×

Bundle & Save

Shop Now

Muscle Mass

Muscle Mass

Stimulating Muscle Growth


The conquest for bigger and leaner muscle leaves many scouring the internet looking up what the best way is to build muscle as well as muscle gain workouts. Search results turn-up things like high-intensity heavy resistance training, low-load and high-volume training [1], and an assortment of many other popular strength and conditioning programs aimed at promoting muscle hypertrophy. Muscle hypertrophy is simply muscle growth. At a cellular level, the mechanisms of skeletal muscle hypertrophy encompass a combination of muscle fiber repair and the signalling of cellular hypertrophic pathways which both ultimately contribute to bigger muscles [2,3]. Though, a commonly overlooked modality that may be essential to optimizing muscle hypertrophy is electric muscle stimulation. Through Smart Neuromuscular Electrical Stimulation (NMES), PowerDot has optimized the technology of electrical muscle stimulation to promote further gains in muscle hypertrophy. 


Interestingly enough, muscle hypertrophy is not a component of muscular fitness. Muscular fitness consists of three factors: endurance, power, and strength [4]. Muscular endurance is the muscle’s ability to maintain repeated contractions over a period of time [4]. Muscular power is the ability of the muscle to contract forcefully and quickly [4]. Lastly, muscular strength is simply the generation of force by the skeletal muscle [4]. Though not a component of muscular fitness, it is well accepted that bigger muscle is generally stronger muscle [5] making muscle size an important component of muscle quality. Muscle quality quantifies the relationship of skeletal muscle strength to muscle mass [6]. A decrease in muscle size may lead to an even greater decrease in muscular strength resulting in poor muscle quality causing a decline in physical function and early mortality [7].


PowerDot Smart NMES technology may be the key to maximize muscle hypertrophy. Through technological advancements, PowerDot ingenuity has revolutionized the previously archaic modality device of muscle electrical stimulation. What used to consist of clunky machines, tangled wires, and unknown program settings, is now controlled via bluetooth through an app on a phone or tablet with several scientifically designed preset programs. Powerdot’s innovation of the first FDA approved app-based NMES unit, provides the highest standard of performance. 


Muscle stimulation devices have been disregarded when it comes to promoting muscular hypertrophy. These devices are generally looked at for recovery or maybe to increase strength. However, electrical stimulation may be the most important piece of technology when it comes to promoting muscular hypertrophy. Electric muscle stimulation upregulates key anabolic hypertrophy signalling pathways, and by stimulating both muscle fiber types (Type I and Type II), it maximizes hypertrophic adaptations more so than other strength and conditioning protocols alone [8,9]. If aiming to promote muscle hypertrophy, PowerDot technology is of paramount importance and should be implemented in all training programs. 


Physiological Mechanisms of Muscle Hypertrophy


Muscle is a post-mitotic tissue. Meaning, skeletal muscle fibers (muscle cells) do not undergo mitosis (cell division) after fetal development is complete [2]. Mitosis is the process of cellular division and replication of cells. Essentially, replacing old worn out cells with new and improved cells. However, muscle cells do not undergo mitosis (hence, post-mitotic) which is why it is imperative to have an effective means of muscle cell repair to prevent muscle cell death. This allows for the maintenance and/or increases of skeletal muscle mass [2]. 


Resistance training for hypertrophy may result in muscular damage, which ultimately requires repair of the damaged muscle tissue. Though findings suggest that hypertrophy may be possible without muscle damage [3], exercise induced muscle damage (EIMD), may be the most effective means to increase skeletal muscle hypertrophy. As previously mentioned, a combination of muscle fiber repair and the activation of  cellular signalling hypertrophic pathways consequently results in muscle growth. With EIMD, muscle hypertrophy is increased due to a gradual accumulation of muscle proteins through the upregulation of the IGF-1 system, release of inflammatory agents, and activation of satellite cells [3]


During and post-exercise, IGF-1 levels increase as growth hormone is released. IGF-1 is a hormone that is upregulated with skeletal muscle contraction and stimulates myogenic hypertrophy signalling pathways (ie. PI3K/mTOR and MAPK) that promote muscle protein synthesis [2]. Protein synthesis is the process of making proteins… and it’s these proteins that perform the functions of the cell. In this case, the body is making more skeletal muscle proteins, and with more proteins packed into the cell, the muscle cell becomes bigger. Now, with cellular stress, like the mechanical stress placed on the muscle during exercise, the PI3K/mTOR and MAPK pathways will activate downstream agents that increase muscle protein synthesis as well as promote growth and differentiation of the muscle cells [10]. By increasing the size of each cell, the entire muscle as a whole will display an increase in cross-sectional area.


The aftermath of an exhaustive training session results in skeletal muscle damage (EIMD). As a result of the damage, the cell must repair itself, and any repair process begins with inflammation. First to the site of damage are macrophages and neutrophils. Both are phagolytic cells that clean up cellular debris in the damaged area. Macrophages release cytokines (proteins involved in cell signalling) which significantly contribute to the hypertrophic response [11,12]. Neutrophils may enhance hypertrophic effect through the production of reactive oxygen species (ROS). ROS usually have a negative connotation, however, ROS may promote hypertrophic effects by increasing MAPK activation via enhanced IGF-1 signaling [13,14]. 


Lastly, muscle hypertrophy is thought to be mediated by the activity of satellite cells. Satellite cells are myogenic stem cells located in the skeletal muscle that remain inactive until sufficient stress is placed on the skeletal muscle… like during high-intensity muscular contractions [15,16,17]. Once activated, satellite cells fuse to existing damaged muscle cells and repair the injured tissue [18]. It is also important to note that satellite cells also coexpress various myogenic regulatory factors [19], and it’s this combination that aids in muscle repair, regeneration, and growth.

Exercise Induced Muscle Hypertrophy


When designing a strength and conditioning program, or a muscle gain workout plan, it is important to keep three things in mind: exercise order, load/intensity, and volume. Exercise order, focused on proper order of muscle workout groups, is important as there may not only be physiological benefits but there is a safety component as well. Exercise intensity and volume are highly debated topics and it is believed that high-intensity resistance training is needed to optimize hypertrophy. However, new research is indicating that lower intensity, or lower load training, may be able to stimulate similar if not greater hypertrophic results [1]. Though this lower load training may be great for maximizing hypertrophy while decreasing stress placed on the joints, a greater amount of exercise volume may be needed. Exercise order, intensity, and volume are staples when designing a high-quality resistance training program.


It cannot be stressed enough, the importance of exercise order when designing an effective strength and conditioning program. Exercises should be performed in the following order: Power, Core, and Accessory. Power exercises consist of Olympic Weightlifting movements, like the snatch and clean, as well as plyometric exercises. The reason these exercises go first is that they are highly complex multi-joint movements. Performing other exercises first may result in fatigue and compromised form, thus increasing injury risk. Core exercises are next, and these are not abdominal exercises. Core exercises are main lifts, like the squat and deadlift, or the leg press for machine exercises. Core exercises are focused on multiple joints and muscle groups that require bracing of the core. Lastly, accessory or assistant exercises are performed, which are generally single joint exercises. The focus is on single muscle groups that will contribute to the power and core lifts. These are performed last since there is a decreased risk of injury as these exercises are less complex and performed with lighter weights.


But, what about hypertrophy and exercise order? It has been theorized that performing larger muscle group exercises first stimulates greater muscular hypertrophy due to increased endogenous levels of anabolic hormones like testosterone. However, research has demonstrated that there may be a negligible relationship between acute endogenous hormone production and muscle hypertrophy [20]. For the reasons above, it’s important to focus on multi-joint big muscle groups followed by single joint exercises.


The goals of a training program are going to influence the intensity and volume of the training period. Think, higher intensity = high weight, high volume = high repetitions. Interestingly enough, findings indicate that both high-intensity and low-intensity with high volume resistance training elicits similar and significant increases in muscle hypertrophy [1]. This demonstrates that volume may be the primary driver of muscle growth [21]. This goes back to exercise order as performing the barbell back squat first in an exercise session allowed for the completion of more total repetitions (ie. more volume) [22]. 


Though, it may be possible to still lift lighter (low intensity) with less repetitions (lower volume) and still elicit significant improvements in muscle hypertrophy. Blood flow restriction (BFR) training is a type of low load resistance training that consists of occluding arteries to restrict blood flow to the skeletal muscle. This is generally performed at approximately 30% max intensities and exercise volume stays the same [23]. Using lower loads decreases the amount of stress placed on the bodily joints while still stimulating hypertrophic adaptations and muscle growth that are similar to high-intensity training [23]. 


PowerDot Smart NMES Optimizes Muscle Growth


Though exercise order, intensity, and volume are important when trying to maximize muscle hypertrophy, PowerDot NMES technology has the capacity to further enhance hypertrophic effects with training. NMES is generally used to focus on strength gains. 

Stimulating one leg with NMES during 6-weeks of training and using the other leg as a control, scientists revealed that the leg that received NMES increased in strength by 24% and the control leg by only 10% [24]. Electrical muscle stimulation has also demonstrated to increase an Elite Weightlifters front squat by 20 kg within one week [25]. However, most notably from this case study was that NMES resulted in muscle fiber size increases (ie. muscle hypertrophy) [25].


NMES takes a “nonselective approach”, activating both fiber types at the same time [26] and there are several means by which PowerDot Smart NMES technology may be used to increase muscle mass. Though there is a dose response relationship between NMES intensity and hypertrophy, even low intensity NMES has demonstrated to increase muscle fiber cross-sectional area [9]. By implementing NMES, researchers have demonstrated an increase in muscle cross-sectional area by up to 11% [27]. The cause behind the increase in muscle size and strength may be due to both low and high-frequency NMES upregulating the key hypertrophic anabolic signaling pathways mentioned earlier [8]. This is clearly evident when NMES is used in conjunction with BFR training. Low-intensity NMES-BFR induced greater muscle hypertrophy, compared to just NMES and BFR alone, through the upregulation of the mTOR and MAPK signaling pathways [28,29]. 


PowerDot now makes it easier than ever to build muscle at home with any at home workout. Typical NMES resistance exercises are performed under isometric conditions which is a recommended starting point. So, when using a hypertrophy protocol, every time there is an electrical stimulus, users should “flex” the muscles that the pads are placed on. Over time, users may progress and move to using electrical stimulation during only the eccentric/concentric phases of an exercise and eventually moving to both eccentric/concentric phases. Adding NMES as a separate session in conjunction with other resistance training programs adds extra volume and optimizes hypertrophic gains. Pick-up the PowerDot Duo 2.0 and get the most out of your training.

 

References

  1. Schoenfeld, B. J., Peterson, M. D., Ogborn, D., Contreras, B., & Sonmez, G. T. (2015). Effects of low-vs. high-load resistance training on muscle strength and hypertrophy in well-trained men. The Journal of Strength & Conditioning Research29(10), 2954-2963. [Link]
  2. Schoenfeld, B. J. (2010). The mechanisms of muscle hypertrophy and their application to resistance training. The Journal of Strength & Conditioning Research24(10), 2857-2872. [Link]
  3. Schoenfeld, B. J. (2012). Does exercise-induced muscle damage play a role in skeletal muscle hypertrophy?. The Journal of Strength & Conditioning Research26(5), 1441-1453. [Link]
  4. Ruiz, J. R., Castro-Piñero, J., Artero, E. G., Ortega, F. B., Sjöström, M., Suni, J., & Castillo, M. J. (2009). Predictive validity of health-related fitness in youth: a systematic review. British Journal of Sports Medicine43(12), 909-923. [Link]
  5. Taber, C. B., Vigotsky, A., Nuckols, G., & Haun, C. T. (2019). Exercise-induced myofibrillar hypertrophy is a contributory cause of gains in muscle strength. Sports Medicine49(7), 993-997. [Link]
  6. Schroeder, E. Todd, Michael Terk, and Fred R. Sattler. "Androgen therapy improves muscle mass and strength but not muscle quality: results from two studies." American Journal of Physiology-Endocrinology and Metabolism 285.1 (2003): E16-E24. [Link]
  7. Brown, J. C., Harhay, M. O., & Harhay, M. N. (2016). The muscle quality index and mortality among males and females. Annals of Epidemiology26(9), 648-653. [Link]
  8. Mettler, J., Magee, D., & Doucet, B. (2018). High-frequency neuromuscular electrical stimulation increases anabolic signaling. Medicine & Science in Sports & Exercise50(8), 1540-1548. [Link]
  9. Natsume, T., Ozaki, H., Kakigi, R., Kobayashi, H., & Naito, H. (2018). Effects of training intensity in electromyostimulation on human skeletal muscle. European Journal of Applied Physiology118(7), 1339-1347. [Link]
  10. Roux, P. P., & Blenis, J. (2004). ERK and p38 MAPK-activated protein kinases: a family of protein kinases with diverse biological functions. Microbiology and Molecular Biology Reviews68(2), 320-344. [Link]
  11. Quinn, L. S. (2008). Interleukin-15: a muscle-derived cytokine regulating fat-to-lean body composition. Journal of Animal Science86(suppl_14), E75-E83. [Link]
  12. Nielsen, A. R., & Pedersen, B. K. (2007). The biological roles of exercise-induced cytokines: IL-6, IL-8, and IL-15. Applied Physiology, Nutrition, and Metabolism32(5), 833-839. [Link]
  13. Takarada, Y., Nakamura, Y., Aruga, S., Onda, T., Miyazaki, S., & Ishii, N. (2000). Rapid increase in plasma growth hormone after low-intensity resistance exercise with vascular occlusion. Journal of Applied Physiology88(1), 61-65. [Link]
  14. MacNeil, L. G., Melov, S., Hubbard, A. E., Baker, S. K., & Tarnopolsky, M. A. (2010). Eccentric exercise activates novel transcriptional regulation of hypertrophic signaling pathways not affected by hormone changes. PloS One5(5), e10695. [Link]
  15. Hawke, T. J., & Garry, D. J. (2001). Myogenic satellite cells: physiology to molecular biology. Journal of Applied Physiology[Link]
  16. Rosenblatt, J. D., Yong, D., & Parry, D. J. (1994). Satellite cell activity is required for hypertrophy of overloaded adult rat muscle. Muscle & Nerve17(6), 608-613. [Link]
  17. Vierck, J., O'Reilly, B., Hossner, K., Antonio, J., Byrne, K., Bucci, L., & Dodson, M. (2000). Satellite cell regulation following myotrauma caused by resistance exercise. Cell Biology International24(5), 263-272. [Link]
  18. Toigo, M., & Boutellier, U. (2006). New fundamental resistance exercise determinants of molecular and cellular muscle adaptations. European Journal of Applied Physiology97(6), 643-663. [Link]
  19. Cornelison, D. D. W., & Wold, B. J. (1997). Single-cell analysis of regulatory gene expression in quiescent and activated mouse skeletal muscle satellite cells. Developmental Biology191(2), 270-283. [Link]
  20. Fink, J., Schoenfeld, B. J., & Nakazato, K. (2018). The role of hormones in muscle hypertrophy. The Physician and Sportsmedicine46(1), 129-134. [Link]
  21. Schoenfeld, B., & Grgic, J. (2018). Evidence-based guidelines for resistance training volume to maximize muscle hypertrophy. Strength & Conditioning Journal40(4), 107-112. [Link]
  22. Spreuwenberg, L. P., Kraemer, W. J., Spiering, B. A., Volek, J. S., Hatfield, D. L., Silvestre, R., ... & Maresh, C. M. (2006). Influence of exercise order in a resistance-training exercise session. The Journal of Strength & Conditioning Research20(1), 141-144. [Link]
  23. Lowery, R. P., Joy, J. M., Loenneke, J. P., de Souza, E. O., Machado, M., Dudeck, J. E., & Wilson, J. M. (2014). Practical blood flow restriction training increases muscle hypertrophy during a periodized resistance training programme. Clinical Physiology and Functional Imaging34(4), 317-321. [Link]
  24. Balogun, J. A., Onilari, O. O., Akeju, O. A., & Marzouk, D. K. (1993). High voltage electrical stimulation in the augmentation of muscle strength: effects of pulse frequency. Archives of Physical Medicine and Rehabilitation74(9), 910-916. [Link]
  25. Delitto, A., Brown, M., Strube, M. J., Rose, S. J., & Lehman, R. C. (1989). Electrical stimulation of quadriceps femoris in an elite weight lifter: a single subject experiment. International Journal of Sports Medicine10(03), 187-191. [Link]
  26. Bickel, C. S., Gregory, C. M., & Dean, J. C. (2011). Motor unit recruitment during neuromuscular electrical stimulation: a critical appraisal. European Journal of Applied Physiology111(10), 2399. [Link]
  27. Jandova, T., Narici, M. V., Steffl, M., Bondi, D., D’Amico, M., Pavlu, D., ... & Pietrangelo, T. (2020). Muscle Hypertrophy and Architectural Changes in Response to Eight-Week Neuromuscular Electrical Stimulation Training in Healthy Older People. Life10(9), 184. [Link]
  28. Natsume, T., Ozaki, H., Saito, A. I., Abe, T., & Naito, H. (2015). Effects of electrostimulation with blood flow restriction on muscle size and strength. Medicine and Science in Sports and Exercise47(12), 2621-2627. [Link]  #2
  29. Natsume, T., Yoshihara, T., & Naito, H. (2019). Electromyostimulation with blood flow restriction enhances activation of mTOR and MAPK signaling pathways in rat gastrocnemius muscles. Applied Physiology, Nutrition, and Metabolism44(6), 637-644. [Link]  #3

Ready to take the next step? Explore more below

Strength

Jan 25

Mobility

Jan 25