INFERNO Triathlon: Course, Elevation & Route Profile

Course & Elevation

The swim covers 3,000 metres from the Strandbad in Thun. The road-bike leg starts in Oberhofen and climbs straight away: 7.9 kilometres at a good 7 percent via Sigriswil to Beatenberg, then a descent to Interlaken and around forty flat kilometres up the valley to Meiringen. From kilometre 66 the Grosse Scheidegg follows, two linked climbs of 8.9 and 7.5 kilometres that top out just under 1,950 metres before the road drops to Grindelwald at a good 950 metres.

In Grindelwald you change onto the mountain bike, and the course removes every recovery phase: 10.8 kilometres averaging 10.2 percent up to the Kleine Scheidegg at just over 2,000 metres, then a long technical descent via Wengen to Lauterbrunnen and on to Stechelberg. Close to a third of this leg is steeply uphill and a good quarter steeply downhill. Handling counts for as much as strength here.

The run begins flat on the valley floor but turns after five kilometres: first 7.6 kilometres at 10 percent up to Mürren, then from kilometre 15.5 the closing climb at 15 percent average with ramps beyond 30 percent, 1,294 metres of ascent to Piz Gloria. More than half the run course is steep climbing terrain, and very little of it is actually run.

Pacing Strategy

The INFERNO needs a plan across four sections rather than three, and the order is unusual: the first climb arrives in the opening kilometres of the bike, straight out of the swim. Forcing it is the most common mistake, because forty flat kilometres follow in which the damage stays hidden for a long time.

The decisive point is the change from the road bike to the mountain bike. The Grosse Scheidegg ends in a fast descent to Grindelwald, and immediately afterwards a climb of more than a thousand metres begins in one piece. Ride the Scheidegg too hard and you lose more on the Kleine Scheidegg than you gained. Plan the bike change as a calm, complete reset, fuelling included.

The final climb to the Schilthorn is not a running course but a hiking course with a clock in your head. At 15 percent average, an even, economical hiking rhythm beats alternating between running and standing still, and the last kilometres sit above 2,500 metres, where any excess in heart rate is paid for immediately.

Training plan for INFERNO Triathlon: 12-week build

Age-group athletes typically need between 9 and 13 hours. The demand has little in common with a classic long-distance race: 5,500 metres of climbing spread over 155 kilometres, and apart from the valley section between Interlaken and Meiringen there is barely a stretch where an even aerobic output would be possible at all.

Three climbs decide the race: the Grosse Scheidegg on the road bike, the Kleine Scheidegg on the mountain bike and the Schilthorn ascent on foot. They sit so close together that almost no recovery happens between the first and the last; from Meiringen to the finish the course climbs with only two descents in between.

The main training emphasis is therefore climbing on both bikes. Train only on the road bike and you will underestimate the Kleine Scheidegg; train only on the mountain bike and you will lose the valley section. Combined sessions in which you genuinely swap bikes mid-ride, shoes and helmet included, are worth the logistics so the sequence is automatic on race day.

For the run, steep hiking is the most specific preparation: long ascents of 1,000 metres or more, deliberately done after several hours on the bike. Add the technical descent from Wengen to Lauterbrunnen, which asks for handling skill in a fatigued state, because you ride it hours into the race rather than fresh. And since the finish sits at close to 3,000 metres, at least one session at altitude belongs in the plan so you know how your body works up there.