Introduction

Strength is a fundamental quality of the human body for sports, essential for developing other physical attributes and improving sports performance and competitive outcomes [1]. Many researchers are dedicated to discovering advanced training methods to improve athletes’ muscle strength and performance [2,3]. Badminton is a multidirectional explosiveness-dependent sport [4], and the key to success lies in showing intense rhythmic movements, which include shuffling, jumping, twisting, stretching, and striking combined with a superior reactive ability [5]. A recent study quantifying muscle synergies during high-velocity badminton techniques revealed that performance is dependent on highly specialized neuromuscular coordination patterns to achieve maximal movement velocity [6]. This complex neuromuscular control mechanism indicates that explosive power in badminton stems not only from muscle strength and power output, but also requires the result of efficient and coordinated muscle recruitment. However, these qualities possess distinct physiological adaptive demands, making their simultaneous development within a training program a complex task for practitioners.

The Post-activation performance enhancement (PAPE) is a physiological phenomenon characterized by a transient increase in muscular performance following a conditioning activity, serving as the foundational mechanism for a variety of contemporary training strategies [7]. One such strategy is Complex Training (CT), which alternates high-intensity strength exercises with biomechanically similar plyometric or ballistic movements within a single session [8–10]. Complex training takes advantage of the PAPE mechanism to efficiently and simultaneously develop strength and explosive power in a single training session, meeting the training needs of practitioners. A more structured variant is the French Contrast Method Training (FCMT). Developed by French track and field coach Gilles Cometti and later promoted by Dietz. The FCMT employs a precise sequence of four exercises (large load → bodyweight jumps → light load → assisted jumps) with varying loads to maximize PAPE, thereby enhancing short-term explosive performance (e.g., in jumping and sprinting) and bringing about a significant anaerobic challenge that improves physiological endurance [11]. It is theorized that this approach may also foster long-term adaptations for more efficient power production [11].

Recent updates to badminton rules, techniques, and tactics have introduced a new level of unpredictability to match outcomes, challenging players to adapt to their bodies in new ways. Chunlei Li’s analysis highlights the critical role of short bursts of explosive power in matches where the ratio of net playing time to intervals is approximately 1:2, with rounds lasting less than 10 seconds accounting for 80% of matches [12]. However, with the shift in modern tactics to longer rounds of more than 10 seconds, with short breaks between scores (typically 27–30 seconds), the average length of the game has become longer, implying that sustaining explosive endurance is important to winning the game [12,13]. During long matches, players must demonstrate the explosiveness and endurance to handle frequent starts, stops, and quick movements in limited space. This requires strong muscle contractions, as well as effective utilization of the stretch-shortening cycle. Previous studies have shown that combining resistance training and plyometric training can effectively enhance the agility and reactive strength of athletes [14]. However, the impact of FMCT on the agility and reactive strength of athletes remains unclear.

Badminton players traditionally prioritize technical and tactical training over physical conditioning before matches, presenting a challenge in enhancing physical fitness within a constrained timeframe. Evidence indicates that CT’s appeal among coaches stems primarily from its time efficiency, as this method can yield comparable improvements in athletic performance to traditional strength and power training, but in a more time-efficient manner [15,16]. Several studies have explored the short- or long-term effects of FCMT on adult players on various outcome indicator [17–22]; however, there is limited research on the long-term effects of FCMT on adolescent badminton players. In addition, few studies have compared FCMT and CT with each other and few studies have explored the adaptation period of athletes to FCMT. Therefore, this study therefore aimed to determine if 8 weeks of French Contrast Method Training (FCMT) is more effective than Complex Training (CT) at improving lower limb power and its endurance in junior badminton players, while also evaluating the adaptive responses to both training modalities.

Methods

Results

As shown in Fig 1, no adverse reactions due to injury or early study withdrawal were reported by any subject during the 8-week study period. Furthermore, based on our observations, all subjects scored 3 points in the overhead squat test. Ultimately, data from 20 subjects (10 in the FCMT group and 10 in the CT group) were included in the statistical analysis. At baseline, there were no significant differences in descriptive variables or exercise parameters between the FCMT and CT groups (Tables 2 and 3).

Discussion

Explosive strength is influenced by multiple factors [49,50], so a single test to assess the effect of explosive strength enhancement has limitations, and the present study used a multidimensional explosive strength test to accurately analyze the mechanism of action of the two training methods. The results showed that the French contrast method training (FCMT) could significantly improve the lower limb explosive strength and explosive endurance of adolescent athletes, while Complex Training (CT) could significantly improve the lower limb explosive strength but not the explosive endurance. In the overall dimension, FCMT significantly outperformed CT in terms of explosive strength enhancement; in the local dimension, FCMT outperformed CT in terms of reactive strength, agility, and SSC utilization, while there was no significant difference between the two in terms of speed strength and maximal strength enhancement (Fig 4). Therefore, the explosive power improvement advantage of FCMT over CT mainly originated from the enhancement of reactive power, agility ability and SSC utilization ability.

The superior gains in reactive strength, agility, and stretch–shortening cycle (SSC) efficiency observed with French Contrast Method Training (FCMT) relative to Complex Training (CT) are plausibly attributable to differences in session organization and post-activation performance enhancement (PAPE) strategies. Whereas CT employs two independent contrast pairs, FCMT implements a sequential four-exercise progression that exposes the neuromuscular system to stepwise reductions in external load within each cycle. This configuration likely provides a broader stimulus across the force–velocity spectrum than paired contrasts. Conceptually, FCMT’s multi-load sequence also accords with the contemporary joint-by-joint paradigm, emphasizing inter-joint coordination and kinetic-chain force distribution—mechanisms relevant to movement efficiency and injury-risk management in multidirectional sports such as badminton [51]. From a risk–benefit standpoint, FCMT therefore appears theoretically well-suited for pre-competition programming. Additionally, the progressive load reduction in FCMT helps prevent fatigue accumulation from exceeding the enhancement effects of PAPE [52], thereby preserving neuromuscular recruitment capacity. This interpretation aligns with our fatigue monitoring, which showed lower post-session fatigue in FCMT compared with CT. With respect to high-load activation, FCMT’s use of isometric contractions is consistent with evidence that isometrics elicit robust PAPE responses [26–29], and may enhance the rate of force development (RFD)—a determinant associated with lower-limb explosive strength, reactive strength, and eccentric utilization rate [53–55]. Critically, we observed that the FCMT group demonstrated significantly greater improvements in these specific performance metrics compared to the CT group. Previous studies have demonstrated that isometric preactivation enhances subsequent peak force and explosive power output [56], providing additional supporting evidence despite being indirect. Finally, the present explosive-strength gains are congruent with reports of FCMT-related improvements in lower-body power among adult athletes across multiple sports [17–22]. These mechanistic interpretations are hypothesis-consistent rather than causal; studies incorporating neuromuscular measures (e.g., EMG timing, RFD profiling) are warranted to directly test these pathways.

In addition, differences in PAPE activation methods result in differences in the level of stimulation of the neuromuscular system within the entire training unit may be a plausible reason for the differences in SSC utilization gains between the two groups. It has been shown that lower extremity explosive strength gains are closely related to the utilization of elastic potential energy in the muscle and the activation of the muscle stretch reflex [49], and that the neuromuscular response varies with the level of fatigue [57]. Studies by C. Nichol et al. [58] have demonstrated that high-intensity anaerobic glycolytic exercise immediately attenuates the stretch reflex as a result of metabolic changes, thus decreasing sensitivity of the neural reflexes. In the high-load activation phase, CT employed the back squat exercise, while FCMT utilized the isometric back squat. The perceived exertion associated with the dynamic back squat in CT was reportedly greater than that produced by the isometric activation method in FCMT [59]. Relevant studies indicate that the onset of fatigue disrupts the functioning of the autonomic nervous system [60]. However, due to the accumulation of metabolites produced by fatigue caused an increase in the excitability of the Schwann cells, which in turn inhibited the vertebral alpha motoneurons from emitting nerve impulses, thereby reducing subsequent skeletal muscle power output [61]. In addition, the stabilizing muscles are subjected to greater moments of force during weighted squats with changes in joint angles (e.g., erector spinae), whereas the forces on the stabilizing muscles during isometric squats are constant and relatively small during exercise. Additionally, in the timing of training components, the FCMT maximizes the effects of PAP and PAPE by controlling decreasing loads to reduce fatigue buildup between cycles and achieve optimal exercise performance. Compared to CT, FCMT was likely more effective in activating the neuromuscular system and reducing fatigue buildup during training components such as the isometric back squat, back squat jump, and band-assisted jump. Coincidentally, the perceived exertion results of this study showed that the CT group consistently had higher levels of perceived exertion than the FCMT group, a finding that also indirectly confirms the above observations.

The results of the present study highlight the benefits of the FCMT in enhancing agility, and while this advantage may be attributed to enhanced explosive power or improved stretch-shortening cycle (SSC) capacity, another compelling reason may be due to the increased neuromuscular efficiency and coordination of the FCMT. Previous research has demonstrated that gains in athletes’ agility capabilities may be attributed to enhanced neuromuscular efficiency and more effective utilization of the stretch-shortening cycle [62]. This mechanism is consistent with that proposed in this study. In addition, prior research has shown that there is a synergy between the components of the FCMT that seamlessly transmits force to activities with similar biomechanical requirements, especially those that require the generation of powerful thrusts from the hips and thighs [20]. Additionally, the advantages of FCMT for neuromuscular efficiency and coordination enhancement provide a more economical energy environment for explosive endurance gains, which is consistent with Cal Dietz et al. who suggest that FCMT can maintain greater power output over a longer period than CT, and provides a greater stimulatory effect to the body, with long-term adaptations leading to gains in speed endurance more significant [11].

This study utilized an uncommon and innovative assessment method to evaluate changes in subjects’ explosive endurance. Subjects were assessed for the velocity dispersion, i.e., the standard deviation of the velocity of the 15-repetition weighted squat, at a weight of 30% 1RM (purpose: explosive power production is more favorable at this load [63]. This innovative assessment method was chosen considering that the weighted squat is consistent in its movement pattern with the movements of the two training components. The results of the present study demonstrated the advantage of the FCMT in terms of an increase in explosive endurance, a result that is consistent with the results of two previous studies. Noufal K V et al. [20] found that the FCMT significantly improved anaerobic strength capacity in field hockey players by performing the FCMT on 15 field hockey players over 12 weeks. Chang et al. [64] performed a randomized controlled trial on 24 college students, and explored the effects of 8 weeks of high-intensity strength training (similar to the training structure of FCMT) and resistance training on athletic performance, and one of the results showed that this high-intensity strength training produced better improvements in mean anaerobic power compared to traditional resistance training, which is consistent with the findings of the present study. It is also worth considering that the adaptation period for CT was approximately 3 weeks compared to 1 month for FCMT, so athletes may have adapted to CT earlier than to FCMT, and the training effect of CT seems to be more dependent on the accumulation of load intensity. However, premature adaptation to CT in the CT group during the 8-week training intervention may also have reduced the degree of stimulation in subsequent training, leading to differences in explosive endurance gains between the two groups.

While the FCMT demonstrated clear superiority in metrics involving the explosive power and its endurance, it is noteworthy that both training protocols were equally effective in enhancing maximum strength (1RM squat), speed-strength qualities as measured by the Squat Jump (SJ), and sprinting acceleration as measured by the 10-meter sprint (T-10m). The absence of statistically significant between-group differences in these outcomes (p > 0.05 for 1RM, SJ, and T-10m metrics, Table 6) indicates that the foundational capacities for generating high levels of concentric force and initial acceleration were developed to a similar extent by both CT and FCMT. This finding underscores that the high-load component inherent to both protocols, the back squat in CT and the isometric back squat in FCMT, provided a sufficient stimulus for eliciting comparable neuromuscular and structural adaptations related to maximal force production. Consequently, for coaches whose primary aim in a training cycle is to build a solid strength base, improve concentric power, or enhance short-distance sprint performance, both CT and FCMT appear to be viable and effective strategies. Taken together, FCMT’s distinct advantage does not lie in superior development of primary concentric strength or linear sprint velocity, but rather in enhancing EUR and reactive strength, thereby optimizing the transfer of strength to subsequent reactive, explosive and its endurance-oriented tasks. Notably, all participants were elite adolescents with ≥3 years of systematic resistance-training experience; such training age likely conferred sufficient neuromuscular adaptation and recovery capacity to manage fatigue within FCMT’s sequential four-exercise structure, reducing the risk that potentiation effects would be obscured by cumulative fatigue. By contrast, the more discrete paired structure of CT may be preferable for novices or athletes with limited training background.

Improvements in either agility, reactive strength, or SSC utilization are effective in enhancing badminton attacking efficiency and reducing joint injuries associated with multi-angle direction changes [5,65]. In addition, the improvement in explosive endurance was effective in enhancing the duration of athletic performance [13,66]. This study has several advantages, as the FCMT group showed significant improvement in lower limb explosive strength, reactive strength, agility, SSC utilization, and explosive endurance compared to the CT group, which suggests that FCMT is effective in enhancing the athletic performance of junior badminton players. The results of this study are consistent with previous research and extended to explore comparisons of explosive endurance, adding credibility and providing coaches with practical suggestions for incorporating FCMT into their training regimens. However, there are some limitations to this study: A) Due to the scarcity of the elite junior badminton athlete population, this study suffers from a small sample size and was conducted only among male athletes. B) The load intensity was not reset in the middle of the experiment considering the accuracy of fatigue monitoring and the purpose of exploring the training acclimatization period, and subsequent studies could further explore the actual effect after resetting the load in the middle of the experiment for the training acclimatization period. C) Considering the consistency between the training actions and the testing actions, an uncommon and innovative assessment method was used to assess explosive endurance changes, and although it has been cited in previous studies, the effectiveness of its assessment and its practical application value still need to be further verified through more research. D) The exercises within the interventions were different. As a result, it is unclear whether the differences observed are due to the different training structures, or simply the different exercises. E) Sleep patterns of participants were not monitored throughout the study. Given that sleep duration and quality significantly influence cognitive function, reaction time, and the ability to produce maximal efforts during both training and testing, especially in tasks requiring explosive power and sustained attention, the lack of sleep control represents a potential confounding variable [67]. Future research should incorporate sleep monitoring to better account for its role in training adaptation and performance outcomes. Despite these limitations, this study effectively demonstrated the value of the FCMT in improving athletic performance.

Based on the results of this study, it is recommended that French contrast method training (FCMT) be incorporated into a training program for adolescent male badminton players. An eight-week intervention program can be designed to adjust the loading intensity in four-week cycles, focusing on the improvement of explosive power, agility, and explosive endurance. Despite the limitations of the study, personalized training programs need to combine FCMT with badminton-specific training and monitoring to guarantee the improvement of athletic performance to meet the athletes’ stage-by-stage fitness needs, as well as to establish athlete profiles with the test data for personalized teaching. Coaches should pay more attention to the alternation of load intensity when arranging complex training, and pay more attention to the timing of training when arranging the French contrast method training. Combining the advantages and limitations of the two training methods, it is recommended that coaches use CT to develop the basic explosive power in the early stage of developing the explosive power quality of young athletes, and arrange FCMT in the strength training in the pre-competition training period to improve the athletes’ performance and competitive level. In addition, it is recommended to choose isometric back squat as a means of high-load activation for FCMT. In summary, this practical approach can lead to a sustained improvement in the competitive performance of badminton players, which is in line with the modern pace of the game.

Conclusion

The present study provides compelling evidence that the French Contrast Method Training (FCMT) is significantly more effective than Complex Training (CT) in enhancing lower limb explosive strength, reactive strength, agility, stretch-shortening cycle (SSC) utilization, and explosive endurance in adolescent male badminton athletes within a short-term training period. While both training modalities improved maximum strength and speed-related performance, FCMT produced superior outcomes across a broader range of neuromuscular adaptations. These advantages may be attributed to the FCMT’s organizational structure and maximizing PAPE activation methods. Additionally, fatigue monitoring revealed that although FCMT had a longer adaptation period than CT, it led to a greater overall performance improvement with a lower cumulative fatigue load. These findings support the integration of FCMT into pre-competition training phases, particularly for youth athletes requiring rapid and sustained explosive efforts, such as those in badminton. Coaches are encouraged to apply FCMT in a periodized manner alongside sport-specific drills to achieve individualized, performance-oriented outcomes.

Acknowledgments

The authors declare that the research was conducted in the absence of any commercial or financial relationships that no conflicts of interest.