 s between each rep in 3 × 5 reps of squats with 80% of 1RM, provides higher power output, speed, and force than the TS configuration with 3 min of rest between sets. In the study of García-Ramos et al. [21], bench press with a total of 30 reps with 5 min rest between sets was applied with five different set configurations (3 × 10 reps TS1, 6 × 5 reps TS2, 3 × 10 reps CS5 with 5 s rest between reps, 3 × 10 reps CS10 with 10 s rest between reps and 3 × 10 reps CS15 with 15 s rest between reps). A comparison of the first and last sets revealed a decrease in movement velocity in TS1, CS10 and CS15. Based on velocity loss, the set configurations are ranked as TS1 > CS5 > CS10 > TS2 > CS15. These results supported the use of TS2, CS10 and CS15 configurations for the maintenance of high mechanical outputs and showed that CS10 and CS15 configurations produced less metabolic stress than the TS2 configuration. Api et al. [7] determined that there was less decrease in mechanical performance in CS configurations even when the total rest interval was equal. Based on the studies [6, 7, 18, 19, 20, 21, 22] and the results of this study on BV and BP, the suggestion is more efficient to use a CS configuration with a high number of in-set rests.