Heavy resistance training has been shown to be the most effective way to improve maximal strength (1,7,21). Periodized resistance training programs consisting of multiple sets of exercises performed for 6 or fewer repetitions with loads corresponding to at least 85% of one-repetition maximum (1RM) have been suggested to maximize muscular strength gains (11,21). Heavy weights appear necessary to optimally stimulate the nervous system (13), and neural adaptations are critical to optimal strength training (12,27). However, increases in strength plateau over time. For the athlete who competes in maximal strength events, that is, power lifting and strongman/woman competitions, strength plateaus need to be minimized during training. Thus, additional training methods may be necessary to bring about further strength gains.
Another potential method to enhance muscular strength is to specifically target the neuromuscular system via high-power movements (2,15,16,21). High-velocity, ballistic movements (that limit deceleration of the resistance) selectively recruit higher-threshold, fast-twitch motor units (19). In addition, high-velocity plyometric training has been shown to enhance stretch-shortening cycle activity, fiber cross-sectional area, and skeletal muscle contractile properties (17,24,28). Taken together, these neuromuscular changes may lead to increased maximal strength expression.
Power is the product of force and velocity; therefore, peak power is attained when the optimal combination of these variables is used during muscle contraction. It has been shown that peak power output is attained using a wide range of loads corresponding to ∼15-60% of 1RM for ballistic exercises such as the jump squat and ballistic bench press (4,5,19,30). The wide range of loading reported has been attributed to the nature of the exercise (i.e., muscle mass involvement, single vs. multiple joint), training experience, methods used to measure power output, and strength level of the subjects (9,19). Power training (i.e., light-to-moderate loading performed with explosive repetition velocities) has been shown to increase isometric strength and rate of force of development (13). In the elderly, high-velocity power training has been shown to increase maximal dynamic strength (8,14). In addition, McBride and colleagues (25) reported that ballistic resistance training increased 1RM squat by 8-14%, and Malisoux and colleagues (24) reported that 8 weeks of plyometric training increased leg press 1RM by 12%. Thus, the additional power development (and subsequent neuromuscular adaptations) derived from ballistic training could be beneficial in enhancing maximal dynamic strength.
Because ballistic training itself can enhance maximal dynamic strength (24,25), and the combination of weight and plyometric training has been shown increase muscle activation to a greater extent than weight training alone (28), it appears plausible that the addition of ballistic resistance training to traditional heavy resistance training may be useful for enhancing 1RM strength and potentially augment muscular strength more than traditional training alone due to enhanced rate of force development. However, there is a void in the literature, particularly for those athletes who compete in maximal strength events, as to the efficacy of the addition of ballistic training to a traditional heavy resistance training program. Thus, the purpose of this investigation was to examine the effects of a combined ballistic and heavy resistance training program on maximal strength in the lower and upper extremities. It was hypothesized that the combined ballistic and heavy resistance training program would produce a greater increase in upper/lower-body maximal strength than heavy resistance training alone in recreationally trained men.
Experimental Design and Approach to the Problem
To address the primary hypothesis of this investigation, we matched recreationally resistance-trained men for muscle strength, body size, and age, and we subsequently randomly assigned them to 1 of 2 training groups: (i) a heavy-resistance, traditional resistance training group (HR) or (ii) a combination heavy-resistance plus ballistic resistance training group (COM). This design enabled us to examine whether or not the addition of ballistic training to traditional resistance training augmented muscular strength improvements to a greater extent than traditional resistance training alone. Muscular strength and power assessments were performed before and after 8 weeks of training to evaluate the effects of both resistance-training programs.
Seventeen men (age = 20.7 ± 1.5 years, height = 178.9 ± 6.0 cm, body mass = 81.8 ± 11.9 kg) volunteered for this investigation. Each subject had previous lifting experience (3.4 ± 2.1 years) and initiated the study in a trained state. None of the subjects were taking any medications, anabolic steroids, or nutritional supplements known to affect resistance exercise performance. In addition, subjects received nutritional counseling, completed a 3-day dietary recall document, and were carefully instructed to maintain diet throughout the experimental period. The study was approved by The College of New Jersey's Institutional Review Board, and each subject signed a written informed consent document before participation. In addition, none of the subjects had any physiological or orthopedic limitations that could have affected lifting performance as determined by completion of a health history questionnaire before initiating the study. Subjects were subsequently matched and randomly placed into 1 of 2 training groups: (i) a heavy-resistance, traditional resistance training group (HR) or (ii) a combination heavy-resistance plus ballistic resistance training group (COM). Subject characteristics are presented in Table 1.
Maximal strength testing took place on 2 separate occasions, before and after 8 weeks of training. The 1RM bench press and squat were used to assess maximal upper- and lower-body strength, respectively, at a standard time of day using standardized procedures (22,26). For each exercise, a warm-up set of 5-10 repetitions was performed using 40-60% of the perceived maximum 1RM. After a 1-minute rest period, a set of 2-3 repetitions was performed at 60-80% of the perceived maximum 1RM. Subsequently, 3-4 maximal trials (1-repetition sets) were performed to determine the 1RM. For the bench press, any trials that involved “cheating,” such as excessive arching of the back or bouncing of the weight, were discarded. For the squat, each subject descended to the “parallel” position where the greater trochanter of the femur was aligned with the knee and ascended until full knee and hip extension. A research assistant was located lateral to the subject and gave a verbal signal “up” to ensure proper range of motion. Rest periods in between trials were 2-3 minutes in length. A complete range of motion and proper technique was required for each successful 1RM trial. Each testing session was supervised by a certified strength and conditioning specialist.
Power testing was performed 48 hours after strength testing. Upper- and lower-body power were measured using the ballistic push-up and jump squat on a portable force plate (Advanced Mechanical Technology, Inc., Watertown, MA). For the ballistic push-up, each subject was instructed to place his hands in the center of the force plate with his feet on the floor in a standard push-up position. The subjects proceeded to perform 2 sets of 6 consecutive ballistic push-ups (with only their body weight) separated by 5 minutes of rest. For the jump squat, each subject descended to a near-parallel position and subsequently jumped as high as possible while minimizing any contributions from the arms (16,26). The weight was safely released upon jumping via the equipment's hydraulic braking system (Cormax Squat/Overhead Press System 1000, Cormax Strength Power Systems, Valley City, ND). The jump squat was performed with 30% of the pretraining squat 1RM (30). The best trial and average of each trial were recorded for analysis. Testing order was randomized such that half of the subjects performed the jump squat first and the other half performed the ballistic push-up first. Test-retest reliability coefficients were r > 0.90 for all strength and power tests.
Percent body fat was estimated using a 3-site skinfold caliper test. The 3 sites measured were the chest, abdomen, and thigh, and percent body fat was calculated using the methods of Jackson and Pollock (18). Lean body mass (LBM) was calculated using the following equation: Fat mass = body mass x % fat; LBM = body mass - fat mass. Percent body fat and LBM were assessed before and after the 8-week training period.
Base Resistance Training Phase
Before maximal strength and power testing, each subject participated in a mandatory base resistance training phase. The purpose of this phase was to (i) instruct subjects on proper lifting technique; (ii) familiarize subjects to the testing exercises (i.e., bench press, ballistic bench press, squat, and jump squat); and (iii) ensure subjects initiated the study in a trained state (26). The base training phase lasted two weeks and consisted of three mandatory sessions per week for a total of six sessions.
Each group trained 3 alternating days per week for 8 weeks after 2 upper/lower body split routine workouts of similar volume (Tables 2 and 3). The frequency selected enabled adequate recovery in between workouts (as each major muscle group was trained 1-2 times per week) thereby reducing the potential effects of overreaching. The training programs followed a variation of a linear periodized model targeting maximal strength improvements where the intensity increased while the volume decreased over time. The periodized HR training program included 2 phases. The first phase required the subjects to perform 3-4 sets of 6-8 repetitions with approximately 80-85% of their 1RM for core exercises. The second phase consisted of 4 sets of 4-6 repetitions with approximately 85-90% of their 1RM for core exercises. The periodized program for COM was similar to HR with the exception that 2 ballistic exercises replaced 2 traditional exercises each workout. The first phase consisted of 4 sets of 5 repetitions (50% of 1RM) and the second phase consisted of 5 sets of 3 repetitions (60% of 1RM) for those high-velocity ballistic exercises similar to the bench press and squat. Ballistic exercises were performed early in the workout in sequence followed by the traditional strength exercises (1).
Standard statistical methods were used to calculate means and standard deviations which were used to describe all performance data. A 2 × 2 repeated-measures analysis of variance was used to analyze all performance data. Subsequent Tukey's post hoc tests were used to determine pairwise differences when significant F ratios were obtained. For all statistical tests, a probability level of P ≤ 0.05 was established to denote statistical significance.
Lean body mass increased significantly in both groups with no differences observed between groups: HR = 69.5 ± 8.1 (pre) to 71.8 ± 8.4 (post) kg; COM = 69.3 ± 10.5 (pre) to 71.4 ± 9.9 (post) kg. In addition, percent body fat decreased significantly in both groups with no difference observed between groups: HR = 14.1 ± 5.3% (pre) to 12.8 ± 4.8% (post); COM = 15.5 ± 5.0% (pre) to 14.7 ± 3.5% (post).
Maximal strength data are presented in Figure 1. Both groups significantly increased 1RM bench press and squat strength from pre to post training. A significant interaction (P = 0.04) was observed only for the bench press indicating that the increase observed in COM was greater than the increase observed in HR.
Changes in muscle power are presented in Table 4. No significant main effects were observed from pre to post training in absolute or relative peak and average powers produced during the jump squat and ballistic push-up. However, a significant interaction was observed (P = 0.02) for average jump squat power. The differences from pre to post in HR (-397W) and COM (+478W) were statistically significant between groups.
The results of the present study indicated that the addition of ballistic exercises into a traditional heavy resistance training program can augment increases in 1RM bench press in recreationally trained men. Furthermore, average lower-body power also can be significantly enhanced with the addition of ballistic exercises to a traditional resistance training program. However, the hypothesis that the addition of ballistic exercises to heavy resistance training would augment 1RM squat was not supported in the present study.
The unique finding in the present study was that the addition of ballistic exercises to traditional heavy resistance training augmented 1RM bench press strength more than traditional resistance training alone. The COM group increased 1RM bench press by 12.1% whereas the HR group increased 1RM bench press by 7.4%. Although previous studies have examined strength increases in resistance-trained individuals who performed heavy resistance and power training (3), to our knowledge this was the first study to specifically quantify dynamic strength increases from the addition of ballistic training to heavy resistance training. It was hypothesized that improvements in power gained through the inclusion of ballistic exercises may enhance force production especially during the initiation of bar ascent. During initial ascent, a sufficient amount of power must be expressed in order to accelerate the bar through the “sticking point” of the exercise. Elliot et al. (10) defined the sticking region as a force-reduced transition phase between a strain energy-assisted acceleration phase and a mechanically advantageous maximum strength region. Additional power gained in this region could increase the likelihood of reaching the area of maximal strength thereby increasing 1RM strength to a greater extent. These results have important implications for those individuals who compete in maximal strength events (i.e., power lifting) as our data indicate maximal bench press performance can be enhanced by addition of ballistic exercises to traditional heavy resistance training.
Although mechanisms for augmented 1RM bench press performance in COM were not elucidated, it is interesting to examine potential reasons for greater muscle strength gains via the addition of ballistic training to heavy resistance training. Enhanced neural activation (i.e., increased motor unit recruitment, firing rate, synchronization, or some combination of these) of agonist musculature has been shown following training (27,29,31). Considering that ballistic training is a potent stimulus to the neuromuscular system, enhanced neural function (beyond that of weight training alone) could have contributed to the augmented upper-body strength improvement. Increased myotatic (stretch) reflex activity, neuromuscular stiffness, and ability to store and use elastic energy may occur following ballistic training (17,28). In combination, these adaptations could contribute to enhanced performance and muscle activation during the concentric phase when preceded by an eccentric muscle action. Considering that 1RM bench press performance is highly dependent on concentric muscle strength; it is possible that augmented stretch-shortening cycle activity could have contributed to the augmented strength enhancement. Finally, plyometric training has been shown to alter skeletal muscle contractile properties. Malisoux and colleagues (24) examined 8 weeks of plyometric training and reported fiber type transitions (IIx to IIa), 22-30% increases in fiber cross-sectional area, 18-29% increases in single fiber contraction velocity, and 25-49% increases in fiber peak power (consistent with enhanced cross-bridge mechanics). In addition, the authors suggested that plyometric exercise differed from resistance training in that shortening velocity increased substantially across all fiber types in compensation for low-to-moderate force enhancement during plyometric training (24). Thus, it is possible that enhanced contractile properties of skeletal muscle contributed to the augmented 1RM bench press in the COM group.
Interestingly, the addition of ballistic training to heavy resistance training did not augment 1RM squat performance in the present study. Although both HR and COM groups increased 1RM squat by 17.3% and 15.2%, respectively, these improvements were not significantly different between groups. These data are in contrast to Hoffman et al. (15), who observed greater improvements in 1RM squat in an Olympic training group than those observed in a traditional power lifting group. The lack of augmentation observed in lower-body strength compared to upper-body strength in the COM group is unclear. However, a few explanations may be postulated. It is possible that the addition of upper-body ballistic training in the COM group led to augmentation of the bench press partially due to training status. Although our subjects were recreationally resistance-trained (and completed base resistance training prior to initiating the study), they had more experience with the bench press exercise than the squat. Thus, it is possible they may have still been in a learning phase for the squat which could have masked potential adaptations resulting from ballistic training. If this was the case, the changes observed in the bench press may have reflected greater familiarity which may indirectly suggest that the addition of ballistic training to heavy resistance training may have a greater potential effect when individuals have attained a threshold level of muscle strength and can be used as a technique to surpass training plateaus.
Another potential reason entails training specificity. The high pulls and jump squats performed in the present study may not have been specific enough to enhance 1RM squat strength. For safety reasons, jump squats were performed on specialized ballistic equipment (Cormax Squat/Overhead Press System 1000, Cormax Strength Power Systems, Valley City, ND) with a hydraulic braking system that limited loading during the eccentric phase. In addition, the range of motion (i.e., slightly above the parallel thigh position) of the jump squat and high pull exercises may not have been specific enough to the range of motion and motor patterns used in a free weight 1RM squat. If our original hypothesis was correct and the addition of ballistic training to enhance power at the sticking region was critical to augmenting 1RM performance, then the lack of specificity to the sticking region of a free weight barbell squat may have limited potential 1RM gains. Furthermore, the unloading of the eccentric phase could have played a role. This is consistent with the data of Hoffman et al. (16) who demonstrated the importance of the eccentric phase in developing maximal power.
Interestingly, no significant main effects in power improvements were observed in either group. However, a significant interaction was observed in jump squat average power where the decrease in power in HR (-397 W) and increase in COM (+478W) was statistically different. Although 6% to 13% mean improvements were observed in jump squat and ballistic push-up peak and mean power in COM, these values did not reach statistical significance. The lack of significant improvement in upper- and lower-body power in the COM group may be attributed to the relatively small sample size (n = 8 in the COM group) and the high degree of variance associated with power measurements. Due to the traditionally large numerical values associated with measuring power (4,5,20,23), the lack of a large sample size and subsequent low-to-moderate statistical power (0.30-0.63) observed in the power measurements may have masked the mean increases observed in the present study. Other studies have failed to denote statistical significance in power data despite substantial mean differences when N sizes of 17 or less were used (20,23). Thus, it is likely that a larger sample size would have been needed to denote significant main effects in power enhancement in the present study.
The significant interaction observed in average jump squat power demonstrated that combined heavy resistance and ballistic training has a beneficial effect on enhancing lower-body power. Interestingly, a slight insignificant reduction in average jump squat power was observed in HR. These results concur with research that has shown that heavy resistance strength training alone could potentially have a negative impact on lower-body power (6). Our results demonstrate the importance of inclusion of exercise-specific ballistic resistance exercises into a resistance training program in order to enhance lower-body muscular power.
In conclusion, the results of the present study provide evidence that the inclusion of ballistic exercises into a heavy resistance training program can enhance maximal upper-body strength and lower-body power. These results have positive implications for the inclusion of ballistic training for those athletes who are striving to increase 1RM maximal strength.
Maximal strength of the squat and bench press is critical to anaerobic athletes who compete in sports such as power lifting or strength competitions. Over time, training plateaus may occur and other means of maximizing strength may be critical for progression. The results of the present study indicate that the inclusion of ballistic training to heavy resistance training can augment maximal upper-body strength. It may be hypothesized that power enhancement, especially at the sticking region of the bench press, could contribute to an increase in 1RM bench press. Therefore, strength athletes who compete in upper-body strength events may benefit from the inclusion of ballistic training. In addition, the limited power improvements observed in the present investigation suggest that a more specific training program may be needed for those individuals whose primary goal is maximal power enhancement.
We would like to thank a dedicated group of subjects for their participation. In addition, we would like to thank the National Strength and Conditioning Association for funding this study.
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