Exercise: Reps, Time Under Tension, and Training Goals

Is it better to do more reps or more time under tension?

The choice between focusing on more repetitions (reps) or extended time under tension (TUT) is not mutually exclusive; rather, they are interconnected variables, and the optimal approach depends entirely on your specific training goals, whether it's strength, hypertrophy, or endurance.

Understanding Repetitions (Reps)

A repetition refers to a single complete execution of an exercise movement, from its starting position through its full range of motion and back to the start. Reps are the most fundamental unit of training volume.

• Primary Role: Repetition ranges are traditionally associated with different training adaptations:
  • Low Reps (1-5): Primarily for maximal strength and power development, using heavy loads.
  • Moderate Reps (6-12): Optimal for muscle hypertrophy (growth) and developing a balance of strength and endurance.
  • High Reps (15+): Focus on muscular endurance and local muscle fatigue, typically with lighter loads.
• Physiological Basis: The number of repetitions directly influences the total mechanical work performed and the amount of force produced over a set. Higher reps often lead to greater metabolic stress (accumulation of byproducts like lactate), while lower reps with heavier loads emphasize mechanical tension and neural adaptations.

Understanding Time Under Tension (TUT)

Time Under Tension (TUT) refers to the total duration a muscle is under strain during a set. It's the cumulative time your muscles are actively engaged and resisting a load, encompassing the concentric (lifting), eccentric (lowering), and isometric (holding) phases of an exercise.

• How to Measure/Manipulate TUT: TUT is typically manipulated by controlling the tempo of an exercise. A common notation is a four-digit code (e.g., 2-0-1-0):
  • First Digit: Eccentric (lowering) phase duration in seconds.
  • Second Digit: Isometric hold at the stretched position (bottom of a squat) duration.
  • Third Digit: Concentric (lifting) phase duration.
  • Fourth Digit: Isometric hold at the contracted position (top of a bicep curl) duration.
  • For example, a 3-1-2-0 tempo for a bicep curl means 3 seconds to lower, 1-second pause at the bottom, 2 seconds to lift, and no pause at the top.
• Primary Role: Manipulating TUT is often emphasized for:
  • Muscle Hypertrophy: Extended TUT, particularly with controlled eccentric phases, can increase muscle damage (a stimulus for growth), metabolic stress, and activate a broader range of muscle fibers.
  • Improved Mind-Muscle Connection: Slower, controlled movements enhance proprioception and the ability to "feel" the target muscle working.
  • Joint Health: Controlled movements reduce momentum and can be safer for joints.
• Physiological Basis: Extended TUT can increase the duration of mechanical tension on muscle fibers, leading to greater muscle fiber recruitment, especially slow-twitch fibers that are more endurance-oriented, and enhance the anabolic signaling pathways for muscle growth.

The Interplay: Reps and TUT

It's crucial to understand that repetitions and time under tension are not independent variables; they are inherently linked. Every repetition has an associated time duration, and thus contributes to the total TUT of a set.

• TUT is a function of Reps x Tempo: If you perform 10 reps with a fast tempo (e.g., 1-0-1-0, 2 seconds per rep), your TUT would be approximately 20 seconds. If you perform the same 10 reps with a slower tempo (e.g., 3-0-2-0, 5 seconds per rep), your TUT would be 50 seconds.
• Manipulating one impacts the other: By slowing down your tempo to increase TUT, you will naturally find that you can perform fewer repetitions with the same load, or you'll need to use a lighter load to complete the same number of reps.

Which is "Better"? It Depends on Your Goal

There isn't a single "better" approach; the optimal strategy integrates both concepts based on your training objective.

• For Maximal Strength:
  • Focus: Lower reps (1-5), very heavy loads.
  • TUT Implication: While the overall set TUT might be low due to fewer reps, the intensity of tension per rep is extremely high, maximizing mechanical tension and neural drive. Concentric phases are often explosive, leading to minimal TUT in that phase.
• For Muscle Hypertrophy (Growth):
  • Focus: Moderate reps (6-12), moderate to heavy loads.
  • TUT Implication: This rep range, combined with a controlled tempo (e.g., 2-0-2-0 or 3-1-1-0), often yields a TUT per set of 30-60 seconds, which is widely considered optimal for muscle growth due to a balance of mechanical tension, muscle damage, and metabolic stress.
• For Muscular Endurance:
  • Focus: Higher reps (15+), lighter loads.
  • TUT Implication: This naturally leads to higher total TUT per set (e.g., 60+ seconds), emphasizing the oxidative capacity of the muscle and resistance to fatigue.
• For Power:
  • Focus: Lower reps (1-5), moderate to heavy loads, explosive concentric phase.
  • TUT Implication: Minimal TUT during the concentric phase, as the goal is to move the weight as quickly as possible. The emphasis is on force production rate, not prolonged tension.

Practical Application: How to Manipulate Reps and TUT

To effectively integrate reps and TUT into your training:

• Vary Your Tempo: Don't always lift and lower at the same speed. Experiment with:
  • Slower Eccentrics (Negative Training): Emphasize the lowering phase (e.g., 3-4 seconds) to increase muscle damage and hypertrophy stimulus.
  • Isometric Holds: Incorporate pauses at specific points in the range of motion (e.g., holding at the bottom of a squat or the top of a pull-up) to increase localized tension and recruitment.
• Periodize Your Training: Cycle through different rep ranges and TUT strategies over time to provide varied stimuli and prevent plateaus. For example, a strength block might focus on low reps and heavy loads, followed by a hypertrophy block emphasizing moderate reps and controlled TUT.
• Prioritize Form: Regardless of your chosen tempo or rep scheme, maintaining proper form is paramount to prevent injury and ensure the target muscles are effectively worked. Sloppy reps with extended TUT are counterproductive.
• Consider Exercise Type: Some exercises lend themselves better to TUT manipulation (e.g., bicep curls, leg presses) than others (e.g., Olympic lifts, plyometrics).

Key Considerations and Potential Pitfalls

• Form Degradation: Excessive focus on slow tempos can sometimes lead to a loss of proper form if the load is too heavy or fatigue sets in too early.
• Reduced Load: To achieve longer TUT, you often need to reduce the weight, which might compromise the mechanical tension necessary for strength gains.
• Over-Fatigue: Constantly training with very high TUT can be mentally and physically demanding, potentially leading to overtraining if not managed properly.
• Progressive Overload Remains Key: Whether you manipulate reps, load, or TUT, the principle of progressive overload (gradually increasing the demand on the muscles) is fundamental for continued adaptation and progress.

Conclusion: A Synergistic Approach

Ultimately, the question isn't whether to do "more reps" or "more time under tension," but rather how to intelligently combine and manipulate both variables to achieve your fitness goals. Reps provide the framework for volume, while tempo (and thus TUT) dictates the quality and type of tension applied during those reps.

For a well-rounded and effective training program, you should employ a variety of rep ranges and tempo strategies. By understanding the unique contributions of both repetitions and time under tension, you can design a more precise and effective training regimen that continually challenges your body and drives the adaptations you seek.