Ride steep climbs: seated position, weight on the nose of the saddle, smooth pedalling and when standing makes sense. With milestones and common mistakes.
The honest answer: on steep climbs you normally ride seated, with your upper body forward and your weight on the nose of the saddle, so the front wheel does not lift and the rear wheel does not spin. There is no study that measures exactly this mountain bike position. What exists are association curricula and lab studies from road cycling, which this guide relies on.
How hard is it really? On short ramps you get it after a few rides. On loose ground, with roots and steps, it becomes a concentration task. That is why the DIMB includes climbing in its basic safety module, next to ready position and braking [1].
Uphill you do not lose power, you lose grip.
Shift down before the slope begins. Shifting under load means power loss and a grinding chain. You want to pedal steadily without the pedals getting heavy.
Milestone: you reach the slope in the right gear and do not have to shift again until the middle.
Slide onto the front half of the saddle, upper body forward, elbows bent, head over the handlebar. That puts weight on the front wheel so it does not lift. At the same time enough weight stays at the rear for traction (practice).
Milestone: in the side video neither wheel rears up, and the rear wheel does not spin on firm ground.
Constant pressure, no jerks. On loose ground the rear wheel cannot take power spikes. Count in your head: even down, even through.
Milestone: 30 seconds steeply uphill without a wheel spinning or lifting.
Look 5 to 10 metres ahead and find the grippiest strip. Do not ride over roots and loose leaves if you can move sideways.
Milestone: you spot the best line before the climb and do not change it mid-slope.
Standing is a tool for spikes, not a permanent state. When you stand up, your centre of mass shifts forward and the bike sways, which in a study of 13 elite cyclists on a treadmill raised the mechanical cost by 4.3 percent [2]. That was road cycling, but the principle holds: standing costs.
Milestone: you stand briefly for a step, sit straight back down and keep grip.
Uphill you fall slowly, but onto hard ground. Wear a helmet and gloves; in a meta-analysis of cyclists a helmet cut serious head injuries by about 60 percent [5]. That is cycling in general, not mountain biking specifically, but a useful guide value.
Do not charge steep sections you do not know. Dismount when you feel the rear wheel or your strength failing: dismounting is technique, not failure. The DIMB explicitly treats dismounting on slopes as a learning topic [1]. This guide explains and motivates; it does not replace supervised training.
Switch deliberately between sitting and brief standing. In a study of ten elite cyclists who changed every 10 seconds between sitting and standing on a 6.8-degree treadmill incline, blood lactate was lower than with continuous sitting or standing [6]. That was at easy intensity and on a treadmill, not a mountain bike. Try it on long climbs: two minutes seated, 15 seconds standing, back to sitting (my suggestion, not a study value). What matters is that the change is part of your rhythm.
At moderate power you can generally sit: in one study time to exhaustion at 86 percent of maximum power was the same seated and standing, and only above about 94 percent did standing pay off [4]. On loose ground you also stay seated so the rear wheel keeps grip.
Your centre of mass is too far back or you pedal too jerkily. Slide onto the nose of the saddle, bring your upper body forward and pedal evenly. The front wheel stays down when there is pressure on it (practice).
Small gear before the climb, upper body forward, pick a line with grip and pedal evenly. If you feel it will not work, dismount. That is better than a crash.
Less pressure gives grip on loose ground, but too little raises the risk of a pinch flat. There is no general number. Try small steps and watch the surface (practice).
Cornering on a Mountain Bike: Lean the Bike, Weight the Outside Foot, Look Through the Turn