32-Second Time Under Tension

The concept of intentionally controlling repetition speed, or tempo, was popularized by strength coaches Ian King and Charles Poliquin. They developed notation systems, typically using 3 or 4 numbers, to prescribe specific durations in seconds for the lowering (eccentric), paused (isometric), and lifting (concentric) phases of an exercise. A typical tempo prescription might read "4010," directing a 4-second lowering phase, no pause at the bottom, a 1-second lifting phase, and no pause at the top. Manipulating these numbers changes the "time under tension" (TUT) for a set, a key factor in stimulating muscle growth. Research suggests the optimal total time under tension per set for hypertrophy (muscle growth) is between 20 and 70 seconds. The 32-second set duration highlighted in the card falls squarely within this muscle-building window. While prolonged tension is important, studies indicate that individual reps lasting longer than 8-10 seconds may be less effective for growth. The sweet spot for a single repetition duration is generally between 2 and 8 seconds, emphasizing a controlled eccentric phase and an explosive, but intentional, concentric phase. Slower, controlled repetitions force the muscle to do the work rather than momentum, which can enhance the mind-muscle connection and recruit more muscle fibers. This method is often used to break through training plateaus by introducing a new stimulus without necessarily increasing the weight on the bar. Focusing on a deliberate tempo, particularly a slower eccentric (lowering) phase, is known to create more mechanical tension and metabolic stress, both of which are significant drivers of muscle growth. It also helps to improve technique and can reduce the risk of injury by reinforcing proper movement patterns.