In this post, we discuss eccentric control, and what the lowering phase of a repetition can reveal about your muscles.
The half of the rep almost nobody does well
Watch anyone train for five minutes and you’ll see the same pattern. The weight goes up with effort and intent. Then it comes down with little, if any, control.
That lowering phase is called the eccentric portion of a repetition: the muscle is working while it lengthens. Most people treat it as a recovery between reps. It can, however, be the most informative part of the movement.
In my experience, two things reliably point to a muscle that’s been overloaded in the past. It can’t fully shorten, and it has trouble lowering a weight with control. Slow the lowering phase down and this becomes more evident.
Strongest on paper, hardest to control
Here’s the paradox. Mechanically, lowering is the strongest thing a muscle can do. This is because the cross-bridges within the structure of a muscle resist being pulled apart, and a spring-like protein called titin stiffens as the muscle lengthens.
Because so much of the force comes free from passive mechanics, the nervous system’s job changes. On the way up it drives the muscle. On the way down it has to throttle it, with fewer motor units firing at lower rates. Braking smoothly is a harder control problem than pushing hard.
The spinal cord steps back, the brain steps in
Muscle control runs on two levels. The spinal cord handles fast reflexes, driven by muscle spindles that sense stretch. The brain handles planning, grading and judgement.
During lengthening, the spinal level is deliberately turned down. Reflex responses measured during eccentric work are consistently smaller than during lifting or holding, and this is mainly attributed to inhibition in the spinal cord.
In the brain, however, EEG recordings show the opposite: greater cortical activity, and longer preparation, for lowering than for lifting, even though the muscle itself is less active.
So it’s reasonable to infer that lowering relies more on the brain.. That matters, because the brain is exactly where injury, pain, fear and ageing leave their mark.
A brake that can change with training
Even in healthy people, the nervous system holds back during eccentric contractions. In knee-extensor studies by Westing, Seger and Thorstensson, for example, maximal voluntary eccentric torque was similar to isometric and didn’t rise with speed. Superimposing electrical stimulation on that maximal effort increased torque specifically during lowering. This suggests the capacity is there, but the brain and spinal cord simply won’t use it.
This brake is adjustable however. Heavy resistance training partly removes the suppression of muscle activation during maximal lowering, alongside gains in eccentric strength. The nervous system loosens its grip as tissue demonstrates it can cope.
What a slow descent reveals
A slow eccentric won’t tell you whether a problem sits in the spinal cord or the brain. What it does reveal, however, is a muscle the nervous system no longer trusts. In practice, this looks like:
- Fast drops: the weight drops faster at a particular point in the range.
- Shaking: tremor appears during lowering that isn’t there during lifting.
- Giving way: control holds, then suddenly lets go near the long end of the range.
- Bracing: the person stiffens the whole limb rather than using the isolated muscle.
- Side-to-side differences: one limb lowers smoothly, the other doesn’t.
Older adults should focus on eccentric contractions
I see this most dramatically in older untrained clients, and the research helps explain why. Their maximal eccentric strength holds up relatively well with age; it’s the force control that deteriorates.
Older adults are less steady when lowering than when lifting, which isn’t true of young adults. In the quadriceps, the gap in force steadiness between older and young adults is biggest during lowering. Several things combine to produce this
- Coarser motor units: with age, motor neurons are lost and surviving ones take over orphaned fibres, so units become fewer and larger and force comes in bigger, rougher steps.
- Noisier firing: older motor units discharge more variably. Eccentric work already runs at the low firing rates where that matters most.
- Poorer feedback: muscle sense is thought to decline with age, thinning an already dampened signal.
This matters because so many everyday movements are lowering tasks. Sitting down, going down stairs and stepping off a kerb all depend on controlling a muscle as it lengthens, and they’re exactly the situations in which older people fall.
As control fades, many people start avoiding lowering altogether. They drop into chairs rather than sitting down, and lean on the banister to take the load off their legs on the stairs. That feels safer in the moment, but it removes the very practice that keeps the skill alive, so control declines further and the next fall becomes more likely.
How to improve your control of eccentric contractions
The fix follows from the problem. If the nervous system has tightened its brake because it doesn’t trust the tissue, you earn that trust back with exposure the system can tolerate.
- Take 4 to 5 seconds to lower a weight. It gives the brain time to grade output, and it shows you exactly where control breaks down.
- Build range gradually. Work where control is clean, then extend towards the range that wobbles.
- Use long-length holds as a bridge. Holding a weight still at a longer muscle length is often tolerated before full lowering is.
- Train eccentrics deliberately. Strength training improves the steadiness of slow lowering in older adults.
Summary
Lowering is the strongest thing a muscle can do but the hardest to control, because the nervous system has to brake rather than drive it, and leans more on the brain to do so.
That control is often the first thing to change after injury and with age, which matters because sitting, stairs and kerbs are all lowering tasks. Slowing the lowering phase down both reveals where control breaks and is how you rebuild it.
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