Hypertrophy – training periodization part III

The training periodization of an athlete’s annual program includes meticulously planned phases aimed at increasing the athlete’s performance. In the last article we discussed the beginning of the preparatory phase and its first macrocycle – anatomical adaptation. This time we will focus on the second step which is muscular hypertrophy.

Strength vs. size

Many people think that the bigger a person is, the higher level of strength they possess. This is not always the case. For example, a weight lifter may be able to lift a much heavier weight than his bulkier bodybuilder friend. These two individuals have 2 different goals. For this reason, the athlete and their coach should aim to increase the “dry muscle mass” that is functional for their sport. Special attention should be given to hypertrophy of fast type II muscle fibers that contribute to increased strength expression. 

Bodybuilding training vs. athletic training

As you may have guessed, bodybuilder and athlete training must differ significantly, just as physique-oriented hypertrophy and sport-specific hypertrophy differ. Bodybuilders and in hypertrophy training typically use weights between 60% and 80% of maximum weight in a range of 8 to 15 series, each of which is carried almost to the point of total muscle fatigue and collapse. However, some bodybuilders owe their success to training with fewer repetitions and heavy weights while performing forced repetitions and negative repetitions. Others achieve very good results by performing a high number of repetitions (up to 20) to failure. As we can guess, in professional figure sports it’s not just the training that makes the difference. 

What is muscular hypertrophy

Hypertrophy is a term that means the growth and increase in size of muscle cells without an increase in the number of muscle cells (hyperplasia). When you start exercising your muscles, there is first an increase in the frequency of nerve impulses sent that cause the muscles to contract. Over time, more pathways (neuromuscular connections) are created by which these impulses reach the muscles and the efficiency of their activation increases. This alone often results in an increase in strength without a noticeable change in muscle size. As exercise continues, a complex interaction of nervous and endocrine system responses occurs that results in increased protein synthesis. Over the course of months, muscle cells become larger and stronger. 

There are 2 basic types of muscle hypertrophy: sarcoplasmic hypertrophy and myofibrillar hypertrophy.

1. Sarcoplasmic hypertrophy (non-functional) 

Sarcoplasmic hypertrophy is characterized by an increase in the volume of sarcoplasmic fluid in a muscle cell, without an actual increase in muscle strength. Think “pump.” This type of hypertrophy is what bodybuilders typically focus on when maximizing their overall muscle size. The sarcoplasm is actually the fluid and energy stores surrounding the myofibrils in your muscles. This fluid contains ATP molecules, glycogen, creatine phosphate and water. 

With sarcoplasmic hypertrophy, muscles adapt to last longer (work) with less need for maximum force and speed of contraction. This increases muscle size but does not increase muscle fibers, resulting in less functional mass and decreased relative strength (force per kilogram of body weight).

Typical parameters for sarcoplasmic hypertrophy training:

8-12 repetitions (40-70 sec under tension)

3-7 series

60-120 sec interval between series 

2. Myofibrillar hypertrophy (functional)

Myofibrillar hypertrophy refers to the growth of muscle fibers. It results in an increase in contractile proteins (actin and myosin) in muscle cells. Instead of swelling and increased cell volume, there is an increase in cell density. This results in an increase in actual muscle strength, while size does not change as drastically as with sarcoplasmic hypertrophy. 

Typical parameters for sarcoplasmic hypertrophy training:

6-8 repetitions (20-40 seconds under tension)

4-6 series

90-180 sec interval between sets

Research points to 3 main factors that stimulate hypertrophy and muscle growth:

• Mechanical tension (muscle tension)
• Muscle damage (microtrauma)
• Metabolic stress

1. Muscle tension 

One of the determinants of muscle growth is tension. Tension comes from overload. When you subject a muscle to more overload than it is used to, it sends a signal to cells called satellite cells. Once signaled, these satellite cells begin to multiply and fuse with existing muscle fibers to form new contractile proteins. The increase in contractile proteins makes each muscle fiber larger and the muscles stronger and more defined.

Where does this muscle tension come from? We create it during the concentric phase of movement, when we tighten or shorten our muscles during strength training, and during the eccentric phase, when you lengthen your muscles in a controlled manner. When we lower the weight, the muscles maintain tension to resist gravity. Both the concentric and eccentric phases of muscle contraction create tension. However, it is actually the eccentric portion of the movement that creates more tension on the muscle than the concentric or shortening phase.

When you lift more weight or apply more resistance, you expose your muscles to more tension than when you lift lighter weights. So, high resistance means more tension and stress in the muscles you are working on. To stimulate muscle growth, you need a certain level of tension, at least 65% of the maximum of one repetition. Some research suggests that lifting lighter weights with a high number of repetitions to failure also puts enough stress on the muscles to stimulate growth.

Muscle tension is one factor that promotes muscle hypertrophy, but not the only one. If muscle tension were the only stimulus for muscle growth, triathletes would have bigger muscles than bodybuilders because of the weights they lift (bigger weights cause more muscle tension). In most cases, bodybuilders have more muscle hypertrophy than power triathletes.

2. Muscle damage

Another factor that stimulates satellite cells (muscle tissue stem cells) and causes them to form larger fibers is muscle damage. Strength training causes microscopic cracks in muscle fibers. This causes a brief inflammatory response during which white blood cells (M1 macrophages) move into the area to remove the damaged tissue (phagocytosis). The inflammatory process that occurs as a result of damage to the muscle fibers is what we experience in pain commonly referred to as “soreness”.

On the second day after the injury, M2c macrophages, which secrete anti-inflammatory substances, begin to participate in the reaction. This group of macrophages begins the process of regeneration of the damaged tissue by secreting growth factors (e.g. TGF-β) and stimulates the activation and proliferation (increase in number) of satellite cells. As a result of satellite cell differentiation, protein expression increases and new muscle cells are formed. 

It is believed that muscle growth is possible without muscle damage. If you think about it, your muscles continue to grow even if you don’t feel pain after a workout. For this reason, muscle damage may not be a sufficient condition for hypertrophy.

3. Metabolic stress

Why do bodybuilders see more muscle growth than triathletes even though they lift heavier weights? Triathletes lift very heavy weights but perform a small number of repetitions because their main goal is to build strength. Bodybuilders lift lighter weights, thus exposing their muscles to less stress, but perform more repetitions and series.

The result of resistance training is metabolic stress, which is the accumulation of lactic acid, inorganic phosphate (Pi) and hydrogen ions H+ in the cell. The accumulation of these compounds causes:

– release of growth hormones 

– hypoxia

– production of reactive oxygen species (ROS)

– swelling of the cell

Cell swelling and metabolite accumulation promotes muscle growth. Variations in training parameters such as intensity, volume, and rest between series are determinants of the amount of metabolic stress. Furthermore, different types of training, such as low-intensity strength training (70%1RM), blood flow restriction, and high-intensity interval training, can be used to maximize metabolic stress. Some studies suggest that metabolic stress may be more important than muscle tension for stimulating muscle hypertrophy.

Hypertrophy – maximization

In order to maximize muscle growth, there must be a balance between tension and metabolic stress. When training with a high load >85%1RM we are only able to perform a few repetitions. While this is great for increasing muscle tone and strength, the number of repetitions may not be enough to cause metabolic stress.  

Research shows that performing a moderate number of repetitions as opposed to fewer repetitions maximizes the release of anabolic hormones such as testosterone and growth hormone (Rietjens 2014). In addition, increasing total volume maximizes the release of growth hormone (Gotshalk et al. 1997).

Another way to manipulate muscle tension and metabolic stress is to manipulate the rest interval between series. A long rest period (2 to 3 minutes) maximizes muscle recovery so that we are able to lift heavy weights. Long rest periods are ideal for strength building but not hypertrophy because metabolic stress is minimal at that time. Moderate rest periods (60 to 90 seconds) cause more metabolic stress and still allow us to use a weight heavy enough to exert adequate tension on the muscles.

Additional factors affecting hypertrophy:

Nutrition 

Complete meals that contain protein, carbohydrates, and unsaturated fats will promote the process of muscle fiber growth. Also important is the form and time of their intake. To optimize hypertrophy, the following intake is recommended: 1.8-2g of protein/kg body weight, 5-7g of carbohydrates/kg body weight, and about 25-30% of fats from your daily energy requirements. Remember that meals and the exact amount of calories should be determined individually.

Specific training methods 

This is the way of performing exercises and managing its parameters. Some of the most effective hypertrophy methods are: repetition method, quantitative and mechanical drop series method, cluster series method, 1&1/2 method, forced repetitions, occlusion training. 

Supplementation 

Most hypertrophy supplements are designed for advanced individuals and bodybuilders. One of the most popular supplements for muscle hypertrophy is creatine.

Hypertrophy in sport

Athletes and coaches must be careful when introducing hypertrophy training into an annual training plan. It is especially important to be specific about the needs of the individual athlete and the amount of time that will be devoted to hypertrophy. Sarcoplasmic hypertrophy is not useful in most sports (with some exceptions like American soccer). Therefore, it should be right at the beginning of the preparation period, if at all. At that point, training should consist of multi-joint exercises that engage the major muscle groups responsible for athletic performance. The hypertrophy phase can last from 4 to 8 weeks depending on the needs of the athlete and the type of sport. For athletes who need additional muscle mass, this phase can be longer and recur throughout the year. 

Summary

Hypertrophy-oriented training increases muscle cell size. Training with a relatively low load <70%1RM and a rep range of 8-12 will result in increased muscle volume without a large increase in strength or speed of development. In contrast, a load >75%1RM and a repetition range of 6-8 will influence myofibrillar growth and increase muscle cell density while increasing strength. Hypertrophy is influenced by 3 main factors: tension, muscle damage, and metabolic stress. The coach and athlete must determine the appropriate type of hypertrophy to suit the needs of the athlete and the sport, and then select specific training methods. 

References:

1. Freitas M, et al, (2017), Role of metabolic stress for enhancing muscle adaptations: Practical applications, “World Journal of Methodology”, Jun 26; 7(2): 46-54

2. Villanueva MG, (2015), Influence of Rest Interval Length on Acute Testosterone and Cortisol Responses to Volume-Load Equated Total Body Hypertrophic and Strength Protocols, “Journal of Strength and Conditioning Research”, Oct; 26(10): 2755-2764.

2. Rietjens R, (2014), Acute T Acute Testosterone Responses t one Responses to Different Resistance Ex ent Exercise Intensities, UNLV Theses, Dissertations, Professional Papers, and Capstones, 2209. 

3. Ahtiainen J, et al. (2003), Muscle hypertrophy, hormonal adaptations and strength development during strength training in strength-trained and untrained men, European journal of applied physiology, 89(6), 555-563.

4 Gotshalk L, Loebel C. C., Nindl B. C., Putukian M., Sebastianelli W. J., Newton, R. U., Kraemer W. J, (1997), Hormonal responses of multiset versus single-set heavy-resistance exercise protocols, “Canadian Journal of Applied Physiology”, 22(3), 244-255.