Adam M. Gonzalez, PhD, NSCA-CSCS, CISSN, Assistant Professor of Health Professions, Hofstra University
Exercise Science Program
Exercise science and sports nutrition research strives to advance the field of exercise physiology, and the community at large, by bridging the gap between science and application.
Exercise scientists seek to improve the knowledge base of strength and conditioning practitioners by conducting studies on topics such as sets and reps for optimizing resistance training programs, the physiological responses to training, and the effectiveness of dietary strategies.
As an exercise physiologist and educator, I strive to conduct research in the areas of sport science, exercise physiology, and nutritional supplementation. My primary research interests include exercise and nutritional strategies to optimize body composition, maximize health and performance, and enhance adaptations to resistance exercise. With the assistance of my colleagues and students, we have had the opportunity to publish several research studies to further expand our understanding of muscle physiology, exercise program design, and nutritional supplementation.
Enhancing adaptations to resistance exercise
Maintaining skeletal muscle mass and function is critical for disease prevention, mobility, quality of life, and whole-body metabolism. Resistance exercise is known to be a primary regulator for promoting gains in muscle size and strength; however, the resistance exercise parameters for maximizing muscular adaptations remain unclear. We have recently set out to compare common resistance training programs and variables to provide science-based recommendations for strength and conditioning professionals.
Hypertrophy vs. Strength Resistance Training Protocols
Resistance training paradigms are often divided into protocols designed to promote an increase in either hypertrophy or strength. Hypertrophy-style protocols typically involve greater volume (3-6 sets; 8-12 repetitions), moderate intensities (<85% 1 repetition maximum [1RM]), and short rest intervals (30-90 seconds), whereas strength-style protocols typically involve higher intensities (>85% 1RM), low volumes (2-6 sets; <6 repetitions), and longer rest intervals (3-5 minutes). My colleagues and I have recently published a series of papers comparing hypertrophy- and strength-style resistance training. We have investigated hormonal, immune, and metabolic responses; intramuscular anabolic signaling; muscle growth, strength, and power; and muscle activation during these two common styles of weight training. Most recently, our work published in Muscle & Nerve 1 investigated the electromyographical (EMG) activation of the muscle during resistance exercise at 70% vs. 90% 1RM. Our findings indicated that across a set to repetition failure, 90% 1RM produced greater muscle activation during the leg press exercise; however, similar peak EMG was observed during the final common repetitions of each set. These findings provide support to our acute and chronic studies, which have shown that emphasis on either training volume or intensity may be effective for maximizing muscular hypertrophy when utilizing relatively heavy loads. In our acute studies published in European Journal of Applied Physiology2 and Physiological Reports,3 we showed that both hypertrophy- and strength-style resistance exercise protocols elicit similar intramuscular anabolic signaling, despite significant differences in markers of muscle damage and the hormonal response. Subsequently, in our 8-week training study published in Physiological Reports,4 we compared a hypertrophy-style training program (70% 1RM; 4 x 10-12 repetitions; 1-minute rest intervals) and a strength-style training program (90% 1RM; 4 x 3-5 repetitions; 3-minute rest intervals) in resistance-trained men. Pre- and post-training assessments included lean body mass via dual energy X-ray absorptiometry; muscle cross-sectional area and thickness of the vastus lateralis, rectus femoris, pectoralis major, and triceps brachii muscles via ultrasonography; and strength in the back squat and bench press exercises. After 8 weeks of training, the strength-style routine stimulated significantly greater gains in lean arm mass and bench press strength compared with the hypertrophy-style routine. However, no other differences between protocols were noted for measures of lean body mass, muscle size, or strength. The greater gains in some measures of muscle size and strength observed after the strength-style routine indicate that using a greater intensity load might provide a superior stimulus for muscle hypertrophy and strength in trained men. Thus, these results provide evidence that strength development among well-trained individuals may be realized with greater intensity loads. Ultimately, the research supports the notion that maximal strength benefits are obtained from the use of heavy loads, while muscle hypertrophy can be equally achieved across a spectrum of loading ranges.5
Optimal Rest Intervals for Resistance Exercise Performance and Muscular Adaptation
Among several other resistance training parameters, including intensity, volume, and frequency, interset rest interval length is an important consideration. How long should you rest in between sets when performing resistance exercise? In search of the answer, I recently conducted an extensive literature search and published a brief review in Strength and Conditioning Journal 6 to discuss the effect of interset rest interval length on resistance exercise performance, the acute hormonal and metabolic response, and training-induced muscular adaptation. Common dogma has recommended restricting rest interval (<1.5 minute) to promote muscle growth solely based on the transient elevation in hormones and metabolic responses observed in the post-workout period. However, the majority of literature does not support the hypothesis that training for muscular hypertrophy requires shorter rest intervals than training for strength development. In fact, our review paper published in Sport Medicine 7 concluded that transient increases in the hormonal milieu after resistance exercise was not related to exercise-induced muscle hypertrophy.
Several studies have shown that the number of repetitions performed during a resistance-training bout may be compromised with shorter rest intervals. During compound exercises, such
as bench press or back squat, a 3- to 5-minute rest interval has been shown to produce less performance decrements when compared to a rest interval that is less than 2 minutes. Since training intensity and volume seem to be reduced proportionally as rest interval length is reduced during multi-joint resistance exercise, it appears that at least 2-3 minutes of rest between sets would provide sufficient recovery so as not to compromise total workout volume and subsequent hypertrophy and strength outcomes. For assistance or single-joint exercises, a shorter rest interval of 1-2 minutes may suffice.
All things considered, rest interval recommendations depend on several factors, including training intensity, complexity of the given exercise, type of muscle contraction, activated musculature, exercise order, training status, and strength level. Therefore, it is difficult to precisely define an optimal rest interval, and it could be argued that on a global basis, it may not exist. Ultimately, several rest intervals can be implemented within a periodized training model to achieve the desired physiological adaptations. Manipulation of training variables, including rest interval, is always dependent on the specific training goals of the individual.
Nutritional supplementation is a multibillion-dollar industry, with more than 70% of young adults reporting the use of at least one supplement. Energy drinks and multivitamins, along with muscle building and weight loss supplements, are among the most popular supplements on the market. However, because products marketed as dietary supplements do not require preapproval from the Food and Drug Administration, there seems to be a pill, powder, or bar that claims just about every health benefit out there. It is important for consumers to understand the benefits and risks associated with dietary supplementation, and the only way to truly understand if a nutritional supplement is useful is through vigorous randomized, double-blind, placebo-controlled research. We recently tested the efficacy of several popular supplements and multi-ingredient products. Below are descriptions of our research and results.
Phosphatidic Acid Supplementation
Phosphatidic acid has shown to be a key player in stimulating muscle protein synthesis following exercise by serving as an intracellular lipid second messenger, which mediates protein signaling activity. Therefore, researchers have questioned if dietary supplementation of phosphatidic acid can further increase muscle gains. Given that the preliminary research on this ingredient has yielded inconclusive evidence, we set out to determine the effects of phosphatidic acid supplementation on muscle thickness and strength in resistance-trained men. The purpose of this study 8 was to investigate the effects of phosphatidic acid supplementation on muscle thickness and strength following an 8-week, supervised resistance-training program. Fifteen resistance-trained men followed an 8-week, supervised resistance-training program and were randomly assigned to a group that consumed either 750 mg of phosphatidic acid or a placebo. Pre- and post-testing included muscle thickness of the rectus femoris, vastus lateralis, biceps brachii, and triceps brachii muscles via ultrasonography, along with strength assessment of the squat, deadlift, and bench press exercises. All participants experienced significant improvements in each measure of muscle thickness and strength; however, the phosphatidic acid supplementation did not further enhance training-induced muscular adaptations. In conclusion, supplementation of 750 mg phosphatidic for 8 weeks in conjunction with a supervised resistance-training program did not have a differential effect compared to a placebo on changes in muscle thickness or strength.
Recovery from high-intensity exercise is vital for overcoming fatigue and building muscle. ß-Hydroxy-ß-methylbutyrate (HMB) supplementation has shown to improve recovery by increasing muscle protein synthesis and decreasing muscle protein breakdown. HMB is a metabolite of the amino acid leucine, meaning that when we eat protein, a small percentage gets converted to HMB. To get an effective dose of HMB (~3 grams) from your diet, you would need to eat 60 grams of leucine, which would be about 600 grams of high-quality protein. Thus, supplementation is the more practical option. Calcium-HMB has been the most popular form, but recently, HMB-free acid has been shown to have a greater absorption rate and bioavailability, which has been suggested to provide a superior stimulus for exercise recovery. In collaboration with colleagues in Brazil, I published a systematic review in Nutrition Research9 examining the effect of HMB-free acid supplementation on recovery and muscle adaptations after resistance training. When combined with resistance training, HMB-free acid supplementation may attenuate markers of muscle damage, augment acute immune and endocrine responses, and enhance training-induced muscle mass and strength. HMB-free acid supplementation may also improve markers of aerobic fitness when combined with high-intensity interval training. Nevertheless, more studies are needed to determine the overall efficacy of HMB-free acid supplementation as a nutritional supplement.
Citrulline Malate Supplementation
Pre-workout nutritional supplementation has become increasingly popular among recreational and competitive athletic populations as a means of boosting exercise performance. Recently, citrulline malate has garnered much attention for its potential to increase nitric oxide (NO) production, which may enhance resistance exercise performance. The potential beneficial effects of citrulline malate may be attributed to the synergistic combination of both L-citrulline and malate at the cellular metabolic level. L-citrulline is a nonessential amino acid that functions as a precursor to L-arginine, which synthesizes NO when catalyzed by the enzyme nitric oxide synthase. Malate is an intermediate of the tricarboxylic acid cycle, and supplementation may augment energy production and increase the rate of adenosine triphosphate (ATP) production. My colleagues and I recently published a study in the Journal of Strength and Conditioning Research10 investigating the effect of citrulline malate supplementation on upper-body resistance exercise performance. Twelve recreationally resistance-trained men underwent two testing sessions administered in a randomized, double-blind fashion. During each visit, participants were provided with either 8 grams of citrulline malate or a placebo 40 minutes prior to initiating a barbell bench press resistance exercise protocol consisting of 5 sets of 15 repetitions at 75% 1RM with 2-minute rest intervals. The results showed that supplementation with 8 grams of citrulline malate did not increase exercise performance, augment the muscle swelling response to training, or alter subjective measures of focus, energy, and fatigue in recreationally resistance-trained men. Although preliminary studies have reported small, but significant, increases in resistance exercise performance following citrulline malate supplementation, our study did not support this notion. Future research is necessary to further evaluate the acute and chronic effects of citrulline malate supplementation on resistance training outcomes.
- Gonzalez, A. M. (2016). Acute anabolic response and muscular adaptation after hypertrophy-style and strength-style resistance exercise. The Journal of Strength & Conditioning Research, 30, 2959-2964.
- Gonzalez, A. M. (2016). Effect of interset rest interval length on resistance exercise performance and muscular adaptation. Strength & Conditioning Journal, 38, 65-68.
- Gonzalez, A. M., Ghigiarelli, J. J., Sell, K. M., Shone, E. W., Kelly, C. F., & Mangine, G. T. (2017). Muscle activation during resistance exercise at 70% and 90% 1-repetition maximum in resistance trained men. Muscle & Nerve, 56, 505-509.
- Gonzalez, A. M., Hoffman, J. R., Stout, J. R., Fukuda, D. H., & Willoughby, D. S. (2015). Intramuscular anabolic signaling and endocrine response following resistance exercise: Implications for muscle hypertrophy. Sports Medicine, 46: 671-685.
- Gonzalez, A. M., Hoffman, J. R., Townsend, J. R., Jajtner, A. R., Boone, C. H., Beyer, K. S., Baker, K. M., Wells, A. J., Mangine, G. T., & Robinson, E. H. (2015). Intramuscular anabolic signaling and endocrine response following high volume and high intensity resistance exercise protocols in trained men. Physiological Reports, 3, e12466.
- Gonzalez, A. M., Hoffman, J. R., Townsend, J. R., Jajtner, A. R., Boone, C. H., Beyer, K. S., Baker, K. M., Wells, A.J., Mangine, G. T., & Robinson, E. H. (2016). Intramuscular MAPK signaling following high volume and high intensity resistance exercise protocols in trained men. European Journal of Applied Physiology, 116, 1663-1670.
- Gonzalez, A. M., Sell, K. M., Ghigiarelli, J. J., Kelly, C. F., Shone, E. W., Accetta, M. R., Baum, J. B., & Mangine, G. T. (2017). Effects of phosphatidic acid supplementation on muscle thickness and strength in resistance-trained men. Applied Physiology, Nutrition, and Metabolism, 42, 443-448.
- Gonzalez, A. M., Spitz, R. W., Ghigiarelli, J. J., Sell, K. M., & Mangine, G. T. (2017, e-published ahead of print). Acute effect of citrulline malate supplementation on upper-body resistance exercise performance in recreationally resistance-trained men. Journal of Strength and Conditioning Research.
- Mangine, G. T., Hoffman, J. R., Gonzalez, A. M., Townsend, J. R., Wells, A. J., Jajtner, A. R., Beyer, K. S., Boone, C. H., Miramonti, A. A., & Wang, R. (2015). The effect of training volume and intensity on improvements in muscular strength and size in resistance trained men. Physiological Reports, 3, e12472.
- Silva, V. R., Belozo, F. L., Micheletti, T. O., Conrado, M., Stout, J. R., Pimentel, G.D., & Gonzalez, A. M. (2017). ß-Hydroxy-ß-methylbutyrate free acid supplementation may improve recovery and muscle adaptations after resistance training: A systematic review. Nutrition Research, 45, 1-9.