
==== Front
Sci Rep
Sci Rep
Scientific Reports
2045-2322
Nature Publishing Group UK London

39266662
72234
10.1038/s41598-024-72234-0
Article
Sex differences in the adaptations in maximal strength and anaerobic power to upper body plyometric training
Lu Guotian 1
Duan Yimei duanyimei_0102@outlook.com

12
1 grid.412600.1 0000 0000 9479 9538 Institute of Physical Education, Sichuan Normal University, Chengdu, 610101 Sichuan China
2 https://ror.org/05580ht21 grid.443344.0 0000 0001 0492 8867 Institute of Sports Medicine and Health, Chengdu Sport University, Chengdu, 610041 Sichuan China
12 9 2024
12 9 2024
2024
14 213044 5 2024
4 9 2024
© The Author(s) 2024
2024
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This study aimed to compare the effects of a 6-week upper body plyometric training (UBPT) on maximal strength and anaerobic power performance of male and female subjects. Forty collegiate physically active male and female subjects participated in the study and were assigned to either UBPT group (M-UBPT, n = 10, F-UBPT, n = 10) or control group (M-CON, n = 10; F-CON, n = 10). The training groups performed 6 weeks of progressive overload UBPT three times per week using six exercises and were evaluated for upper-body anaerobic power and maximal strength, 3-kg medicine ball throw (MBT), push-up endurance, and reaction time at pre- and post-intervention. After the training intervention, the M-CON and F-CON groups did not show significant (p > 0.05) changes in the variables, while both the M-UBPT and F-UBPT groups demonstrated significant (p = 0.001) medium to very large improvements in their performance as follows: maximal strength (effect size [ES] = 0.55, 0.92), MBT (ES = 1.96, 0.89) peak power output (ES = 2.31, 1.52), mean power output (ES = 2.19, 1.11), push-up endurance (ES = 1.26, 0.70), and reaction time (ES =  − 2.16, − 1.56), respectively. Nevertheless, the male group experienced more significant improvements in the MBT (p = 0.001), peak (p = 0.001) and mean power output (p = 0.01), as well as reaction time (p = 0.01) compared to the female group when utilizing UBPT. In conclusion, it is imperative to take sex into account as a crucial factor when incorporating UBPT, particularly if the objective is to enhance anaerobic power output, muscular power, and reaction time.

Keywords

Plyometric training
Upper-body performance
Anaerobic power
Physical performance
Subject terms

Physiology
Metabolism
Sichuan Normal University Research Fund ProjectXJ20200163 Lu Guotian Sichuan Normal University Teaching Reform Project20220001XJG Lu Guotian issue-copyright-statement© Springer Nature Limited 2024
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pmcIntroduction

Plyometric training utilizes a repetitive sequence of movements, where each cycle includes a rapid deceleration of the body, immediately followed by a brief transition phase and a quick acceleration in the opposite direction1. The rapid integration of eccentric and concentric muscular activity engages the stretch–shortening cycle (SSC), which provides a physiological benefit as the muscular force generated during the concentric phase is enhanced by the preceding eccentric action2. The requirements of the SSC criterion task can influence the specific mechanisms supporting each SSC activity, which can be categorized as slow or fast3. Fast SSC is characterized by brief contraction times (< 200–300 ms) and minimal angular displacements (i.e., depth jump), while slow SSC involves longer contraction times (> 400 ms) and greater angular displacements (i.e., countermovement jump)4,5. The engagement of the SSC during both rapid and slow transitions from eccentric to concentric movements appears to be beneficial in improving the lower-body physical performance of athletes and non-athletes1–5. Indeed, lower-body plyometric training is an effective way to improve physical performance (i.e., strength, power and sprinting speed) in the general population and overall health, including enhanced bone mineral density and injury prevention6; however, recent studies have shown that incorporating upper-body plyometric training (UBPT) can also be beneficial for enhancing upper-body physical performance7,8.

To design an optimal training program, the consideration of several training variables, including rest intervals between sets and training sessions, intensity, volume loads, type of exercise, and training duration, are crucial3,9. However, the importance of sex differences in designing suitable UBPT programs has been overlooked. It is well-established that females possess inherent advantages in endurance situations, characterized by a superior aerobic metabolism, reduced fatigue, and quicker recovery compared to male subjects10. Although males typically have a larger body size, which enables them to generate greater force and achieve higher speeds during intense performances, several factors contribute to these differences between sexes, including variations in muscle mass, substrate utilization, and muscle morphology10,11. However, there is currently no evidence comparing the response of male and female subjects when UBPT was employed.

Considering the lack of previous studies that have analyzed the independent influence of sex on the adaptations resulting from long-term UBPT (i.e., a duration of 6 weeks), it would be a suitable area for investigation. In a previous study by Ramirez-Campillo et al.12, it was found that sex did not have an impact on physical fitness attributes in soccer players after lower-body plyometric training. However, when comparing male and female subjects, the results of upper-body physical fitness attributes could be influenced by the amount of muscle mass involved during UBPT13. Typically, males have a higher level of muscularity in their upper-body compared to females, which could potentially lead to greater adaptive responses following UBPT13. However, this is a speculative observation and requires further investigation in this context.

Furthermore, the principle of subject differences was missed in the studies using upper extremity plyometric training. In fact, previous research investigating the impact of UBPT did not determine subject responses to training7,8,14. When selecting a training program for enhancing physical performance, it is crucial to consider the subject responses to training, as subjects may exhibit varying responses. Indeed, the prior studies have focused on investigating the impact of UBPT on performance typically reported overall group response, neglecting to account for the subject differences in response to training. Consequently, it is essential to carefully consider the optimization of subject responses to UBPT.

There is a lack of research on examining sex differences in plyometric training using upper-body7, and no studies are available to examine subject responses to training for clarifying sex differences. Therefore, the primary aim of the current study was to examine the effects of a 6-week UBPT on upper-body anaerobic power and maximal strength, 3-kg medicine ball throw (MBT), push-up endurance, and reaction time in physical active male and female. The secondary aim was to identify sex differences in adaptations by analyzing the inter-subject variability of male and female populations.

Methods

Study population and sample size

This research employed collegiate physically active male and female who were familiar with upper-and lower-body plyometric training. In order to calculate the appropriate sample size for this study, the G*Power software (Version 3.1.9.2, University of Kiel, Germany) was utilized, taking into account an effect size of 0.8, a power of 0.8, and a p-value of 0.05 based on a previous study that examined the effects of UBPT on the physical performance8. The analysis indicated that a sample size of N = 8 would be appropriate for identifying significant changes in physical fitness following the introduction of UBPT. Nevertheless, to address the possibility of subject dropout during data collection, the sample size was later increased to 10 subjects per group.

Subjects

Forty collegiate physically active male and female subjects participated in the study and were randomly assigned to either UBPT or control groups (Table 1). The distribution of groups was determined through a computer-generated random number, resulting in an unpredictable outcome for both researchers and subjects. Subsequently, subjects were randomly assigned to one of four groups. The randomization process was executed using R software (version 2.14, Foundation for Statistical Computing). All subjects were familiar with upper-and lower-body plyometric exercises and employed these types of exercises in their weekly training routines, but they had not engaged in planned plyometric training sessions for the past 3 months before their inclusion in the study. In order to be included in the study, the subjects had to meet certain requirements. These requirements included not using any ergogenic aids, and not having any lower or upper-body injuries that prevented them from performing plyometric training. Also, a comprehensive evaluation of subjects’ injury history was conducted by a sport-medicine physician. Prior to the initiation of the study, all subjects were thoroughly informed of the research procedures, requirements, benefits, and risks, and they provided written informed consent. The study design was approved by the Ethics Committee of the Sichuan Normal University (NO. 202400187) and was conducted according to the ethical guidelines outlined in the Declaration of Helsinki.Table 1 Descriptive data of the male upper-body plyometric training (M-UBPT, n = 10), male control (M-CON, n = 10), female upper-body plyometric training (F-UBPT, n = 10), and female control (F-CON, n = 10) groups.

	M-UBPT	M-CON	F-UBPT	F-CON	
Age (y)	21.2 ± 1.4	22.5 ± 2.1	21.6 ± 1.2	21.8 ± 1.9	
Height (cm)	176.1 ± 5.5*	175.6 ± 4.6*	164.6 ± 4.7	163.6 ± 4.9	
Body mass (kg)	75.5 ± 4.1*	77.5 ± 3.8*	66.5 ± 3.6	65.7 ± 4.8	
*denotes significant differences in height and body mass between male and female groups as analyzed by t-test (p < 0.05).

Experimental design

A parallel, matched-group, and longitudinal (pre-test/post-test) study design was utilized over 8 weeks, including 1 week of pre-test, 6 weeks of UBPT, and 1 week of post-test to determine inter-subject variability to adaptive responses with aiming to identify sex differences. Prior to the baseline testing, a laboratory orientation was carried out to ensure that all subjects were familiar with the testing and training procedures, as well as the objectives of the study. The subjects were recruited for two separate sessions. On day 1, they underwent tests for the 3-kg medicine ball throw (MBT), push-up endurance, and upper-body anaerobic power. On day 2, they were assessed for reaction time (RT), and maximal strength. There was a 10-min rest period between each test and a 72-h interval between the two testing sessions. All tests were conducted in the afternoon (i.e., 4–6 P.M) and took place in an indoor basketball wooden court for physical performance and a laboratory environment for other variables to ensure control over any variations. A trained researcher oversaw each testing session to confirm the accurate completion of all tests, with specialist strength and conditioning coaches conducting each test to maintain consistency throughout the testing sessions. Following the completion of the pre-test measurements, a period of 6 weeks of UBPT was initiated for the subjects. Subsequently, 72 h after the final training session, a post-test was conducted with identical conditions and testing order.

Procedures

Prior to the testing days, all subjects were given instructions to follow specific guidelines, including a) getting 8 h of sleep, b) consuming the appropriate amount of carbohydrates (i.e., 65% of daily caloric intake) as prescribed for each subject, and c) not using any power booster (i.e., caffeine) both the pre and post-tests15,16, which was confirmed by a personal interview before measurements were done. In preparation for the tests, all subjects had to complete a 15-min general warm-up routine, including a 5-min running, followed by a 5-min upper-body stretching session, concluding with 5 min of ballistic exercises for the upper body. All measurements were taken within a temperature range of 27–29 °C, both on the gym and in the laboratory environment.

Anthropometric measurements

The total height measurement was conducted utilizing a stadiometer (± 0.1 cm, SECA, Germany), while the body mass was determined using an electronic scale (± 0.1 kg, BEURER, Germany).

MBT test

A seated MBT was employed to assess the upper-body muscular power. Subjects seated on the chair and held a 3-kg medicine ball with both hands in front of their bodies, keeping their arms 90° flexion. They were instructed to throw the ball to achieve the greatest distance possible forcefully. A backward and forward countermovement was not permitted throughout the throwing motion, and the best score from 3 trials with a 30-s rest period between each trial was chosen for analysis.

Push-up endurance test

Upper-body muscular endurance performance is measured using the push-up test, which involves a trial focused on achieving maximum repetitions. Under the examiner’s guidance, each subject was instructed to assume the push-up position. The examiner emphasized the correct hand placement under the shoulders, the importance of keeping the arms straight, stretching out the fingers, and ensuring the legs were together and straight with the toes tucked downward. To successfully perform a push-up, subjects were required to lower their bodies by bending their elbows to a 90° angle and straightening their arms while maintaining a straight line with their back and legs throughout the movement. The objective was to complete as many push-ups as possible. The evaluation would be finalized if a subject discontinued or paused, was unsuccessful in maintaining the correct body position, did not fully extend their arms, or did not accomplish a 90° bend at the elbow during a minimum of two push-ups14.

Upper-body anaerobic power test

Subjects underwent the 30-s Wingate anaerobic power test once to assess their upper-body mean power output (MPO) and peak power output (PPO). In this study, subjects were required to exert maximum effort on a mechanically braked arm ergometer (891E; Monark, Vansbro, Sweden). The resistance applied was equivalent to 0.050 and 0.040 kg per kilogram of body mass for male and female subjects, respectively17–20. The subjects were directed to initiate the cranking motion as quickly as possible, exerting force against the inertial resistance of the ergometer. Once this was done, the appropriate load was manually incorporated. Verbal encouragement motivated subjects to sustain a fast-cranking pace throughout the test. The PPO and MPO were assigned to represent the maximum power reached the 5-s mark and the average power sustained throughout the test, respectively17–20.

Reaction time test

Reaction time (RT) was measured using an electronic timing system (± 1/1000 sensitivity, Newtest, Oulu, Finland). This system consisted of a digital display, a light, a button, and the procedure described in detail previously. Briefly, each subject was seated in a calm environment with his/her resting arm on the table. The second index finger of the testing side was positioned 1 cm away from the device’s button. The subjects were then instructed to press the button upon the appearance of a visual stimulus assigned randomly by their dominant hand. The mean score of the last 5 tests from 10 repetitions was recorded for further analysis14.

Upper-body maximal strength test

The bench press exercise assessed the upper body’s maximum strength, following the guidelines established by Kraemer and Fry21. Subjects were instructed to lower the bar until it made contact with their chest and then raise it to a fully extended elbow position. Any attempts that did not meet the specified technique criteria were excluded. Following a standardized warm-up, subjects completed 3–5 sets of weight lifts with a 2-min rest period in between until they reached their one repetition maximum (1RM). The heaviest weight successfully lifted by each subject while maintaining proper exercise technique was considered his/her 1RM.

UBPT program

All subjects included in the study maintained an active physical status by participating in weekly aerobic and full-body resistance training sessions lasting 150 min. The M-UBPT and F-UBPT groups engaged in 3 days per week plyometric training (on Mondays, Wednesdays, and Fridays) for 6 weeks. In contrast, the control groups did not partake in any organized training program and instead continued with their regular physical routines. Each training session lasted for approximately 60–70 min and took place in the afternoon, from 4:00 to 6:00 P.M. Prior to the training, a 15-min warm-up was conducted, which included 5 min of light running, 5 min of upper-body stretching, and 5 min of upper-body ballistic and elastic band exercises. The UBPT program was designed to follow a progressive overload approach, incorporating multiple sets and exercises as per the guidelines provided by Chu22 and Garcia-Carrillo et al.7 (Table 2). All subjects maintained an active physical status and engaged in weekly aerobic and full-body resistance training sessions lasting approximately 150 min. The M-UBPT and F-UBPT groups incorporated plyometric training into their routine, along with once-weekly resistance training sessions lasting 70–90 min at moderate intensity, and aerobic activities lasting 60–70 min with low to moderate intensity. In contrast, subjects in the control groups (both M-CON and F-CON) were instructed to continue their daily physical activities similar to those in the training groups but did not follow a structured training program. The adherence of the control groups to the study protocol was confirmed through weekly phone interviews, and a personal interview was conducted before any post-test measurements. Under the guidance of an expert strength and conditioning coach, the entire training program was closely monitored to ensure that the subjects followed appropriate training methods and exerted maximum effort in each trial. To assess the training load of the UBPT, the participants’ rating of perceived exertion (RPE) was measured using a scale of 0–10, 10 min after the completion of exercise sessions23. Furthermore, the training load was determined by multiplying the sRPE with the duration of training in minutes24.Table 2 Six-week upper-body plyometric training program.

Exercises*	Sets × Repetitions	
Week 1	Week 2	Week 3	Week 4	Week 5	Week 6	
Chest pass with medicine ball**	3 × 8	3 × 9	3 × 10	3 × 9	3 × 10	3 × 11	
Overhead throw with medicine ball	3 × 8	3 × 9	3 × 10	3 × 9	3 × 10	3 × 11	
Plyo push-up with knee ground touch	3 × 8	3 × 9	3 × 10	3 × 9	3 × 10	3 × 11	
Medicine ball slams	3 × 8	3 × 9	3 × 10	3 × 9	3 × 10	3 × 11	
Lying medicine ball drop	3 × 8	3 × 9	3 × 10	3 × 9	3 × 10	3 × 11	
Seated throw circuit	3 × 8	3 × 9	3 × 10	3 × 9	3 × 10	3 × 11	
Total trials in each session	144	162	180	162	180	198	
Total trials in each week	432	486	540	486	540	594	
*30-s and 120-s rest between sets and exercises, respectively.** 3-kg medicine ball.

Statistical analysis

The mean ± SD was used to present the data. The normality of both pre-and post-values for the dependent variables was assessed using the Shapiro–Wilk Normality test. A repeated-measures ANOVA (4 [group] × 2 [time]) was conducted to identify significant differences between the four groups for each tested variable. The effect size (ES), determined by Hedges’g, was categorized as trivial (< 0.20), small (0.20–0.50), medium (0.50–0.80), large (0.80–1.30), or very large (> 1.30). The 95% confidence interval (CI) was also reported24. The significance level was set at 0.05. The coefficient of variation (CV) was calculated to assess inter-subject variability over time. The percent changes (∆ %) from pre-training to post-training were calculated for each variable, and these changes’ mean (SD) was determined. The CV (ratio of SD to the mean) of percent changes was then calculated for each variable. Additionally, subject residuals were computed as the square root of the squared difference between subject and mean values for each tested variable. Finally, the impact of interventions on inter-subject variability in variables was evaluated by comparing between-group mean residuals for each variable. The t-test was used to determine the differences between the training and control groups, as well as sex differences in the anthropometric measures and variable measured.

Results

Concerning physical characteristics, the male group displayed a notable advantage in height and body mass compared to the female group (p < 0.05). Moreover, the performance tests demonstrated significantly superior for male groups than the female groups at both prior to and following the training period (p < 0.05). Throughout the study, every subject exhibited absolute compliance, leading to a remarkable achievement of attaining a success rate of 100%, which determined for each subject by presence/absence sheets that checked in each training session. Additionally, there were no documented incidents of injuries related to the training and testing interventions that checked through the study duration by reporting the rate of injury appearance by subjects. The control groups (M-CON and F-CON) did not show significant (p > 0.05) changes in their performance measures including MBT, MPO, PPO, push-up, strength and RT at post-training. In addition, after the training period both the training groups indicated significant differences compared with their control groups in all variable measured (p = 0.001).

Significant (p = 0.001) improvements were observed in the variable measured for both the M-UBPT and F-UBPT groups after 6 weeks of training, with ESs ranging from medium to very large (Table 3). In addition, there was a significant group by time interaction in MBT (F = 43.16, p = 0.001), PPO (F = 38.12, p = 0.001), MPO (F = 19.61, p = 0.01) and RT (F = 23.77, p = 0.013), indicating greater adaptations for the M-UBPT than the F-UBPT following the 6-week training intervention.Table 3 Changes in the variables from pre- to post-training (mean ± SD).

Variables	Pre-test	Post-test	t-test
p value*	Mean difference	ES with 95% CI	Description	
MBT (cm)	
M-UBPT	610.5 ± 34.6	679.5 ± 32.4	0.001	69	1.96 (0.89 to 3.03)	Very large	
M-CON	598.2 ± 28.3	601.8 ± 30.6	–	–	–	–	
F-UBPT	463.1 ± 34.4	495.1 ± 34.8	0.001	32	0.89 (− 0.03 to 1.80)	Large	
F-CON	451.6 ± 33.7	452.3 ± 28.4	–	–	–	–	
PPO (w)	
M-UBPT	531.2 ± 33.9	613.2 ± 34.1	0.001	82	2.31 (1.18 to 3.44)	Very large	
M-CON	511.7 ± 35.6	515.2 ± 38.4	–	–	–	–	
F-UBPT	348.9 ± 24.9	388.1 ± 24.6	0.001	39.2	1.52 (0.52 to 2.51)	Very large	
F-CON	351.5 ± 23.8	353.8 ± 24.5	–	–	–	–	
MPO (w)	
M-UBPT	381.2 ± 25.9	440.6 ± 26.1	0.001	59.4	2.19 (1.08 to 3.30)	Very large	
M-CON	366.6 ± 22.7	368.4 ± 23.9	–	–	–	–	
F-UBPT	249.8 ± 24.7	277.3 ± 22.6	0.001	27.5	1.11 (0.17 to 2.05)	Large	
F-CON	238.2 ± 21.3	239.1 ± 21.7	–	–	–	–	
Push-up (reps)	
M-UBPT	39.4 ± 3.3	43.6 ± 3.1	0.001	4.2	1.26 (0.30 to 2.22)	Large	
M-CON	37.5 ± 4.1	37.6 ± 4.4	–	–	–	–	
F-UBPT	30.4 ± 4.2	33.6 ± 4.5	0.001	3.2	0.70 (− .20 to 1.61)	Medium	
F-CON	29.5 ± 3.8	29.6 ± 3.6	–	–	–	–	
Strength (kg)	
M-UBPT	45.7 ± 7.7	50.2 ± 8.1	0.001	4.5	0.55 (− 0.35 to 1.44)	Medium	
M-CON	43.8 ± 9.6	42.7 ± 10.5	–	–	–	–	
F-UBPT	31.2 ± 3.4	34.5 ± 3.5	0.001	3.3	0.92 (− 0.01 to 1.84)	Large	
F-CON	32.9 ± 4.8	33.6 ± 5.1	–	–	–	–	
RT (ms)	
M-UBPT	249.5 ± 10.7	221.5 ± 13.9	0.001	− 28	− 2.16 (− 1.06 to − 3.27)	Very large	
M-CON	255.1 ± 13.6	253.6 ± 15.7	–	–	–	–	
F-UBPT	279.5 ± 10.8	258.9 ± 13.5	0.001	− 20.6	− 1.56 (− 0.56 to 2.57)	Very large	
F-CON	284.6 ± 11.3	279.3 ± 11.6	–	–	–	–	
*denotes pre to post-intervention t-test p values indicating significant changes following the training program. MBT, medicine ball throw; PPO, peak power output; MPO, mean power output; RT, reaction time.

Comparative analyses of group changes indicated M-UBPT group resulted in a significantly (p < 0.01) greater change in MBT (11.3 ± 1.8% versus 6.9 ± 1.8%), PPO (15.4 ± 1.7% versus 11.3 ± 2.3%), MPO (15.6 ± 4.1% versus 11.6 ± 4.5%), and RT (− 11.2 ± − 3.9% versus − 7.4 ± − 4.0%) than F-UBPT group. However, the groups’ changes in push-ups, and muscular strength were the same (p > 0.05). Also, analyzing residuals in adaptive changes revealed similar inter-subject variability in response to training (p > 0.05) (Figs. 1, 2, 3). However, the M-UBPT indicated a lower CV than the F-UBPT (Fig. 4).Fig. 1 Percent change and residuals in percent change in the MBT (A), PPO (B), and MPO (C) for the M-UBPT and F-UBPT. ** Indicates significant differences compared to F-UBPT using t-test (p ≤ 0.05).

Fig. 2 Percent change and residuals in percent change in the push-up (A), and strength (B) for the M-UBPT and F-UBPT.

Fig. 3 Percent change and residuals in percent change in the RT for the M-UBPT and F-UBPT. ** Indicates significant differences compared to F-UBPT using t-test (p ≤ 0.05).

Fig. 4 Inter-subject variations (CV) of performance measures for the M-UBPT and F-UBPT groups.

The training load for the experimental groups are presented in Table 4. Although the F-UBPT group reported lower sRPE and training loads than the M-UBPT, these differences were not statistically significant (p > 0.05).Table 4 Training load in the experimental groups.

Groups	sRPE (scale)	Training time (min)	Training load*	
M-UBPT	8.2 ± 0.8	30	4428	
F-UBPT	7.1 ± 0.7	30	3834	
sRPE, sessions rating of perceived exertion. * Training load = RPE × training time.

Discussion

Previous research has been conducted to assess the efficacy of UBPT methods in enhancing the physical performance measures in male25–27 and female8,14,28,29, demonstrating that PT for the upper body is a suitable approach for improving both physical and sport-related performance. However, it remains unclear whether this type of training has comparable effects on both males and females in maximizing anaerobic capacities, and physical performance. Hence, the objective of the present study was to examine of UBPT on upper-body anaerobic power and maximal strength, 3-kg medicine ball throw (MBT), push-up endurance, and reaction time in physical active male and female subjects, focusing on identifying any sex differences in adaptations through the analysis of inter-subject variability. The results indicated that UBPT is highly effective in inducing adaptive responses in physical performance. Nevertheless, the male group exhibited greater adaptations in anaerobic capacity, MBT, and RT while demonstrating similar gains in other variables compared to the female group.

Significant improvements in MBT, PPO, and MPO were observed in both the M-UBPT and F-UBPT groups after the 6-week training. In addition, the training groups indicated meaningful effects than the control groups at post-intervention. However, it was noted that the M-UBPT group displayed greater adaptive responses compared to the F-UBPT group. These findings are consistent with previous research studies8,26,28, highlighting the positive transfer of UBPT to increase muscular power and anaerobic power output parameters. The observed enhancements in muscular power measured by MBT for both groups can be attributed to the enhancement of the mechanical properties of the muscle–tendon system, improved muscle coordination, increased firing rate of alpha motor neurons, and overall neuromuscular adaptations in the upper body3,7,14. The alterations observed in the PPO and MPO may be attributed to adjustments in the recruitment or activation of motor units, an increase in muscle phosphocreatine concentration, and a significant rise in type IIa fibers, alongside a decline in type I fibers16,26.

Although it has been previously reported that the male subject exhibits a higher level of trainability compared to female subjects after training13, other research reported similar power adaptations between male and female after lower-body PT12. Concerning sex differences from the UBPT, this was the first study, and an explanation for these findings could be complicated. Greater gains in MBT, PPO, and MPO for the male than the female could be due to differences between sexes in power-related parameters, including muscle fiber types, muscle quality, or glycolytic enzymatic activities13,30. Male subjects tend to have greater muscle thickness than females, particularly in the trapezius and pectoral muscles31,32. This can increase the workload per muscle fiber during UBPT, leading to enhanced muscle activation and firing rate and improving power performance3. Moreover, it has been suggested that the length of muscle fascicles is pivotal in determining the muscle’s maximum contraction velocity and the range of active force production31. By incorporating a larger number of sarcomeres in series, longer fascicles allow for a higher contraction velocity32. This characteristic can be particularly beneficial during plyometric training exercises. Consequently, men may experience greater muscular power and anaerobic power output parameters compared to women when engaging in such training protocols.

The training groups showed significant changes in muscular endurance (specifically push-ups) and strength compared to their pre-training values. The magnitude of change did not differ significantly between the two groups. Previous studies have reported improvements in muscle endurance and strength following lower-body PT could be due to increased motor neuron excitability, higher firing frequency of motor units, enhanced efferent motor drive33, and improved buffering capacity34–37. These mechanisms also play a role in improving push-up performance and maximal strength for both the male and female UBPT groups. Both sexes experienced comparable training benefits through PT, indicating that the adaptive responses to UBPT are similar between male and female.

An interesting finding of this study was the similar adaptive responses in maximal strength for both sexes, which is in line with numerous studies that have examined the effects of different training types on strength gains in both males and females and have found similar patterns of improvement when relative changes are considered38,39. However, it should be noted that while the F-UBPT group showed similar or slightly greater gains in strength performance, there were more subject variations in response to training within the female group compared to the male group. This aspect has been overlooked in previous studies that have compared male and female to determine sex differences in training response38,39. The results from UBPT indicate that the male group exhibited greater consistency in adaptations compared to the female group, suggesting that males may have a higher level of trainability when UBPT is utilized.

Significant improvements in RT was observed in both the M-UBPT and F-UBPT groups after the 6-week training and in comparison to control groups. However, it was noted that the M-UBPT group displayed greater adaptive responses compared to the F-UBPT group in the RT. The current evidence makes it relatively difficult to interpret our findings regarding the impact of UBPT on RT. However, a study conducted by Turgut et al.14 demonstrated a positive effect of upper-body RT achieved through 6 weeks of ballistic exercises using elastic bands. The motor control system’s organization is intricately connected to their capacity to respond to visual stimuli in sports40. This capacity relies on the information provided by the perceptual system40. Since PT is a means to enhance the sensory-motor system41, an improvement in RT can be expected. Notably, UBPT leads to a more significant improvement in visual RTs for males compared to females, highlighting the impact of sex on adaptation via differences in cognitive tasks and better contractile ability of the male than female, leading to more gains in RT.

Conclusion

Incorporating short-duration UBPT yielded enhanced physical performance and improved anaerobic power parameters for both male and female subjects; however, the utilization of UBPT resulted in greater gains for the male group in the MBT, PPO, MPO, and RT compared to the female group. From a practical perspective, it is crucial to consider sex as a significant factor when implementing UBPT, especially when the aim is to enhance parameters related to anaerobic power output, muscular power, and reaction time.

Acknowledgements

The authors express their gratitude to the participants for their valuable contribution and cooperation and to the Human Performance Laboratory team for their unwavering technical support. This study was supported by the Sichuan Normal University Research Fund Project (XJ20200163) and the Sichuan Normal University Teaching Reform Project (20220001XJG).

Author contributions

G.L. and Y.D. contributed equally to every aspect of this experiment, including conceptualization, study design, supervision, data collection, statistical analysis, interpretation, writing, and reviewing. All authors reviewed and endorsed the final version of the manuscript.

Data availability

The datasets used and analyzed during the current study are available from the corresponding author (Y.D) upon reasonable request.

Competing interests

The authors declare no competing interests.

Publisher's note

Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.
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