Original Mountain Marathon (OMM)

Looking to strike the right balance between warmth and weight is difficult when conditions on the OMM can vary between wet and wild at one extreme and decidedly chilly, even freezing, at the other. On cold mountain nights one wants to rest and sleep well.

OMM Sleeping Bags

The three PHD sleeping bags most suitable for the OMM are the M.Degree 200 K, the M.Degree 250 K and the M.Degree 300 K. All three bags are very lightweight. The M.Degree 200 K excels at saving weight and space in your pack, while the M.Degree 300 K provides extra warmth if the temperature dips. For many the M.Degree 250 K hits the weight to warmth ratio sweet spot.

The M Degree 200 K has been used below zero on many occasions, but mostly in competitions where only one or two nights camping were involved. The OMM can be a fully committing mountain race though, and under cold conditions the argument for extra insulation is strong.

For even more weight saving, consider a hoodless sleeping bag. The Delta Race 200 K is one of the most extreme lightweight bags ever made and combines with the buff or woolly hat you already have.

The basic figures for the above bags:

S-bag TOT (Min Temp) Weight Packed size
Hght x Diam (cm)
F gm oz 
M.Degree 200 K 4 39 340 12 21 x 13
M.Degree 250 K 0 32 390 14 21 x 13
M.Degree 300 K -3 26 445 16 21 x 13
Delta Race 200 K 4 36 300 11 21 x 13

For mountain races, particularly where only one or two nights’ camping are involved, there is a strong incentive to travel as light as possible. Combining the M.Degree 100 K or Delta Race 100 K sleeping bag with down clothing—such as our Wafer Ultima K Jacket—is another potential option to secure a good night’s sleep. A full set of our Wafer down clothing (top, trousers and socks) will provide a 5°C lift to the temperature rating of your sleeping bag.

Additional points:

  1. TEMPERATURE RATING: Put simply, these are the temperatures at which you should be able to get a night's sleep in normal circumstances. For fuller details about the TOT rating see this Technical Briefing.
  2. LINERS: A liner will add to the insulation if you choose the M.Degree° 200K but want more warmth. As always it is a trade-off between the extra weight & bulk and the warmth you gain (maybe 2°C). Silk liners at 140g are a popular choice but, for a greater boost of extra warmth, our K-Series Filler Bag will add 10°C to the bag’s TOT for a weight of just 240g.
  3. CLOTHING: Thermals (if you are taking them) and/or other clothing obviously help to keep you warm. The Wafer/Wafer Ultima clothing adds considerable warmth for minimal weight. Even warmer but still very light is the K-Series Ultra Down Vest at 150gm. See the Clothing section below for more details.
  4. FABRIC OPTIONS: The M.Degree and Delta Race bags come with very lightweight fabric as standard, but are also available in Hypershell. This is highly wind/water resistant, which is particularly useful for shedding condensation in small tents, and only adds about 15gm to the total weight. 
  5. The M.Degree and Delta Race bags are also available with a waterproof footbag (racing tents can be pretty cramped and it’s easy to end up sleeping with feet pressed against wet fabric) which can be permanently fixed in place, or detachable to allow stripping down for ultralight overnights.
  6. ZIPS: None of these bags has a zip. Zips are an option, but most competitors don't ask for one. A short zip with draft tube adds about 50gm (2oz): a full zip and tube adds about 110gm (4oz). Zips also add to the packed size. A further option is the footzip, which only adds about 10g (⅓ oz). Designed for venting tired feet on desert ultras, it’s perhaps less relevant for the OMM, but you may of course have plans for hotter races.
  7. PACKED SIZE: PHD stuff sacs tend to be on the relaxed side. All these bags can be compressed further in your sack.

OMM Down Clothing selection

The OMM weekend commits the racer to a quite considerable time at the evening campsite after the first day's racing. What's more, the clocks move back an hour at 2:00 a.m. on the Sunday morning, meaning an even longer period in camp before the chance to warm up on the second day of racing.

The use of down clothing to create a layered Sleep System while in your sleeping bag – and for wearing around camp of course – is worth considering for ultimate weight saving and provision of warmth. Our Wafer/Wafer Ultima range of clothing was designed with this in mind: a fraction of the weight of fleece (and an even smaller fraction of the bulk), but totally windproof and capable of keeping you warm down to round about freezing point.

To boost your sleep-system, a full set of Wafer clothing (jacket, trousers and socks) will add 5°C to the temperature rating of your sleeping bag and, when you wriggle out of your sleeping bag in the morning (or the night), you will experience far less of a temperature drop to shock your system!

The next Original Mountain Marathon takes place in the Southern Highlands, starting on 26th October 2024.


Photo: Eric Rayner