Debunking the 'Always Lift Slow' Myth
The Science of Rep Speed and Muscle Actions
Strength & Muscle Course: Tweet 5 - Slow Reps or Fast Reps?
Many fitness influencers misleadingly claim that you should always move slowly with weights. Here's why you should not listen to them.
There are two types of exercises: isotonic and isometric. There is a third kind called isokinetic, but I won't discuss it as it's not relevant to most of you. An isotonic exercise involves movement of the muscles with a constant load. For example, when you perform a bicep curl or a squat, your muscles shorten and lengthen as they contract and relax, which is characteristic of isotonic exercises.
On the other hand, an isometric exercise involves muscle contraction without movement. In this type of exercise, the muscle doesn't change length, and the joints don't move. An example of this is holding a plank position, where you engage your muscles but remain still.
An isotonic exercise consists of two types of muscle actions: concentric and eccentric. During a concentric action, the muscle shortens as it contracts (positive phase of an exercise). For instance, when lifting a dumbbell in a bicep curl, the biceps muscle shortens. In contrast, during an eccentric action (negative phase of an exercise), the muscle lengthens while still under tension. An example of this is the lowering phase of the bicep curl, where the biceps control the downward motion, slowly lengthening as they resist the weight.
Today, we'll learn how and why to integrate these three muscle actions: concentric, eccentric, and isometric. I have seen a few fitness influencers give the misinformed blanket advice that everyone should always move weights slowly during both the concentric and eccentric phases, which makes this post even more important.
Concentric Contractions
Definition: Muscle shortens while generating force, overcoming resistance. This action happens during the "lifting" phase of most strength training exercises.
Example: Lifting phase of a bicep curl, pushing up during a bench press, jumping up during a squat jump
Important Points:
Positive phase of an exercise.
Primarily responsible for movement and acceleration.
Generates less force compared to eccentric contractions at the same muscle length.
Important for building strength and power (and also hypertrophy).
Usually the focus in traditional strength training.
Requires more metabolic energy (ATP) per unit of force produced, making it more energy-intensive.
General Recommendation: Accelerate during this phase (aim to move as fast as possible).
Eccentric Contractions
Definition: Muscle lengthens while generating force, resisting the load. This happens when you lower a weight or decelerate during movement.
Example: Lowering phase of a bicep curl, lowering down during a push-up, descending into a squat or push-up, running downhill or landing from a jump
Important Points:
Negative phase of an exercise.
Essential for deceleration and controlling movement.
Generates more force than concentric contractions at the same muscle length. - Leads to greater muscle damage and potential for growth.
Can cause more muscle soreness due to higher muscle damage (leads to delayed onset muscle soreness, or DOMS).
Plays a crucial role in muscle hypertrophy and strength gains.
Consumes less ATP per unit of force.
General Recommendation: Decelerate during this phase (aim to move slowly and with control).
Isometric Contractions
Definition: Muscle contracts without changing length, holding a static position. There is no visible movement, but the muscle is actively working to hold a position.
Example: Holding a plank, wall sits, pausing at the bottom of a squat or push-up.
Important Points:
Generates more force than concentric actions but less than eccentric.
Can be used to improve strength at specific joint angles (angle-specific strength).
Useful for rehabilitation.
Can improve tendon strength.
Less effective for building muscle size compared to concentric and eccentric contractions.
Can be used to overcome sticking points in exercises.
Can improve stability and core strength.
Concentric contractions are vital for producing power and explosiveness in movements such as jumping, sprinting, and throwing. You can train to improve acceleration by focusing on the concentric phase of explosive movements. Most sport-specific movements, such as sprinting or pushing off the ground, are concentric. Training for fast, powerful concentric movements helps you perform better in these areas. Include exercises with a focus on explosive concentric phases, like power cleans, squats, and plyometrics to improve power output and speed.
Eccentric actions create more micro-tears in muscle fibers, leading to greater muscle growth when recovered properly. Eccentric training strengthens connective tissue and enhances control during deceleration, reducing the risk of injury in activities like running, jumping, and cutting. Eccentric-focused lifts allow you to use more weight than in concentric movements, building greater overall strength. In sports that involve deceleration or landing, such as basketball, soccer, or football, eccentric strength is essential for injury prevention and performance. Incorporate slow, controlled eccentric phases in exercises like squats or deadlifts. Consider eccentric overload training, where you lift more weight during the lowering phase, to maximize strength and hypertrophy.
Isometric contractions build strength in specific ranges of motion, which can improve stability and control in various athletic movements. Isometrics can be used to strengthen muscles without excessive joint movement, making them a valuable tool in rehabilitation. Holding isometric positions helps build muscular endurance, particularly in stabilizer muscles, which are essential for maintaining good posture and technique during dynamic movements. Isometric strength is essential in sports that require static holds or maintaining a specific position, such as wrestling, gymnastics, and rock climbing. It also helps you maintain body control in positions like squatting or lunging. Add isometric pauses in compound lifts (e.g., pausing at the bottom of a squat) to build strength at weak points in the range of motion. Also, use isometrics for core stability training, such as planks.
Program Design Tips:
Concentric: Focus on fast, explosive lifts like squats, cleans, or jumps for power.
Eccentric: Slow down the lowering phase of lifts or perform eccentric overload exercises to build strength and muscle size.
Isometric: Add static holds at challenging points during exercises or use dedicated isometric exercises like planks or wall sits for stability and endurance.
Why the Claim to Always Move Slowly is Misleading
Neglect of power and explosiveness
Inefficient strength development
Loss of training variety
We teach our bodies to accelerate during the concentric phase and decelerate during the eccentric phase.