All muscle contractions are equally important for muscle growth. Overloading the eccentric component results in more muscle damage and soreness at first. The muscle then protects itself from further damage through the repeated bout effect. After that, muscle damage and soreness are diminished. If you incorporate heavy eccentric exercise into your routine, you will probably need to reduce your workout frequency to accommodate the excess muscle damage and soreness.
CONCENTRIC VS ECCENTRIC EXERCISE FOR GAINING MUSCLE SUMMARY
- There is no superiority of eccentric exercise compared to concentric contractions when high levels of effort or the sets are taken to failure.·
- Muscle damage becomes less over time due to the repeated bout effect, but muscle growth still occurs.
- Excess muscle damage can reduce muscle growth.
- When using the same amount of weight, concentric contractions (lifting the weight) are highly fatiguing, whereas eccentric contractions (lowering the weight) are relatively fatigue-resistant.
- Muscle growth can occur with both heavy and light weight, independent of the load.
THE TYPES OF CONTRACTIONS THAT CAN INFLUENCE MUSCLE GROWTH: CONCENTRIC VS ECCENTRIC EXERCISE
Repetitions are further broken down into three components: a concentric phase (concentric meaning lifting the weight), an isometric phase (muscle contracting, but no joint movement is occurring), and an eccentric phase (eccentric meaning lowering the weight). The difference between concentric and eccentric exercises is during the concentric phase, the muscle shorts, whereas during the eccentric phase, the muscle is lengthened or stretched.
If you were using the leg extension, the lift would begin with a concentric phase in which the weight is lifted. The isometric phase is when the weight is paused in the middle of the movement, and finally, the eccentric phase is when the weight is lowered.
Contracting (concentric) and stretching (eccentric) muscles are crucial for muscle growth. Contrary to belief, isometric training (no movement) can increase muscle growth.[14]
Isometric exercise places tension on the muscle, but the active contracting and stretching of muscle results in superior muscle growth. It’s not uncommon to see people in the gym lifting a weight with no control; however, it’s important to understand that tension and tension duration on the muscle are much more important than the weight.
ECCENTRIC EXERCISE
This means that a maximal lift lasting a few seconds will be inferior to muscle growth using a lesser weight but more tension on a muscle over a longer duration. Researchers found that when subjects trained with 75% of a maximal voluntary contraction, sustained muscle contractions in the leg extension (contracted the legs explosively for 1 sec but held the contraction for 3 seconds) resulted in more than a 3-fold greater increase in muscle growth than explosive contractions (contracting as hard and as fast as possible).[15] This shows that muscle growth depends on the weight and loading duration (i.e., time).
This simple study is a good analogy for muscle growth responses between powerlifting and bodybuilding protocols. Powerlifting protocols use peak tension for a short time frame, whereas bodybuilding protocols result in greater sustained tension for a more prolonged period.
Isometric exercise places tension on the muscle, but no active stretch will result in lesser muscle growth than actively contracting the muscle.[16] You expose different muscle fibers to various external stressors by actively stretching and contracting the muscle.
IS ECCENTRIC OVERLOAD THE BEST EXERCISE FOR MUSCLE GROWTH?
Many have suggested that heavy eccentric exercises or negative reps increase strength and muscle size more effectively. Eccentric strength (i.e., lowering the weight) is about 20–40% greater than concentric strength (lifting the weight), so naturally, this results in greater tension overload for the eccentric portion. It’s not uncommon to see resistance bands eccentric loading techniques being used to maximize eccentric loading.
THE BENEFITS OF ECCENTRIC EXERCISE FOR MUSCLE GROWTH
In studies that compare eccentric exercise to concentric exercise, there is greater muscle growth from eccentric exercise (10%) than concentric exercise (6.8%) due to a greater tension placed on the muscle through an eccentric contraction.[1]
Remember, you can handle a greater weight by lowering the weight than lifting. There is also evidence of greater type II muscle fiber growth during eccentric overloading exercises. One of the most impressive studies comparing traditional exercise to accentuated eccentric loading was a study performed on hockey players, which found that eccentric overload resulted in an 8.9% increase in quad muscle growth. In contrast, the traditional resistance exercise group gained 2.1%.[2]
ECCENTRIC EXERCISE EXAMPLES
Most gyms don’t have accentuated eccentric overload machines, so lifters often create their own methods of eccentric overload. The most common method is lifting with two arms and lowering with one arm (i.e., pulling down with a v bar handle with both hands and slowly lowering the weight with one arm). The same concept can be used with the legs, where you lift the weight with both legs and lower with one leg. Eccentric overload has been suggested to be a superior way of gaining muscle because of the greater tension overload; more muscle growth can occur.
CONCENTRIC HYPERTROPHY VS ECCENTRIC HYPERTROPHY
Some, but not all, studies have found that eccentric overload will increase muscle growth. Some studies have found that muscle growth is similar despite using an eccentric overload.
One study found that the eccentric overload group had greater strength gains than traditional resistance exercise; however, muscle growth increased similarly in both groups, despite the concentric/eccentric overload group using a 40% greater workload on the eccentric component.[3]
The concentric training volume was similar for both groups, but the total training volume was greater for the eccentric overload group because they used a heavier eccentric contraction.
It was also stated that once they reached muscular failure in the traditional training group, the load was reduced the next set. So based on this, the traditional training group was training with failure during some sets and used a high level of effort. So how can you use a heavier eccentric load and muscle contractions and not produce more muscle growth?
ECCENTRIC OVERLOADING TRAINING
Muscle hypertrophy is more about a high level of effort or high exertion levels than the actual weight used. [4,5] Effort levels determine how much muscle activation is occurring and the level of motor unit recruitment.
Studies have found that both heavy and light weights can cause similar levels of muscle growth when trained to failure. Suppose the traditional exercise group is training to failure. In that case, full muscle activation is occurring, which could be why the traditional training group gained a similar amount of muscle despite using a lighter weight for the eccentric component. Similar to the studies showing equal muscle growth with heavier and light weight exercise taken to failure.
Another study had subjects perform one leg using concentric and the other leg using eccentric contractions of the quadriceps muscle for 20 weeks.
The eccentric contractions used a 35% higher loading regimen than the concentric training routine. Despite the higher loading of eccentric contractions, the groups’ muscle growth was the same.[6]
The last study to be discussed had subjects train one leg with concentric contractions (80% 1-RM, 2 – 3 s per repetition) and the other leg with eccentric contractions (145% 1-RM, 2 – 3 s per repetition) on a leg extension machine. Both groups had similar increases in muscle mass.[7]
ECCENTRIC VS CONCENTRIC CONTRACTIONS PERFORMED WITH THE SAME WEIGHT
What if you equate the concentric and eccentric workloads, so they were equal? One study measured arm size and strength changes in response to groups that used a normal concentric contraction with an eccentric overload compared to a traditional resistance exercise program.
Because eccentric overload uses a heavier weight, the researchers had the subjects in the traditional exercise group do an added set to create an even total workload.
The regular training groups did 4 sets of 75% of a 1 RM with concentric and eccentric contractions. The eccentric overload group did 3 sets of 75% a concentric 1RM and eccentric contractions with 120% of 1RM. There was no difference in muscle growth even though both groups increased muscle strength at the end of the study.[8]
The author suggested that the lack of changes in muscle could have been because of the advanced training status of the subjects, or longer than 9 weeks of training could have resulted in changes in muscle size. A review on accentuated eccentric overloading suggested that changes in muscle size from accentuated eccentric loading may take longer than 12 weeks, as many of the studies so far have been less than 12 weeks.[9]
ECCENTRIC EXERCISE CAUSE MORE MUSCLE DAMAGE AT FIRST
Another study had subjects use 5 sets of eccentric exercises with 110% of their 1-RM. The researchers measured the biceps circumference with MRI imaging. After the intense eccentric exercise, the subjects experienced soreness and elevated markers of muscle damage. Still, the most shocking finding was that arm volume or size decreased on three separate occasions at weeks 2, 3, and 8 weeks after exercise.
The authors suspected the loss of arm volume was due to intense damage caused by eccentric exercise.[10] Again, this points to extreme muscle damage that can result in impaired muscle gains in the early phases of exercise, with muscle damage exceeding the body’s ability to recuperate and grow.
However, the repeated bout effect makes the body more resilient to muscle damage. Also, remember that heavy eccentric exercise that causes muscle damage will reduce the muscle’s ability to store glycogen.[11] Thus, athletes will have impaired recuperation following intense eccentric exercise.
CONCENTRIC HYPERTROPHY VS ECCENTRIC HYPERTROPHY
It’s important to note that concentric and eccentric muscle contractions result in different types of muscle growth achieved through contraction-specific modalities.
The concentric portion or muscle shortening will increase muscle size diameter or cross-sectional area. Eccentric stretching contractions cause an increase in muscle growth by increasing fascicle length.[12]
Studies have found that eccentric-only contractions cause muscle growth at the distal or furthest end of the muscle, whereas concentric contractions cause muscle growth in the middle region.[13] This suggests that you need a combination of concentric and eccentric exercises for maximal muscle growth because each contraction causes different types of muscle growth.
Just remember, how much damage you occur during exercise will determine when you can retrain that muscle, so if you are planning to add some eccentric overload partner-assisted contractions, plan for increased recovery time.
SUMMARY
All muscle contractions are equally important for muscle growth. Overloading the eccentric component results in more muscle damage and soreness at first. The muscle then protects itself from further damage through the repeated bout effect. After that, muscle damage and soreness are diminished. If you incorporate heavy eccentric exercise into your routine, you will probably need to reduce your workout frequency to accommodate the excess muscle damage and soreness.
ECCENTRIC EXERCISE KEY POINTS
- Muscle damage becomes less over time due to the repeated bout effect, but muscle growth still occurs.
- Excess muscle damage can reduce muscle growth.
- Muscle growth can occur with both heavy and light weight, independent of the load.
REFERENCES
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