Mountain Biking

Move · High-Intensity · Movement, Typed Supps

The forearms are often working hardest on the descents, when the legs have stopped pedalling altogether.

Stage by stage

Across the ride (Mixed energy systems): Sustained aerobic climbing alternates with supra-threshold surges over features, and neither quality substitutes for the other.
Out of the saddle (Eccentric absorption): The legs stop producing propulsion and start absorbing terrain input, working continuously while the drivetrain does nothing.
On the descent (Isometric grip under vibration): Braking holds the finger flexors contracted while vibration raises the force needed to keep hold of the levers.
When it goes wrong (Upper-limb crash pattern): Falls at speed onto hands and shoulders make clavicle fractures and wrist injuries the characteristic acute problems.

Muscles trained

Primary: quads, glutes, forearms
Secondary: calves, abs, heart, lungs

Intensity

8.5 METs (Bicycling, mountain, general).

Time to effect

Weeks: Line reading over rough terrain, braking control, and the grip endurance to hold on through rough descents improve within the first few weeks of regular riding.
Months: The aerobic base to sustain climbing efforts over a full ride, along with the instinctive body positioning that lets technical descents feel controlled rather than chaotic, build up over months of consistent time on the trail.

Related supplements

Common myth

Mountain biking is easier on the body than road cycling because suspension absorbs the impact. In reality: Suspension reduces peak shock but does not eliminate the muscular demand of constantly repositioning body weight over unpredictable terrain, and the sustained forearm grip strength and full-body stabilization required often make technical trail riding more physically taxing than steady-state road riding.