Chapter 1: Understanding Resistance Training

Athletes consistently seek ways to enhance their strength and performance. Resistance training stands out as the most effective method for building muscle strength and promoting hypertrophy. Established research emphasizes key principles, such as training close to failure to optimize muscle growth.

However, a critical question arises: should one focus on a particular contraction type when lifting weights?

A concentric contraction occurs when a muscle shortens, such as when performing a bicep curl. During this phase, the biceps become more prominent as they contract, drawing the forearm closer to the shoulder. In contrast, the eccentric contraction refers to the lengthening of the muscle, exemplified by lowering the weight in a bicep curl.

Recent research has investigated the effects of concentric-only, eccentric-only, and a combination of both contraction types on bicep strength and growth. Participants were divided into four groups: concentric only (14), eccentric only (14), a mix of concentric and eccentric (14), and a control group (11) that did not engage in exercise.

Each training group completed 3 sets of 10 bicep curls at a consistent intensity, conducted twice a week. The primary distinction among the groups was the type of contraction performed.

The overall training load varied, with the combination group lifting in both directions. The total volume for the combination group reached 5745 kg, whereas the concentric and eccentric groups saw totals of 2930 kg and 3035 kg, respectively.

At the conclusion of the five-week study, results indicated that the eccentric phase was particularly beneficial. Both the combination and eccentric groups exhibited significant gains in eccentric torque, increasing by 12.5% and 16.2%, respectively. All groups saw improvements in concentric torque, but the combination group experienced the most considerable increase at 17.5%, followed by the eccentric and concentric groups at 14.2% and 10.5%, respectively. Although the differences were not statistically significant, they were noteworthy compared to the control group.

Muscle thickness showed marked improvements in the combination (10.6%) and eccentric (9.7%) groups, while the concentric group only recorded a 2.5% increase.

The researchers concluded that "Eccentric training increased muscle strength and thickness comparably to concentric-eccentric training, despite requiring only half the training volume, indicating minimal contribution from concentric contractions."

Chapter 2: The Superiority of Eccentric Training

One of the primary advantages of eccentric training lies in its ability to generate greater mechanical tension than concentric training. For instance, if your maximum bench press is 200 pounds, your limitation arises during the concentric phase when lifting the weight off your chest, not during the eccentric phase when lowering it.

Interestingly, during eccentric contractions, more force is produced, despite the resistance remaining constant and overall training volume being lower. This phenomenon occurs due to both passive and active processes within the muscle. Active actions lead to increased cross-bridge formation between muscle proteins (actin and myosin), while passive actions stem from the spring-like properties of proteins like titin.

The enhanced force generation and the stretch response during eccentric lifts may stimulate higher levels of muscle protein synthesis, fostering greater muscle mass.

Does this imply that concentric contractions should be eliminated from workouts?

Chapter 3: The Importance of Concentric Movements

It’s essential to address limitations from the bicep curl study. The participants were untrained, meaning they could achieve muscle growth and strength more rapidly with lower exercise volume than trained individuals. For someone who regularly exercises, the additional load from concentric movements may be necessary for noticeable adaptations.

Moreover, research indicates that the concentric phase can provide complementary benefits, yielding distinct morphological and neurological adaptations. Strength is specific to the task; for example, while increasing bicep size will assist with pull-ups, the most effective way to improve pull-up performance is through practicing pull-ups. This principle applies universally to exercises; for instance, leg presses bolster leg strength, but squats yield greater improvements for squatting.

It's also crucial to consider delayed onset muscle soreness (DOMS). Eccentric movements typically cause more muscle damage and DOMS than concentric actions. The overall volume in the bicep study was lower for the eccentric group, meaning if the volume had been equalized by doubling eccentric repetitions, participants might not have adequately recovered.

Training exclusively with eccentrics can lead to overtraining, especially if one consistently lifts beyond their concentric capacity.

Practical Insights for Training

• Do not neglect the eccentric phase of lifts.
• While focusing solely on eccentrics is not advisable, integrating them can lead to substantial strength and muscle mass gains.
• Relying only on eccentric training might not save gym time; instead, it could extend workout duration since concentric actions provide a quicker return of the weight to the starting position.
• Other techniques (like super sets, drop sets, and rest-pause) may be more effective for reducing gym time while maximizing results.

To achieve optimal results in muscle growth, strength enhancement, or sport-specific movements, incorporating the eccentric phase in your training regimen is essential.

For more health and fitness insights, check out the Clinical Gap Podcast, with new episodes released weekly. For concise summaries of health and fitness research, subscribe here.