Ben More and the Crianlarich hills: inspiration for Naismiths Rule

Ben More and the Crianlarich hills: inspiration for Naismith's Rule

Life, inevitably, has its ups and downs. And we hillwalkers love them.

It’s why we set out, week after week, to slog up another fell or mountain, panting both in anticipation of an increasingly panoramic view and at the pain of hauling our bodies and kit up the gradient. And after a sojourn spent putting names to peaks, chomping on sandwiches or even just trying to find the elusive summit cairn, it’s back down to the valley, lungs replenished, legs rejuvenated, at a rate much faster than the clomp up.

Or is it? Here’s a curious thing: that journey down the hill may not be quite as fast as you imagined.

I’ll let you into a secret here. For the past several months, we at grough have been working on a major mapping and route system that will be unveiled in a few weeks. As part of the service, grough route will enable users to plan the duration their walk, depending on how steep the path is, how long, and what type of terrain will be encountered.

The online system will have lots of features, many not available on any other route systems, but fundamental to the ability to plan and walk a route is the ability to forecast how long the journey, or legs of the trip, will take.

It’s not a new concept. In 1892, William Wilson Naismith devised the rule which, for more than 100 years, has been accepted as the best way to deal with the fact that human beings can’t walk uphill as fast as they can descend slopes. Naismith was an accomplished mountaineer, one of the founders of the Scottish Mountaineering Club.

Naismith’s Rule was the result of Willie’s May walking trip among the Crianlarich hills, taking in Cruach Ardrain, Ben More and Stob Binnein. Taking calculations as he tackled the three munros, he formulated the basic speed on good terrain of 3mph on the flat, with the addition of half an hour for every 1,000ft of ascent. Metricised, this has become 5km per hour with 30 minutes for every 300m climbed, which is handy because it can be easily measured as one minute per 10m contour line crossed.

So far, so good, though Naismith made no additional calculation for descent. Over the decades, many variations, corrections and adjustments have been put forward to enable the venerable chartered accountant’s rule to be made more accurate.

grough route will enable users to plot their speed and use OS mapping

grough route will enable users to plot their speed and use OS mapping

The most tortuous and probably the least commonly used are Tranter’s Corrections. For these, we have to be grateful to another Scottish mountaineer, Phillip Tranter. His table relies on working out your individual fitness and applying this to Naismith’s Rule to find out how long an ascent should take you. Tranter was himself quite a fit chap – he has a Glen Nevis circuit named after him and was the first man to do two rounds of the munros. According to Tranter, the time taken to rise 300m in a 800m linear walk puts you on the fitness scale between 50 – very unfit and 15 – which should see you chopping Naismith’s time in half.

Tranter’s Corrections also have further variations: walking with a headwind, a 20kg load and at night all mean coming down a fitness level, and terrain type can mean either one or two levels down on the scale. We could add that Smith’s variation on Tranter’s Corrections to Naismith’s Rule state that the number of units of alcohol consumed the previous evening is proportional to the level of nausea and cerebral pain experienced trying to achieve Tranter’s level 15.

Few but the most obsessively quantitative have more than a stab at an accurate rating on the Tranter scale. It helps, of course, if you have a handy 800m long 1,000ft hill outside your back door.

None of these really address any adjustment for coming downhill. Commonsense would suggest that it is going to be quicker descending than ascending. It’s important to be able to predict as accurately as possible when you are going to arrive at a certain point, particularly when conditions are less than ideal. Naismith is still at the heart of mountain training when candidates are taught to navigate for qualifications such as the mountain leader or walking group leader awards.

The ‘bible’ of mountain training was the late Eric Langmuir’s Mountaincraft and Leadership. Langmuir admits that descents provide a conundrum.

“Going downhill poses a bit of a problem,” he said. “Most walkers naturally increase their speed going down fairly gentle slopes of between about 5 degrees and 12 degrees. There comes a point, however, at which the time taken is more than would be taken walking the same distance on the level because of the extra care that is required.

“Over a day’s journey, it is normal practice to discount descent, on the assumption that increased speeds on the gentle descents will be compensated by slower speeds on the steep ones.”

He concludes that, for short distances, the following formula should be used: for gentle slopes downhill, reduce time by 10 minutes for every 300m of descent; for steeper slopes, add 10 minutes for every 300m you go down.

I’m not sure this calculation bears scrutiny. When we set about determining the default adjustments for the timing of legs on grough route, we encountered a problem here, of which more in a moment.

Hillwalking by Steve Long is ‘the official handbook of the Mountain Leader and Walking Group Leader schemes’. Long sticks with the generally held adjustment for downhill walking: “Although downhill sections can be ignored over greater distances, timing can be affected on individual sections,” Hillwalking says. “On gentle slopes, the effect of gravity allows slightly faster progress than on flat ground. As a rule-of-thumb, one minute for every 30m of descent can be subtracted from any timing calculations. Conversely, steep descents may require this amount to be added to the total time.”

Let’s take a close look at this: let’ say you descend a hill, walking for 1km down a slope at the steep end of the proposed adjustment, 12 degrees. Walking at 5km/hour, you would normally expect to cover the ground in 12 minutes.

However, a slope of 12 degrees over this distance will drop you 213m. Using the 10 mins per 300m descent formula, we should knock about seven minutes off our time, so the leg should take us about five minutes. In doing so, we would have covered the ground at 12km/hour.

Fellrunners are probably the only people who come down Pen-y-ghent at 12km/hour

Fellrunners are probably the only people who come down Pen-y-ghent at 12km/hour

Now, I don’t know about you, but I reckon 12km/hour is way beyond most walkers’ capabilities. In fact, the only people who regularly descend a hill at that rate are fellrunners and those unfortunate enough to have gone into a barrel-roll after stumbling on the way down.

grough’s programmer drew this anomaly to my attention, so I decided to conduct a very limited, and unscientific experiment: I walked up and down Pen-y-ghent, the diminutive but shapely fell overlooking Horton in Ribblesdale in the Yorkshire Dales.

I don’t pretend to be super fit, and could certainly do with losing a few pounds to help me get up the hill. I reckon my average walking speed is about 5.5km/hour, so it was interesting to analyse the results.

Up the long slog from Brackenbottom to the Pennine Way, my speed was round the 4km/hour mark, slowing to just 2k on the steep section on the hill’s southern escarpment. No great surprises there.

But coming downhill, whereas I might have expected to get up a good head of steam, I actually found I was as slow as some of the uphill legs, managing only 4km/hour at first. Only when the route really started to flatten out, with an angle of 5 or 6 degrees, did my pace approach 6km/hour.

So maybe it’s time to look again at the concept of taking away time for many hill descents. While admitting that the above experience was just one day’s short walk, the results were quite surprising to me.

grough route will enable you to put in your personal estimates for all kinds of terrain and slope: we want it to be as accurate and as useful to walkers and other outdoor users as possible, but we think we may have to rethink our default values. After many unquestioning years of accepting the received wisdom of timing on hills, perhaps we should now start examining our downhill speed.

Willie Naismith, of course, left the subject of descents out of his original rule, and it was only subsequent adjustments to  this that have introduced what may by a fundamentally incorrect variation. Perhaps the Victorian mountaineer was right.

However, we will need to set a default value for our route planning and mapping system. So what are your experiences? We’d like to know. Do you hit the throttle coming downhill, or do you, like us, probably take smaller steps to improve your braking, and take a bit more care not to let gravity overtake you?

You can use the comment box below to let us know, and share you knowledge with other grough readers who may be wondering why that five-hour walk inevitably seems to take an hour longer.