Can Complex Training Improve Acute and Long-Lasting Performance in Basketball Players? A Systematic Review

: Basketball demands a sophisticated blend of tactical, technical, physical, and psychological skills, and various methods have been proposed to prepare players for these demands, including resistance training to enhance strength, power, speed, agility, and endurance. Complex training (CT) integrates diverse strength training methodologies by combining heavy-resistance exercises (e.g., squat at 90% of one repetition maximum) with high-velocity movements or plyometrics, both sharing the same biomechanical pattern. However, the optimal application of CT in basketball remains uncertain due to diverse protocols and a lack of consensus in the literature. The aim of this systematic review was to evaluate the acute and chronic effects of CT interventions on physical fitness performance in basketball players and identify the most effective characteristics of moderators. Methods: A bibliographic search was conducted using PubMed, SCOPUS, and Web of Science databases following the Preferred Reporting Items for Systematic Reviews and Meta-analyses guidelines using the PICOS strategy. Results: Fourteen studies met the inclusion criteria, three articles analyzed acute effects, and thirteen analyzed chronic effects. The total number of participants in the studies analyzing acute effects was 50, while for studies examining chronic effects, it was 362. Conclusions: Acutely, CT triggers post-activation potentiation and enhances sprint performance when coupled with brief rest intervals. Over time, these acute improvements contribute to more substantial, long-lasting benefits. Chronic effects of CT improve strength, as evidenced by enhanced 1 RM performance, jumps, sprints, and core muscle strength.


Introduction
Basketball stands as a multidimensional sport, demanding a sophisticated blend of tactical, technical, physical, and psychological [1,2].The sport's complexity reveals itself in the high-intensity actions performed by players interspersed with vital recovery periods [3].These actions encompass explosive jumps, sprints, and changes of direction (CODs), as well as skill-based abilities like shots, dribbling, and rebounds [4].Particularly during critical game phases, these actions wield significant influence over match outcomes.Consequently, the pursuit of enhancing the physical fitness abilities that optimize these critical actions has become a paramount goal for both players and coaches [5].
Performance in basketball-specific activities, such as jumps, sprints, and CODs, has been linked to the strength and power of the lower extremities [6].Strength, defined as the peak tension a muscle or muscle group can generate at a given speed, manifests in diverse forms impacting athletic performance, including power, speed, agility, and endurance [7].The scientific literature presents a broad spectrum of resistance training methods aimed at enhancing the strength and power of basketball players [8,9].These methods encompass a wide range, including body weight-based exercises [10], machine-based resistance training [8], free-weight training [11], Olympic lifts [12], eccentric training [13], and plyometric training [14].Each of these methods consistently showcases improvements in key basketball performance metrics, such as vertical jumps, agility, sprinting, and maximum strength [15].However, the quest to determine the optimal approach for basketball-specific resistance training remains elusive.
In recent years, complex training (CT) has emerged as an approach characterized by the integration of diverse strength training methodologies to address constraints typically associated with their isolated application [15].This method has been referred to by different names, including contrast training (involving one set of high-intensity strength training followed by one set of low-intensity strength exercises), complex training (involving 2-3 sets of high-intensity strength exercises followed by 2-3 sets of low-intensity strength exercises), or combined training (involving high-intensity strength exercises performed at the beginning) [15].This innovative approach pairs a heavy resistance exercise, e.g., squat at 90% of one repetition maximum (1 RM), with a high-velocity movement, both sharing the same biomechanical pattern [16].Typically, a low-intensity plyometric exercise is chosen after a high-intensity strength exercise [15,17].The physiological basis of CT is the phenomenon of post-activation potentiation enhancement (PAPE), which refers to the improvement in muscular performance (i.e., sprint, jump) following maximal or near-maximal muscular contractions [16,18].This stimulation enhances motor unit recruitment and increases the force-producing potential of the utilized musculature.The potentiated state of muscle leads to an immediate boost in performance, and when this is consistently achieved through a structured training program, it results in more significant long-term adaptations compared to other training methods [19].
Research indicates that CT can significantly enhance various physical attributes in basketball players, including sprint speed [7,20,21], jump height [7,[20][21][22], upper body power [23], and muscular strength [20,21].To comprehend the effects of CT, it is essential to distinguish between acute effects, which occur immediately after CT or in the short term (e.g., as a result of employing CT within a warm-up routine) [24,25], and chronic effects, which manifest over the long term (e.g., as a result of incorporating CT into a training regimen) [7,20,26].A recent systematic review by Uysal et al. [15] concluded that CT was more effective in improving the vertical jump performance of young basketball players than other training methods.In this regard, despite the demonstrated potential of CT, there is a lack of evidence and consensus in the literature regarding its optimal application in basketball.On one hand, much of the existing research has primarily focused on team sports in general or specific sports like soccer [17,27].On the other hand, there is considerable variability in the protocols employed for CT, encompassing factors such as the type, intensity, volume, and sequence of exercises, as well as the rest duration between sets and the frequency and duration of training sessions [15].
In light of this, the present systematic review aimed to gather evidence regarding the application of CT in basketball to enhance our understanding of both the chronic and acute effects of this training method, while also providing insight into the characteristics of the moderators utilized in the various programs employed in existing scientific studies.Consistent with previous studies in basketball [15] and other team sports [17], CT would be effective at enhancing specific physical fitness aspects of basketball players.The primary research question guiding this review was What is the impact of complex training on the performance of basketball players.The second question was What are the main characteristics of moderators (i.e., volume, intensity, series, and reps) that optimize the effects of CT.

Materials and Methods
This systematic review adhered to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidance [28].The electronic databases employed for the search included PubMed, Scopus, and Web of Science (WOS), with no temporal limitations.The last search was conducted on 29 December 2023.Keywords were selected using experts' opinions and based on previous reviews conducted on CT in other team sports [15,17,27].The search algorithm using the PICOS approach (population, intervention, comparator, outcomes, and study design) strategy with the following keywords: "basket*" or "complex training" or "contrast training" or "combine training" or "compound training" or "combination of strength training and plyometrics".The search strategy used in PubMed, Scopus, and Web of Science (WOS) was basket* AND ("complex training" OR "contrast training" OR "combine training" OR "compound training" OR "combined strength training and plyometrics" OR "combined resistance training and plyometrics").The reference lists of relevant articles were reviewed to discover additional articles suitable for inclusion in the systematic review.The full search strategies for all databases, including any filters and limits used, are provided in Figure 1.

Elegibility Criteria
The PICOS criteria were employed to select eligible studies.The inclusion and exclusion criteria for this systematic are detailed in Table 1.Duplicate identification was carried out using Mendeley reference management software (v.2.111.0,Copyright © 2024 Elsevier Ltd., Barcelona, Spain).The authors EFG and ARF conducted a screening process for the title, abstract, and reference list of each study to locate potentially relevant studies.A third author (AV) participated in discussions to address any discrepancies in the selection process.

Data Extraction
After identifying and excluding duplicates, the results were exported to an Excel document (Microsoft Office, 2016.Microsoft.Inc., Redmond, Washington, USA), and three tables were created, one for each database.These tables recorded the author's name, date, title, and keywords of all conducted studies, arranged alphabetically based on the first author's name.After reviewing the title and results, the inclusion and exclusion criteria were applied.Data extraction was performed independently by two reviewers (EFG and ARF).The studies meeting the inclusion criteria were reviewed to extract relevant data regarding the effects of CT on physical fitness.The means, standard deviations (SDs), and sample sizes (n) were extracted by one author (EFG) from the included papers and were corroborated by a second (ARF).Any discrepancy between the authors was resolved through discussion with a third author (AVJ).Alongside the results of the fitness tests, the intervention characteristics (i.e., training frequency, total duration, and type of training protocol) and sample details (i.e., sample size, age, and body mass) were extracted and recorded.In instances where data were not explicitly provided in the text but rather were only in a figure [21,29,30], the extraction was performed using a validated graphical software program (WebPlotDigitizer version 4.5; Automeris LLC, Pacifica, CA, USA), previously validated (r = 0.99, p < 0.001) [31] by a single experienced researcher.

Methodological Quality Assessment
The risk of bias in the studies was determined using the Tool for the Assessment of Study Quality and Reporting in Exercise (TESTEX) scale [32] applied in similar CT studies [15,17].This tool comprises 12 assessment criteria, with a maximum score of 15 points.Higher scores reflect lower study bias.Reference values categorize a study's risk of bias as high (≤4 points and below), medium (4-11 points), and low (≥11 points) [15].Two independent researchers (EFG and AV) conducted the assessments, and in the event of conflicts, a third author (ARF) facilitated discussions until a consensus was reached.

Study Selection and Identification
A total of 807 documents were obtained (228 from PubMed, 266 from Scopus, and 313 from WOS).Duplicates (n = 292) were removed, and 595 studies' abstracts were screened, of which 498 were removed.Of the 24 articles eligible for full-text analysis, 14 were included in our review.Ten were excluded based on the following reasons: (i) not in basketball (n = 7); (ii) other types of reviews (n = 3).

Acute Effects of Complex Training
Table 3 presents the characteristics of studies that analyzed the acute effects of complex training.Table 4 shows the results of studies analyzing the acute effects of CT on performance in basketball players.The table presents the values obtained in the tests used by the studies following the acute application of CT, along with the reported effect size and p-value (taken directly from the studies).The studies evaluated the acute impact of CT through a countermovement jump (CMJ) [30,33] and a single-leg jump (SLJ) [30] to assess jump ability, focusing on factors such as height.Agility performance was assessed using the Shuttle Test [33] and the modified t-agility test (MAT) [30].Sprinting performance was measured using 10-30-m linear sprint tests [29].The acute effects of CT were analyzed immediately [29,30,33] and after 5 min [29].

Discussion
Given the existing research's primary focus on general team sports or specific sports like soccer, and the considerable variability in CT protocols (i.e., exercise type, load, volume, sequence, rest duration, and training frequency), there is a need for a systematic review that specifically addresses the acute and chronic effects of CT in basketball players.The primary purpose of this systematic review was to determine the acute and chronic effects, as well as the moderators (i.e., volume, intensity, series, and reps) characteristic of complex training (CT) in basketball players.This review included a total of 14 articles and 412 participants.The main findings indicate that CT training induces improvements in athletes' physical performance both in the acute (i.e., short term) and chronic (i.e., long term) realms, especially in critical areas such as jump height, lower body strength, and change of direction ability.It was also found that this type of training was more effective than regular basketball training independently of age, regarding physical fitness performance in players.The load moderators in studies analyzing the acute effects of CT are characterized by performing 2-4 sets of 5-12 reps at 85% 1 RM, including explosive exercises before or after resistance exercise [33], 2 sets of 4 repetitions of back squats at 80% 1 RM and 10 bi or unilateral drop jumps [30], and 5 sets at 8RM for half-squats [29].Factors such as the program duration (≥6 weeks), the intensity of conditioning activity (<85% 1 RM), and the rest interval between sets (≥2 min) appear to influence the positive response to CT in team sports [16,42,43].The main characteristics of the interventions' moderator effects of CT in long-term performance included intervention duration (6-10 weeks), intervention frequency (2-3 sessions per week), sets per session for a given exercise (1-12 sets), repetitions per set (3-15 repetitions), and set intensity (40-85% 1 RM or 0.8-1.0m/s).However, the studies had a certain level of heterogeneity regarding the nature of the interventions (i.e., sex, age, or competitive level) and moderating variables (i.e., load, repetitions, or duration of intervention).
Within the acute effects of CT, several relevant aspects are highlighted.Biel et al. [33] demonstrated similar effects on jump capacity (CMJ and SLJ) regardless of the order of exercises (first resistance or first explosive) in CT.Moreover, performing CT with unilateral or bilateral exercises did not yield different acute effects on jump capacity or COD [30].It has been observed that both isometric and dynamic conditioning activities have been shown to be effective in inducing the PAPE effect, suggesting that the specific selection of the type of conditioning activity may not be crucial for the manifestation of the phenomenon [44][45][46].However, fatigue produced in the activities performed may influence the acute response, as suggested by the possible negative impact on men due to fatigue generated by the protocol.Along with this, Tsimahidis et al. [21] demonstrated that CT acutely improves sprint performance at 10 and 30 m after 5 min but not immediately after its application.However, it is important to consider interindividual variability in the response to conditioning activity, suggesting the need for further studies to address this issue [47].In addition, limitations of the study are noted, such as the lack of a crossover design and the possibility that the order of assessment and training volume influenced the results.The findings from these studies highlight the complexity of the acute effects of CT and the need for a more complete understanding of its underlying mechanisms and the factors that may modulate its efficacy in basketball players.
The meta-analysis conducted by Pagaduan and Pojskic [48] primarily focused on the chronic effect of CT on vertical jump performance in basketball players.Similarly, this study identified significant improvements in vertical jump performance through CT compared to traditional resistance training or plyometric training.However, our review went a step further by evaluating the effects of CT not only on different manifestations of vertical jump but also on other performance-related tests in basketball players' physical fitness.Yañez-García et al. [38] demonstrated significant improvements in sprints (10 and 20 m sprint times) after CT regardless of age (U13, U14, and U17 basketball players).However, the results from other studies are contradictory; some studies have not shown CT effects on sprint improvement [37], while others have reported significant but similar effects to the control group, making this habitual training [7].Conversely, some studies have shown improvements in sprint time [21] and speed [29] in 10 m and 30 m tests following CT application.The different durations of the intervention (6-10 weeks), participants' ages (8-18 years), and load characteristics may have influenced these results.These more nuanced findings contribute to a more comprehensive understanding of how CT impacts not only vertical jump performance but also many other physical aspects.
Furthermore, regarding the chronic effects of CT, studies have explored its impact on the strength of basketball players, including assessments of 1 RM through exercises such as the Half Squat [7,20,21,29,38], Back Squat [37], Bench Press [20], and Hip Thrust [20] and more specific tests such as the medicine ball throw [22].CT has demonstrated its efficacy in enhancing 1 RM performance in exercises like the Full Squat [38], Half Squat [21,29], and Back Squat [37].Similarly, Freitas et al. [20] observed comparable effects of CT when utilizing both optimal loading CT alone and modified CT (80% 1 RM + optimal load), leading to positive outcomes in the Half Squat (ES = 0.64), Bench Press (ES = 0.11-0.15),and Hip Thrust (ES = 0.98-1.23).These findings support the effectiveness of CT, which combines heavy-resistance exercises with explosive exercises to stimulate improvement in strength in basketball players.On the other hand, CT has also been shown to be effective in improving the medicine ball throw [22] and specific core muscle strength (i.e., core muscle strength stability or sit-up abdomen test) when applied in the training of this musculature [34].
This review carries certain limitations, including not factoring in individual discrepancies among athletes in terms of initial strength levels, strength training experience, and muscle fiber structure.These factors can significantly impact the efficacy of complex training.Further, the methodological quality of the studies incorporated varied, with scores ranging from 9 to 13 points for studies inspecting acute effects [29,30,33] and scores ranging from 5 to 11 points for those examining chronic effects [7,[20][21][22]26,29,[33][34][35][36][37][38]40].These limitations should be considered when interpreting the results as they may introduce potential biases and uncertainties.
Notwithstanding these limitations, the findings add to the burgeoning body of evidence supporting the benefits of CT in improving basketball performance.These findings are of considerable importance to basketball coaches and athletes, as they indicate that integrating complex training into regular training routines could potentially optimize performance.Future investigations should strive to address these limitations by accounting for individual differences among athletes and probing the optimal intensity and duration of complex training for achieving maximal performance improvements.Although our assessment was extended until December 29, 2023, we acknowledge the incorporation of an additional study, not initially covered in our review [49].Despite the diligence in capturing all pertinent literature accessible during the review period, the ever-evolving landscape of research in this domain may lead to the emergence of new studies subsequent to this review.
The findings of this systematic review underscore the practical importance of incorporating CT into the training regimens of basketball players to optimize both acute and chronic performance.Specifically, for acute improvements, CT has shown significant positive effects on jump ability, agility, and sprint performance.Coaches can implement CT protocols that include 2-4 sets of 5-12 reps at 85% 1 RM, incorporating explosive exercises either before or after resistance exercises to enhance jump and sprint performance within short recovery periods.Regarding chronic improvements, this study indicates that a wellstructured CT program can lead to substantial long-term gains in various performance metrics, including jump height, lower body strength, and change of direction ability.Effective CT programs typically last 6-10 weeks, with 2-3 sessions per week, and use loading parameters of 1-12 sets per session, with repetitions ranging from 3-15 and intensity levels between 40 and 85% 1 RM or 0.8 and 1.0 m/s.These protocols have been shown to be more effective than regular basketball training alone, benefiting players across different ages and competitive levels.Additionally, CT can be adapted to enhance specific strength aspects, such as maximal strength in exercises like the Half Squat, Back Squat, and Bench Press, by employing 2-4 sets at higher intensities (80-85% 1 RM) over a duration of at least six weeks.This tailored approach allows for the development of explosive strength, which is crucial for basketball performance.

Conclusions
In conclusion, this systematic review highlights the positive impact of CT on physical performance in basketball players.Unlike previous reviews, our study is specific to basketball and includes both acute and chronic effects.This systematic review also covers performance improvements across various tests, such as jumping, sprinting, strength, and endurance.CT has been shown to improve jump height, lower body strength, and change of direction ability, regardless of age or training level.Acutely, CT induces post-activation potentiation and enhances sprint performance with brief rest intervals.Chronically, CT enhances strength, including 1 RM performance-specific tests and core muscle strength.Factors such as the program duration, intensity, and rest intervals influence CT's effectiveness.Despite some limitations, these findings support the integration of CT into basketball training routines to optimize performance.

Figure 1 .
Figure 1.Diagram flow of the review.

Table 1 .
Selection criteria used according to PICOS model.

Table 2 .
Methodological quality score of the studies included in the review using the Tool for the Assessment of Study Quality and Reporting in Exercise.

Table 3 .
Characteristics of studies that analyzed the acute effects of complex training.

Table 4 .
The mean ± standard deviation of fitness variables reported for the acute use of complex training and control/comparison conditions in the included studies.

Table 5 .
Characteristics of studies that analyzed long-lasting effects of complex training in basketball players.

Table 6 .
The mean ± standard deviation of fitness variables reported for the long-lasting complex training and control/comparison conditions in the included studies.