Constant Resistance Exercise: Definition, Examples, and Benefits

What is an example of a constant resistance exercise?

A classic example of a constant resistance exercise is the barbell bicep curl, where the weight of the barbell provides a consistent load throughout the range of motion, primarily due to the unchanging force of gravity acting on the mass.

What is Constant Resistance?

In the realm of strength training, resistance refers to the external force that a muscle must overcome to produce movement. Constant resistance is a form of training where the external load applied to the muscles remains uniform throughout the entire range of motion of an exercise. This stands in contrast to variable resistance, where the load may change at different points in the movement (e.g., through the use of resistance bands, chains, or specialized cam-based machines that alter the leverage).

The most common and fundamental source of constant resistance is gravity acting on a fixed mass. This is why exercises performed with free weights—such as barbells, dumbbells, and kettlebells—are prime examples of constant resistance training. The mass of the weight does not change, and the gravitational pull on that mass is constant, thereby providing a consistent downward force.

The Mechanics of Constant Resistance

While the external load (the weight) in constant resistance training remains the same, it's crucial for fitness professionals and enthusiasts to understand that the internal muscular force required to move that load can vary throughout the exercise. This is due to changes in leverage and the "strength curve" of the muscle. For instance, during a bicep curl, the muscle is strongest in the middle of the range of motion and weaker at the very beginning and end. Even though the barbell's weight is constant, the mechanical advantage (or disadvantage) changes, making certain parts of the lift feel harder than others. This inherent characteristic is a key aspect of free-weight training.

Example: The Barbell Bicep Curl

The barbell bicep curl is an excellent illustration of a constant resistance exercise.

• Muscles Engaged: The primary movers are the biceps brachii, along with the brachialis (lying underneath the biceps) and the brachioradialis (a forearm muscle that assists in elbow flexion).
• Movement Phases:
  • Concentric Phase (Lifting): Starting with the barbell in hand, arms extended downwards, the elbows flex to bring the barbell upwards towards the shoulders. During this phase, the biceps contract and shorten.
  • Eccentric Phase (Lowering): From the top position, the barbell is slowly and controlled lowered back to the starting position. The biceps lengthen under tension, acting as brakes against the force of gravity.
• Why it's Constant Resistance: The weight of the barbell itself does not change at any point during the movement. Whether the barbell is at the bottom, middle, or top of the curl, its mass remains the same, and the gravitational pull on it is constant. Therefore, the external resistance applied to the biceps is consistent throughout both the concentric and eccentric phases of the lift. While the moment arm (the perpendicular distance from the joint to the line of action of the force) changes, altering the torque on the joint, the load itself is constant.

Other Examples of Constant Resistance Exercises

Many foundational strength training exercises fall under the category of constant resistance, particularly those utilizing free weights:

• Barbell Squat: The resistance is the constant weight of the barbell and plates.
• Dumbbell Bench Press: The dumbbells provide a consistent downward force.
• Overhead Press (Barbell or Dumbbell): The weight of the implement remains unchanged throughout the press.
• Deadlift: The barbell's weight provides constant resistance from the floor to lockout.
• Barbell Row: The resistance of the barbell is constant as it's pulled towards the torso.
• Dumbbell Lunges: Each dumbbell maintains its constant weight as you lunge.
• Calf Raises (with dumbbells or barbell): The added weight provides constant resistance to the calf muscles.

Benefits of Constant Resistance Training

Constant resistance exercises, particularly with free weights, offer numerous advantages for fitness enthusiasts and athletes:

• Develops Functional Strength: They closely mimic real-world movements and require the body to stabilize the weight, building strength that translates well to daily activities and sports.
• Enhances Stability and Proprioception: The need to control and balance the free weight recruits stabilizing muscles and improves body awareness.
• Versatility and Accessibility: Free weights are widely available in gyms and can be used for a vast array of exercises.
• Promotes Progressive Overload: The ability to incrementally increase the weight allows for consistent challenge and adaptation, which is fundamental for muscle growth and strength gains.
• Cost-Effective: For home gyms, a set of dumbbells or a barbell with plates is a relatively affordable and highly effective investment.

Considerations and Limitations

While highly effective, constant resistance training does have certain considerations:

• Strength Curve Mismatch: As mentioned, the constant load may not perfectly align with the muscle's strength curve, meaning the muscle might not be maximally challenged at all points in the range of motion.
• Higher Skill Requirement: Free weight exercises often demand greater technical proficiency and core stability compared to machine-based exercises, increasing the risk of injury if form is poor.
• Limited Variability in Stimulus: Unlike variable resistance tools (e.g., resistance bands or chains), constant resistance doesn't inherently provide accommodating resistance that matches the changing strength curve.

Conclusion

The barbell bicep curl stands as a quintessential example of a constant resistance exercise, embodying the fundamental principles of strength training with free weights. Understanding constant resistance is crucial for designing effective training programs, as it forms the bedrock of many foundational movements. By consistently applying a fixed external load against the force of gravity, constant resistance exercises effectively build strength, muscle mass, and functional capacity, making them an indispensable component of any comprehensive fitness regimen. Always prioritize proper form and progressive overload to maximize benefits and minimize injury risk.