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nemius fascicle length decreased only after complex training. (211.8 6 9.4%, p = 0.006). Muscle fiber cross-sectional areas increased only after complex training ...
MUSCLE STRENGTH, POWER, AND MORPHOLOGIC ADAPTATIONS AFTER 6 WEEKS OF COMPOUND VS. COMPLEX TRAINING IN HEALTHY MEN ANGELIKI-NIKOLETTA STASINAKI,1 GIORGOS GLOUMIS,1 KONSTANTINOS SPENGOS,2 ANTHONY J. BLAZEVICH,3 NIKOLAOS ZARAS,1 GIORGOS GEORGIADIS,1 GIORGOS KARAMPATSOS,1 GERASIMOS TERZIS1

AND

1

Athletics Laboratory, School of Physical Education and Sport Science, University of Athens, Athens, Greece; 2First Department of Neurology, Eginition Hospital, Medical School, University of Athens, Athens, Greece; and 3School of Exercise and Health Sciences, Edith Cowan University, Joondalup, Australia ABSTRACT

Stasinaki, A-N, Gloumis, G, Spengos, K, Blazevich, AJ, Zaras, N, Georgiadis, G, Karampatsos, G, and Terzis, G. Muscle strength, power, and morphologic adaptations after 6 weeks of compound vs. complex training in healthy men. J Strength Cond Res 29(9): 2559–2569, 2015—The aim of the study was to compare the effects of compound vs. complex resistance training on strength, high-speed movement performance, and muscle composition. Eighteen young men completed compound (strength and power sessions on alternate days) or complex training (strength and power sets within a single session) 3 times per week for 6 weeks using bench press, leg press, Smith machine box squat, and jumping exercises. Preand posttraining, jumping and throwing performance and maximum bench press, leg press, and Smith machine box squat strength were evaluated. The architecture of vastus lateralis and gastrocnemius muscle was assessed using ultrasound imaging. Vastus lateralis morphology was assessed from muscle biopsies. Jumping (4 6 3%) and throwing (9 6 8%) performance increased only with compound training (p , 0.02). Bench press (5 vs. 18%), leg press (17 vs. 28%), and Smith machine box squat (27 vs. 35%) strength increased after both compound and complex training. Vastus lateralis thickness and fascicle angle and gastrocnemius fascicle angle were increased with both compound and complex training. Gastrocnemius fascicle length decreased only after complex training (211.8 6 9.4%, p = 0.006). Muscle fiber cross-sectional areas increased only after complex training (p # 0.05). Fiber type composition was not affected by either intervention. These results suggest that short-term strength and power training on

Address correspondence to Gerasimos Terzis, [email protected]. 29(9)/2559–2569 Journal of Strength and Conditioning Research Ó 2015 National Strength and Conditioning Association

alternate days is more effective for enhancing lower-limb and whole-body power, whereas training on the same day may induce greater increases in strength and fiber hypertrophy.

KEY WORDS ballistic training, muscle architecture, combined resistance training, power performance INTRODUCTION

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esistance training is an effective method for increasing both muscular strength and power (14). Indeed, several studies have shown that just a few weeks of resistance training may increase strength, power, and functional performance in powerdemanding activities as a result of both neural and muscular adaptations (12). Additionally, a number of studies have shown that the combination of strength and power training is at least equally, and in some cases more effective for improving muscular power compared with either strength or power training alone (2,7,13,17). Several methods of combining strength and power training have been proposed. One of these, described as compound training, includes strength and power training on different/alternate days (9,20,21). This method usually involves strength training with high resistances (70–90% 1 repetition maximum [1RM]) in 1 session and ballistic training or plyometric training with lower resistances (e.g., ;30% 1RM or with body mass) on a different day. Studies using this model have shown that short term (4–6 weeks) of compound training can improve both lower-body (21) and upper-body (20) power production. In a different training approach described as complex training, strength and power exercises are performed in pairs within the same session: a set of high-resistance strength exercise followed by a set of a biomechanically similar lowerload, high-speed exercise (13). Both strength and power are increased after 4–11 weeks of complex training (5,17,26). Part of the positive effect of complex training has been attributed to the mechanism of postactivation potentiation, where the VOLUME 29 | NUMBER 9 | SEPTEMBER 2015 |

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Complex vs. Compound Training and Muscle Power performance in a set of exercise is enhanced when performed a short time after a preceding set (13,24). However, little is known about the superiority of either compound or complex in the development of power performance and the neuromuscular adaptations induced by these 2 training methods. In a recent study, 4 weeks of compound and complex training resulted in similar increases in vertical jump height and maximum power in collegiate volleyball players (21) indicating that there may be some similarity in the adaptations elicited by the 2 forms of training. One difficulty with developing an understanding of the potential differences in the effects of compound and complex training, especially after short exposures, is that the neuromuscular adaptations have not been described. Combinations of strength training elements on the same or different days have been found to result in decreases in type I and increases in type IIA myosin heavy chain isoform percentages (20,22). Nonetheless, there is a lack of information regarding the potential adaptations in muscle fiber cross-sectional areas, so the possible functional influence of these myosin heavy chain alterations cannot be well predicted. Muscle thickness and pennation (fascicle angle) have been shown to increase after short periods (5 weeks) of combined strength and power training on different days (9). However, these limited data do not allow for hypotheses to be developed as to whether similar muscle size or architecture advantages might be obtained through compound and complex training, or whether they are associated with changes in muscle strength and power development. Therefore, the aim of this study was to compare the effects of compound and complex training programs on performance in whole- and lower-body muscular strength and high-speed movement performance in athletic healthy individuals. Additionally, muscle morphology and architecture were evaluated to provide further insights in the muscular adaptations elicited by the training programs.

METHODS Experimental Approach to the Problem

To compare the effectiveness of compound and complex training programs, young males participated in 6 weeks of either compound or complex resistance training with equal number of sets and repetitions. Another group of young males served as control and did not participate in any training. Strength and power performance as well as muscle architecture and morphology were evaluated before and after the training period in all groups. Specifically, countermovement jumping was used to test lower-body power performance, and backward overhead throwing performance was measured as a marker of whole-body extension power. Because both complex and compound types of training are resistancebased training programs, muscular strength was evaluated in all of the 3 exercises used for training (leg press, bench press, Smith machine box squat). Muscle architecture was determined with B-mode ultrasonography in vastus lateralis and gastrocnemius muscles (agonist muscles in leg press, Smith

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machine box squat, and jumping). Muscle morphology was evaluated by analyzing biopsy samples from vastus lateralis for muscle fiber cross-sectional area and type before and after the training period. Subjects

Twenty-five young male moderately trained physical education students (age: 21.9 6 1.9 years, height: 179.2 6 5.1 cm, mass: 75.3 6 7.2 kg) gave their written consent to participate in the study after being informed of the experimental procedures and the possible hazards of the exercise training and testing and the muscle biopsy procedures. Subjects had modest experience with resistance training through their participation in university courses but had not performed any systematic resistance training during the previous year. However, they continued performing athletic throwing skills training for 2 hours per week with very light intensity during the training period. They were assigned to 1 of 3 groups ensuring there were no differences in pretraining countermovement jump and overhead throw performance (described below): compound training (N = 9), complex training (N = 9), and control group (N = 7; see Table 1). Two subjects of the compound group did not finish the training program because of personal reasons unrelated to the study. All procedures were approved by the local ethics committee. Procedures

Training. Training was performed 3 times per week for 6 weeks. The compound group performed slow-speed, highload (i.e., strength) and high-speed, low-load (power) training on alternate days, whereas the complex group performed strength- and power-based sets in the same session in pairs, that is, 1 strength exercise set followed by 1 power-based exercise set (13); Table 2. Exercises included the incline (458) leg press, bench press, and box squat in a Smith machine, always performed in this order. For the box squat that was performed in a Smith machine, subjects started the upward movement after touching an adjustable bench with their glutei, allowing a knee angle of 908. The compound group performed 4 3 6RM on a strength training day and 4 3 8 repetitions at 30% 1RM (measured at pretraining and adjusted as described later) with a maximumspeed concentric phase plus 3 3 8 drop jumps (described below) on a power-based training day. A rest interval of 3–5 minutes was imposed between sets and exercises, respectively. The complex group performed 2 3 6RM, and 2 3 8 repetitions at 30% of 1RM (paired exercises), plus 3 3 8 drop jumps on every other training day (Table 2). Threeminute intervals were imposed between complex pairs and 5 minutes between exercises. The strength training loads were increased weekly so as to maintain the 6RM loading. These loads were then used to estimate 1RM (6), which was then used weekly to adjust the 30% of 1RM load used for power training. Drop jumps were performed with hands placed on hips from 40 cm during the first 3 weeks and

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TABLE 1. Physical characteristics, whole- and lower-body high-speed movement (power) performance, and muscular strength capacity for the compound group (N = 7), the complex group (N = 9), and the control group (N = 7), before and after the training.*

Anthropometry Age (y) Mass (kg, initial) Height (cm) CMJ (cm) Before After % Change Cohen’s d Backward overhead throw (m) Before After % Change Cohen’s d 1RM leg press (kg) Before After % Change Cohen’s d 1RM box squat (kg, Smith machine) Before After % Change Cohen’s d 1RM bench press (kg) Before After % Change Cohen’s d

Compound

Complex

Control

22.3 6 2.7 73.5 6 4.6 177.0 6 2.8

21.9 6 2.3 77.3 6 8.0 179.2 6 0.1

21.3 6 1.5 75.0 6 9.0 178.9 6 5.0

46.7 6 4.0 48.8 6 5.3 4.0 6 3.0† 0.490

46.2 6 6.8 46.1 6 6.5 21.4 6 6.3 20.011

51.4 6 6.7 50.8 6 6.3 21.2 6 2.0 20.096

9.96 6 0.9 10.56 6 1.3 9.23 6 7.6† 0.926

10.57 6 1.5 10.96 6 1.3 4.30 6 8.1 0.251

10.73 6 0.9 10.72 6 0.9 20.11 6 0.6 20.012

259.0 6 18 305.0 6 38 17.7 6 10† 2.529

302.0 6 35z 388.0 6 58z 28.0 6 7† 2.450

254.0 6 33 250.0 6 33 21.7 6 3.2 20.132

151.0 6 11 191.0 6 15† 27.2 6 8.1† 3.713

181.0 6 41z 243.0 6 47z 35.6 6 12.0z§ 1.532

162.0 6 20 160.0 6 21 21.3 6 1.4 20.105

111.0 6 10 117.0 6 9 5.0 6 5† 0.542

107.0 6 22 124.0 6 19 18.4 6 15z§ 0.780

116.0 6 10 115.0 6 11 21.3 6 2 20.139

*Data are given as mean 6 SD. †Significant difference after training. zSignificant difference between compound and complex, for the corresponding time point. §Significant difference in the percentage change between compound and complex training.

45 cm thereafter. Subjects were instructed to minimize the contact time after the first landing and to take-off as fast as possible. In total, 4 training sessions were missed across the groups (2 for the compound group and 2 for the complex group) and no subject missed more than 1 (compliance for compound 98.4% and for complex 98.7%). Both groups performed the same number of exercises and repetitions (total number of repetitions 1,512 for each group) and at the same relative intensities. At the end of the training period, each subject in both groups had performed 108 sets of strength exercises and 108 sets of ballistic exercises (except from the missed sessions described before). The % volume load (exercises 3 sets 3 repetitions 3 %1RM) was the same for both groups. However, the absolute volume load (exercises 3 sets 3 repetitions 3 kilograms) was higher in the complex group because they were stronger at the beginning of the training (Table 1), and their strength was increased at a higher

rate in Smith machine box squat and bench press. For example, the complex group was 16% stronger in leg press at the beginning of the training and 27% stronger at the end of the training compared with the compound group (Table 1). Accordingly, leg press volume load was 15% higher for the complex group compared with the compound group at the beginning of the training (initial 2 sessions: 8,115 6 1,485 vs. 7,057 6 1,246 kg) and 25% higher at the end of the training period (last 2 sessions: 10,387 6 1,899 kg vs. 8,327 6 1,287 kg). Whole- and Lower-Body High-Speed Movement (Power) Performance. Backward overhead throwing performance was measured as an indicator of whole-body extension power. It was measured outdoors on a standard shot put circle, during the morning hours with a 6-kg shot (ambient temperature 20–238 C). While holding the shot with both hands, it was lowered rapidly to a position to the front of, but VOLUME 29 | NUMBER 9 | SEPTEMBER 2015 |

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Complex vs. Compound Training and Muscle Power

TABLE 2. Overview of the compound and the complex training programs.* Compound Day 1

Sets 3 repetitions Leg press 436 Bench press 436 Smith box squat 4 3 6

Intensity (% 1RM) 85% 85% 85%

Sets 3 repetitions Leg press throw 4 3 8 Bench press 438 throw Squat jump 438 Drop jumps 338

Intensity (% 1RM) 30% 30%

Exercise

Day 2

Complex

Exercise

30% 40–45 cm

Day 1

Exercise

Repetitions

Leg press Leg press throw Leg press Leg press throw Bench press Bench press throw Bench press Bench press throw Smith box Squat

6 8 6 8 6 8 6 8 6

Intensity (% 1RM) 85% 30% 85% 30% 85% 30% 85% 30% 85%

Squat jump Smith box Squat

8 6

30% 85%

Squat jump Drop jumps

8 338

30% 40–45 cm†

*In complex, training was performed with these characteristics for every session. Three-minute rest intervals were allowed between sets with 5-minute intervals between exercises. Three sessions per week were performed for both groups; for example, Monday, Wednesday, and Friday. The compound group and the complex group performed the same number of repetitions: Compound = 4 sets 3 6 repetitions 3 3 exercises 3 9 sessions = 648 repetitions of strength training and 4 sets 3 8 repetitions 3 3 exercises 3 9 sessions = 864 repetitions of power training. Sum = 1,512 repetitions. Complex = 2 sets 3 6 repetitions 3 3 exercises 3 18 sessions = 648 repetitions of strength training and 2 sets 3 8 repetitions 3 3 exercises 3 18 sessions = 864 repetitions of power training. Sum = 1,512 repetitions. †Performed every other training day.

between, the knees then accelerated upward and released over the head behind the body. The goal was to achieve maximum distance, and subjects were instructed (with feedback after each throw from the researcher) to throw at just less than a 458 angle (i.e., optimum angle = ;428). The task requires forceful extension of hips, knees, ankles, back, and shoulders and is thus considered an excellent test of wholebody extension power. Subjects started with a short warmup: 5 minutes jogging, stretching of the major muscle groups, and 5 backward overhead throws with progressively increasing intensity. Then, 3 maximal efforts were allowed for each subject with a 2-minute rest, and the longest throw was used in analysis. The Intraclass correlation coefficient (ICC) for throwing performance on 2 different days in a different group of subjects has been shown to be acceptable: 0.93 (23,28). The vertical jumps were performed indoors 15 minutes after the throwing test using the “jump and reach” method. Briefly, subjects were instructed to stand at the side of a wall and draw a line with a chalk at the highest level in the standing posture. This measured their standing reach. The subjects then performed a countermovement jump as high as possible, with 1 hand on the hip and the other hand free to draw another line on the wall. The distance between the maximum jump touch height and the standing reach was considered as the jump height. After performing 3 submaximal jumps with

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increasing intensity, subjects performed 3 maximal jumps with a 1-minute rest between (ICC = 0.98, p = 0.004, 95% CI = 0.870–0.990, n = 26). Subjects were instructed to jump as high as possible, attempting to reach line targets drawn on the wall. The best performance was used for analysis. The validity of the jump and reach test has been examined in our laboratory before, while performing jumps with maximum effort on a contact mat (Tesys Suite Ergo System, Globus Sport & Health Technologies, Codogne, Italy, r = 0.96, p , 0.001). Maximum Strength (1RM) Leg Press, Bench Press, and Smith Machine Box Squat Tests. One RM assessment was performed for the incline leg press (458), bench press, and Smith machine box squat on a separate day according to previous descriptions (7). After a 5-minute warm-up on a stationary bicycle (heart rate: 120–140 b$min21) and static stretching exercises (20 seconds 3 2, for each major muscle group), subjects performed incremental efforts until they were unable to lift a heavier load. Ten repetitions with moderate resistance were performed in the first warm-up set and 3–5 repetitions in the next 2 sets with approximately 10% load increment in each of these sets. Then, single-repetition sets were performed with 2.5–5% load increments until subjects were unable to lift a heavier load (6–7 multiple-repetition and single-repetition sets in total). Three minutes of rest was allowed between sets. Maximal strength was determined

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Journal of Strength and Conditioning Research for all 3 of the exercises in the same day with 20 minutes of rest between each strength test with the abovementioned order. For the Smith machine box squat, the lower limit for the downward movement was set at 908 knee angle. During a pilot assessment on an earlier day, the subjects’ right hip, knee, and lateral malleolus were marked with a sticker, and the exact point of the lower level of the glutei when knee angle was 908 was measured. Thereafter, an adjustable bench was placed under the subjects’ glutei, so as to prevent any further downward movement while squatting during training or testing. During measurement and training, subjects were starting the upward movement immediately after touching the adjustable bench with their glutei. Muscle Architecture. All ultrasound images before and after the training were obtained during the morning hours. The posttraining ultrasound images were obtained 5 days after the last training session and 2 days after performing the maximum strength tests. B-mode ultrasound images were obtained from the right vastus lateralis and gastrocnemius using a 45-mm linear probe (6.5 MHz, MicroMaxx Ultrasound System; SonoSite, Bothell, WA, USA). For vastus lateralis, subjects laid supine with their knees fully extended and their muscles relaxed. Sonographs were taken in the middle of the muscle at 50% of the distance from the central palpable point of the greater trochanter to the lateral condyle of the femur (8). For gastrocnemius images, subjects laid prone with their knees fully extended, their feet hanging off the edge, and were asked to leave their feet rested and their muscles relaxed so that ankle angle was in a physiological position. Sonographs were taken at the proximal level 30% of the distance between the popliteal crease and the center of the lateral malleolus (18). A watersoluble gel was applied to the transducer to aid acoustic coupling and reduce the needed pressure from the probe against the muscle. The transducer was placed longitudinal at femur or tibia, oriented in parallel to the muscle fascicles and perpendicular to the skin. However, because of individual differences, the transducer was sometimes aligned slightly diagonally to the longitudinal line of the muscle. The transducer’s alignment was considered appropriate when several fascicles could be easily outlined without interruption across the image (8). Images were analyzed for muscle thickness, fascicle angle, and fascicle length with image analysis software (Motic Images Plus 2.0, Motic, Hong Kong). Muscle thickness was defined as the mean of the distances between the superficial and deep aponeurosis measured at the ends of each 45-mm wide sonograph, fascicle angle as the angle of insertion of muscle fascicles onto the deep aponeurosis, and fascicle length as the fascicular path between the insertions of the fascicle onto the upper and deeper aponeurosis. When the fascicle extended off the image, the length of the missing portion of the fascicle was estimated by linear extrapolation of both the fascicular path and the

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aponeurosis (4). The error introduced by these techniques depends on the degree of curvature of the fascicle and is less than 2.3% (22). The reliability for the measurement of muscle thickness (ICC = 0.976 [95% CI: 0.954–0.988], p , 0.001), fascicle angle (ICC = 0.862 [95% CI: 0.746–0.928], p , 0.001), and fascicle length (ICC = 0.834 [95% CI: 0.700– 0.911], p , 0.001) was determined on 2 consecutive days by the same investigator (n = 36). Muscle Biopsies and Histochemistry. Vastus lateralis muscle samples were obtained from the middle portion of the muscle with Bergsrto¨m needles under local anesthesia with 2% lidocaine. The pretraining sample was obtained 20 cm from mid-patella and the posttraining sample 5 cm proximally. The posttraining biopsies were obtained 5 days after the last training session and 2 days after performing the maximum strength tests. After reporting to the laboratory subjects rested in a supine position for 10 minutes before, ultrasound evaluation was performed (described above). Biopsy samples were obtained 10 minutes after the ultrasound evaluation. Samples were aligned, placed in embedding compound, and frozen in isopentane precooled to its freezing point. All samples were kept at 2808 C until the day of analysis. Serial cross sections of 10-mm thick were cut at 2208 C and stained for myofibrillar ATPase after preincubation at pH 4.3, 4.6, and 10.3. Samples obtained before and after the training period from each subject were incubated in the same session in the same jar. A mean of 305 (range: 225–385) muscle fibers from each sample were classified as type I, IIA, or IIX. The cross-sectional area of all classified fibers from each sample was measured with an image analysis system (ImagePro; Media Cybernetics, Inc., Silver Spring, MD, USA) at a known and calibrated magnification. Statistical Analyses

All data were analyzed using SPSS statistical software (version 21); all data reports are given as mean 6 SD. Separate analyses of variance with repeated measures were performed to evaluate differences in each variable between groups. Fisher’s Least Significant Difference (LSD) test post hoc tests were used to further examine pairwise differences where statistical significance was reached. Repeatedmeasures analysis of covariance (ANCOVA) was used when a significant difference was found between compound and complex groups at pretest. Paired-sample t-tests were performed to evaluate training-related changes within groups and independent-sample t-tests to examine difference in training-related changes between groups. Pearson’s (r) product-moment correlation coefficients were computed to explore the relationships between variables. p # 0.05 was used as a 2-tailed level of significance.

RESULTS Countermovement jump height increased significantly with compound (46.7 6 4.0 cm to 48.8 6 5.3 cm, Cohen’s VOLUME 29 | NUMBER 9 | SEPTEMBER 2015 |

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Complex vs. Compound Training and Muscle Power d = 0.490, p = 0.02; Table 1), whereas it remained unchanged with complex training (46.2 6 6.8 cm to 46.1 6 6.5 cm, Cohen’s d = 20.011, p = 0.42), and the change in countermovement jump height after compound training tended to be higher compared with complex training (p = 0.056). Similarly, overhead throwing performance was increased with compound training 9.2 6 7.6% (Cohen’s d = 0.926, p = 0.02) but not with complex training (Cohen’s d = 0.251; Table 1). The percentage changes (%) in countermovement and throwing performance with compound training were significantly correlated (r = 0.75, p , 0.01). Moreover, when all subjects considered as a group, the percent changes in countermovement jump height and overhead throwing performance were significantly correlated with the percent changes in vastus lateralis thickness (r = 0.78 and 0.52, respectively, p # 0.05). Leg press, bench press, and Smith machine box squat 1RM were increased after both compound and complex training (Table 1). The increase in Smith machine box squat and bench press strength was significantly greater after complex compared with compound training (p # 0.05). When the effect of the pretest leg press strength was removed (repeated-measures ANCOVA), there was no difference in the increase in 1RM leg press strength between compound and complex training (p = 0.331). The complex group had higher strength values in leg press and Smith machine box squat compared with the compound group

both before and after training (p , 0.01). Bench press strength was not different between the compound and complex groups, both before and after training (Table 1). The percent changes in leg press strength were significantly correlated with the percent changes in type I and type II vastus lateralis fiber cross-sectional area (r = 0.63 and 0.57, respectively, p # 0.05), but no correlations were observed for fiber composition or muscle architectural variables. Body mass was not significantly altered after training in either group. Significant increases in vastus lateralis muscle thickness (16.5 6 8.5%, p = 0.001) and fascicle angle (26.1 6 14.0%, p = 0.002) were found with compound training (Table 3). Likewise, complex training induced increases in vastus lateralis thickness (7.1 6 7.0%, p = 0.02) and fascicle angle (19.9 6 22.6%, p = 0.04); however, the percentage increase in vastus lateralis thickness was higher after compound compared with complex training (p # 0.05). The percent changes in vastus lateralis thickness were negatively correlated with the percent changes in vastus lateralis fascicle length (r = 20.76, p # 0.05). Significant increases in gastrocnemius fascicle angle were found with compound (5.3 6 6.0%, p = 0.048) and complex training (14.3 6 7.6%, p , 0.001). The percentage increases in gastrocnemius fascicle angle were higher after complex compared with compound training (p # 0.05). Moreover, a significant decrease was found in gastrocnemius fascicle length with complex training (211.8 6 9.4%,

TABLE 3. Vastus lateralis and gastrocnemius medialis architecture before and after 6 weeks of compound (N = 7) and complex (N = 9) training.* Vastus lateralis

Compound Before After % Change Cohen’s d Complex Before After % Change Cohen’s d Control Before After % Change Cohen’s d

Gastrocnemius

Thickness (cm)

Fascicle angle (8)

Fascicle length (cm)

Thickness (cm)

Fascicle angle (8)

Fascicle length (cm)

2.3 6 0.3 2.7 6 0.4† 16.5z 1.118

13.6 6 2.6 17.0 6 3.0† 26.1 1.288

9.6 6 1.2 9.8 6 1.7 2.1 0.129

2.1 6 0.4 2.1 6 0.4 0.0 0.098

23.6 6 3.9 24.9 6 4.9† 5.3 0.357

5.7 6 0.5 5.7 6 0.9 0.0 0.023

2.5 6 0.2 2.7 6 0.2† 7.1 0.839

16.0 6 4.0 18.5 6 2.1† 19.9 0.633

9.5 6 1.4 8.8 6 1.3 27.0 20.497

2.1 6 0.3 2.2 6 0.3 4.7 0.498

23.7 6 3.4 27.0 6 3.4† 14.3§ 0.960

5.7 6 0.5 5.0 6 0.5†z 211.8§ 21.298

2.4 6 0.3 2.3 6 0.3 3.6 20.149

14.9 6 3.3 14.6 6 3.7 2.0 20.077

9.8 6 1.2 9.6 6 1.2 21.0 20.083

2.1 6 0.2 2.1 6 0.2 0.6 0.073

21.8 6 2.5 21.8 6 1.3 0.7 0.006

5.7 6 0.4 5.7 6 0.4 0.9 0.086

*Data (mean 6 SD) are also shown for the control group (N = 7). †Significant difference after training. zSignificant difference between compound and complex, for the corresponding time point. §Significant difference in the percentage change between compound and complex training.

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Figure 1. Vastus lateralis fiber cross-sectional area before and after 6 weeks of compound or complex training. §Significant difference between compound and complex; *significant difference from pre- to posttraining; #significant difference in the change between compound and complex.

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p = 0.006), whereas there was no change with compound training. The percent changes in gastrocnemius fascicle angle were positively correlated with the changes in gastrocnemius thickness and negatively correlated with gastrocnemius fascicle length (r = 0.55 and 20.56, respectively, p # 0.05). There was a significant correlation between the initial vastus lateralis thickness and the percent change in vastus lateralis thickness (r = 20.58, p # 0.05) and the percent change in vastus lateralis fascicle angle (r = 20.57, p # 0.05). Before training, type I muscle fiber cross-sectional area was larger in the complex group compared with the compound group; however, type I (5,686 6 1,165 mm2 to 6,193 6 1,272 mm2, Cohen’s d = 0.436, p = 0.004), IIA (6,691 6 1,378 mm2 to 7,654 6 1,511 mm2, Cohen’s d = 0.699, p = 0.02), and IIX (5,419 6 1,306 mm2 to 6,103 6 1,570 mm2, Cohen’s d = 0.524, p = 0.046) fiber cross-sectional area increased only with complex training (Figure 1). However, when the effect of the pretest type I cross-sectional area was removed (repeated-measures ANCOVA), there was no difference in the increase in type I fiber cross-sectional area between compound and complex training (p = 0.003). Interestingly, the ratio of the % increase in type I and II fiber CSA and the % increase in training volume load was significantly higher in complex compared with compound training (p # 0.05). The percentage area of type II muscle fibers was significantly larger after compound compared with complex training (68.3 6 11.3% compared with 55.5 6 7.7%, p # 0.05) but not before training. There

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Complex vs. Compound Training and Muscle Power were no significant changes in the ratio of type IIA:I crosssectional area with complex or compound training. Of interest, the compound group had a greater proportion of type II fibers than the complex group both before and after training (compound type II fibers before 60.8 6 8.2%, after 64.7 6 9.0%; complex before 49.1 6 8.2%, after 52.1 6 6.1%), but no changes in fiber type composition were detected after the training (Figure 2). Percentage changes in vastus lateralis architecture were not correlated with the changes in vastus lateralis morphology (e.g., correlations between the percent change in vastus lateralis fiber crosssectional area [for any fiber type] and the percent change in vastus lateralis fascicle angle were low, r , 0.03, ns).

DISCUSSION

Figure 2. Vastus lateralis fiber type composition before and after 6 weeks of compound and complex training. No statistical significant differences were found after either intervention group. §Significant difference between compound and complex.

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The main finding of this study was that high-speed movement (power) performance was significantly increased after 6 weeks of compound but not after complex training, whereas squat and bench press strength improved more with complex compared with compound training. These results suggest that performing strength and power training sessions on alternate days (compound training) is more effective for improving explosive muscle performance compared with complex training but strength is increased more with complex training. The cross-sectional areas of vastus lateralis muscle fibers were selectively increased only after complex training, which is in concert with the greater percentage increase in squat strength in this group. It cannot be excluded that the higher improvement in muscle strength after complex training might be triggered by the higher

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Journal of Strength and Conditioning Research absolute loads used in this group because of the higher initial strength. However, the ratio of the % increase in type I and II fibers CSA and the % increase in training volume load was significantly higher in complex compared with compound training, suggesting that complex training resulted in a higher fiber hypertrophy than compound training relative to the training volume performed. This implies that complex training is more effective in increasing muscular strength compared with compound training. In the only previous study comparing compound and complex training (4 weeks, 2 sessions per week) in collegiate volleyball players, Mihalik et al. (21) found similar increases in vertical jump height after compound (9%) and complex training (5%). The difference in the effectiveness of the complex program in that previous study (i.e., increase with complex training) and this study (no increase with complex training) might relate to either the different training background of the subjects or the different training intensities used; it has been proposed that complex training may benefit experienced strength trainers more than lesser trained individuals (24). Furthermore, in the study by Mihalik et al., the training intensity was set at 60% of 1RM, and the plyometric exercises were performed without external load. In this study, strength exercises were performed with 4 sets of 85% of 1RM (6RM) and ballistic exercises with 30% of 1RM. This higher intensity of training might have imposed a different neuromuscular load by reducing movement speeds, increasing total force requirements and eliciting greater neuromuscular fatigue. Importantly, fatigue and potentiation coexist after voluntary contractions (24) and if fatigue prevails then lesser training adaptations might be anticipated. Nonetheless, the rest between 1 strength set and the subsequent ballistic set in complex training was 3 minutes, which has previously proposed to be sufficient given that postactivation potentiation seems to be nearmaximal in voluntary contractions after ;3–4 minutes (24). Regardless, the significant increase in countermovement jump height and backward overhead throw performance and the correlation between the percentage changes in these tests only after compound training in this study underpins the notion of superiority of this type of training in developing lower-body muscle explosive performance compared with the complex training, at least for moderately trained subjects. Vastus lateralis muscle thickness and fascicle angle were increased after both compound and complex training. These results are in agreement with those of Blazevich et al. (9), who found significant increases in vastus lateralis muscle thickness and fascicle angle after 5 weeks of strength and power training on different days. Interestingly, a change in muscle fiber cross-sectional area is often considered to be an important factor driving fascicle angle change (10). Nonetheless, the data obtained presently for vastus lateralis are not in agreement with this hypothesis because increases in fiber cross-sectional area occurred in the complex only group,

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whereas increases in fascicle angle were observed in both training groups, and changes in fiber cross-sectional area did not correlate with changes in vastus lateralis fascicle angle. Moreover, changes in vastus lateralis thickness were not correlated with changes in vastus lateralis fascicle angle. In contrast, the percentage changes in gastrocnemius thickness correlated moderately with the changes in gastrocnemius fascicle angle (r = 0.55, p # 0.05). This might point to a different adaptation process or a different recruitment pattern between vastus lateralis and gastrocnemius with the training program used here. Interestingly, gastrocnemius fascicle length decreased 11% after complex training in this study and was reduced in all complex subjects (data not shown). This is an interesting and novel finding, potentially related to the greater enhancement of muscular strength after this type of training being accompanied by a lack of change in muscle thickness and an increase in fascicle angle. In concert with the decrease in gastrocnemius fascicle length, small but nonsignificant reductions in vastus lateralis fascicle length after complex training were observed, suggesting some similarity in adaptation in vastus lateralis and gastrocnemius and potentially underpinning the lack of increase in power performance in this group. Fascicle length is often considered to be reflective of the number of sarcomeres in series in the muscle fibers and is presumably associated with faster fiber shortening velocities (8,10), so the reduction in gastrocnemius fascicle length after complex training might theoretically have attenuated the increase in muscle power despite the presence of increases in fiber cross-sectional area. Strength training consistently results in a muscle fiber type shift from type IIX to type IIA (1,3). In contrast, a frequent finding is that power training results in a preservation of the percentage of type IIX muscle fibers (19,25,27,28). Similarly, the combination of strength and power training tends not to induce reductions in the percentage of type IIX muscle fibers (e.g., 20). The present data support these findings as the training (ballistic/jumping) caused no detectable reduction in the percentage of type IIX muscle fibers. Furthermore, the current results suggest that performing power training either in the same session or on alternate days to strength training may actually preserve the type IIX muscle fiber proportion, minimizing the shift to type IIA. The preservation of type IIX muscle fibers might be an advantage for muscular power production, as these fibers have faster contraction velocities, power, and rate of tension development compared with type IIA and I fibers (11,15). This might have important applications for performance in power-based sports during yearround athletic preparation, when strength training is often combined with power training by athletes. In agreement with this concept, a relatively high percentage of type IIX muscle fibers was found in vastus lateralis of elite hammer throwers at the end of their winter preparation period, when strength training volume was maximized but power training was concurrently performed (23). VOLUME 29 | NUMBER 9 | SEPTEMBER 2015 |

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Complex vs. Compound Training and Muscle Power Enhancement of power performance largely depends on both muscular and neural adaptations. Unfortunately, neural adaptations were not evaluated in this study, although this component might have been of great importance because the subjects were only moderately trained and the duration of the study was relatively short. Little is known about the potential neural adaptations associated with combined strength and power training. Eight weeks of combined strength and power training has been reported to increase jumping performance and vastus lateralis electromyographic (EMG) signal amplitudes but decrease gastrocnemius EMG (6). In contrast, Walker et al. (26) found that 11 weeks of complex training improved jumping performance without a detectable change in vastus lateralis EMG. Thus, there is no clear picture of the neural adaptations after combined strength and power training. Likewise, adaptations in tendon mechanical properties such as stiffness might have contributed to the differential strength/power adaptations between compound and complex training. Future studies should address this question, as there are no current data on tendon adaptations with combined strength and power training. Another limitation of the study was that the subjects were assigned to the training groups according to their initial countermovement jump and overhead throwing performances without considering physiological data such as the fiber type composition (which were analyzed at the study’s completion). Subjects in the complex group were initially stronger in leg press and Smith machine box squat and also had a greater type I muscle fiber cross-sectional area. The phenomenon of acute postactivation potentiation seems to be different in stronger compared with weaker individuals (16); however, this remains to be evaluated in longitudinal studies comparing compound and complex training. Finally, it cannot be overlooked that the structure of the training stimuli used in this study might have influenced the results in a different way; the compound group trained with alternate heavy and light days, whereas the training load was constant over the 18 training sessions for the complex group. The load variation in compound training might be considered as training periodization, which could have induced power enhancement. Unfortunately, this is an inherent difficulty in studies comparing the outcome of the implementation of training programs with constant characteristics such as the present one; future studies should address this issue perhaps by implementing well-structured periodized compound and complex training programs.

PRACTICAL APPLICATIONS The present results suggest that short-term strength and power training on alternate days (compound) may be more effective in enhancing high-speed movement (power) performance compared with training for strength and power in the same day (complex). In a large number of sports, training regimens must contain both strength and power components. In such instances, it seems that when the aim is to

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improve power performance such as jumping ability, strength and power training should be performed on alternate days. In contrast, when training contains both high-load and low-load sets of the same multijoint exercise (e.g., 1 Smith machine box squat set with 85% 1RM followed by a jump squat with 30% 1RM), muscle hypertrophy should be anticipated together with increases in muscular strength. For instance, the increase in bench press and squat strength may be notably higher after 6 weeks of complex (strength and power training in the same day) compared with compound training. However, this type of training combination will probably not induce major increases in power performance such as jumping or throwing.

ACKNOWLEDGMENTS The authors express their gratitude to the subjects of this study. The results of this study do not constitute endorsement of the product by the authors or the National Strength and Conditioning Association.

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