Eccentric Phase
Also known as: Negative, Lowering phase, Lengthening contraction
The part of a rep where the working muscle lengthens under load — the lowering phase of a squat, the bar coming down in a bench press, the descent of a pull-up. Eccentric contractions produce more force than concentric ones and are the primary driver of both strength gains and muscle damage.
Formula
Per rep: eccentric tempo (seconds) — concentric tempo (seconds). A 3-1-2-1 tempo means 3s lowering, 1s pause at bottom, 2s lifting, 1s pause at top. Eccentric overload protocols use 105-130% of concentric 1RM for the lowering phase only.Example
Back squat at 100 kg. Concentric (standing up) = 2 seconds. Eccentric (controlled descent) = 3 seconds. Total time under tension per rep = 5s. Across a 5-rep set: 15s of eccentric load on the quads — typically where most of the hypertrophic stimulus lives.
How Afitpilot Uses This
Afitpilot doesn't currently capture per-rep tempo, but eccentric work is implicit in how exercise prescriptions are designed. Tempo-prescribed exercises (e.g. "3-0-1-0 tempo squat") flow through to the session card with the tempo notation preserved. The plan generator will favour controlled eccentric tempos for hypertrophy blocks and competition-style fast eccentrics for strength peaking blocks. Future surface: explicit tempo capture so per-rep time under tension can feed volume calculations alongside reps and tonnage.
Eccentric force vs concentric — what you can do
| Who / Context | Value | Note |
|---|---|---|
| Strength advantage | Eccentric ~120-140% of concentric | You can lower more weight than you can lift |
| Hypertrophy stimulus | Slow eccentrics (3-5s) at moderate load | Best stimulus-to-fatigue ratio for muscle growth |
| Tendon adaptation | Heavy slow eccentrics, 3x/week | Standard rehab protocol for patellar/Achilles tendinopathy (Alfredson) |
| Strength carryover | Fast eccentrics for sport | Stretch-shortening cycle relies on a brief, powerful eccentric |
| DOMS source | Eccentric > concentric, by ~5x | Unfamiliar eccentric volume is the main cause of severe soreness |
| Active aging (60+) | Eccentric training preserves type-II fibres | Better retention of fast-twitch muscle than concentric-only training |
Known Limitations
- •Eccentric overload (loads >100% of concentric 1RM) requires spotters or specialized equipment and is poorly suited to self-coached training — we don't prescribe it.
- •Tempo prescriptions only work if the athlete actually counts the seconds. Without video review or a metronome, prescribed tempos drift toward the athlete's natural rhythm within 2-3 sets.
- •Heavy eccentric work produces disproportionate muscle damage — DOMS from a single eccentric-emphasized session can last 5-7 days, longer than the supercompensation window would predict for the same total volume of mixed work.
Science Context
Eccentric contractions produce more force than concentric ones at any given velocity (Hill's force-velocity curve, 1938) and are mechanically distinct: the cross-bridge cycle works in reverse, and titin acts as a passive load-bearing spring. Research consistently shows eccentric-emphasized protocols produce equal or greater hypertrophy than concentric-only at matched volume (Schoenfeld et al., 2017 meta-analysis), and superior tendon remodelling. The trade-off is recovery cost: eccentric work generates significantly more EMG-detectable muscle damage and longer-lasting DOMS, which is why high-eccentric protocols are typically used in short blocks rather than year-round.