Friday, 10 October 2014

Nutrition, Exercise and Survival in an Extreme Environment: Scott, Wilson, Bowers, Oates and Evans of the Antarctic in 1911-191

As a result of my blog posts on the search for Emperor Penguin eggs that continued for decades in the 20th Century, I have been reading more and more about Scott, Amundsen and Shackleton and their expeditions. Every schoolboy knew the bare bones of the stories of the fatal end of Scott’s party and of how Amundsen got to the South Pole first. Indeed the memory of Captain Oates is evoked regularly but irreverently on the golf course as one of our party trudges off gloomily into the deep rough muttering to his companions, ‘I may be gone for some time’.

A few years ago I tried to get some impression of Scott from Fiennes’s book Captain Scott but I found it unreadable and quickly gave up. It was with some trepidation that I worked my way through hagiographies from the 1920s and 30s, the attempted demolition of Scott and all his works of the 1980s and 1990s, and the more balanced accounts of the 21st Century. The best is Apsley Cherry-Garrard’s (who was with Wilson and Bowers on the horrendous winter journey to the penguin colony at Cape Crozier) The Worst Journey in the World, first published in 1922. Before I started reading on this topic I was aware that the rations for the journey were, with hindsight, markedly inadequate for the energy expended in hauling sledges. I was not aware that scurvy was such a problem.

Scott's party at the South Pole, from left: Oates (standing), Bowers (sitting),
Scott (standing), Wilson (sitting), Evans (standing).
Bowers used a piece of string attached to the camera shutter
I then found the recent essay by Halsey and Stroud, 100 years since Scott reached the pole: a century of learning about the physiological demands of Antarctica, published in Physiological Reviews in 2012. That essay shows plainly just how short the rations fell compared to modern measurements of energy expenditure made by Stroud during man-hauling in Antarctica. It seems that the polar party (Scott, Wilson, Bowers, Oates and Petty Officer Evans) wasted away in their efforts to reach the next and then the next food depot containing daily rations that were themselves inadequate. Add to that the effects of lack of vitamin C, and the unseasonal extreme cold to which the polar party are now known to have been exposed, and it is fairly easy to see how they did not survive.

In 1992-93 on a one-way journey to the pole, Stroud and Fiennes were burning an average of 6,000 kcalories per day. Over a 10-day period ascending to the plateau they were expending nearly 11,000 kcalories per day—that’s over 7 times basal metabolic rate and that, of course, included periods of rest. The rate of expenditure during man-hauling the sledges (10-12 hours per day) must have been extremely high by any standard. By contrast, Scott’s rations provided 4,200 kcalories per day on the ice-shelf and 4,500-4,600 on the summit.

Halsey and Stroud take into account the various factors that would have affected the polar party and the deterioration in their condition that became manifest after those chosen not to reach the pole turned for the journey home across the Antarctic Plateau, down the Beardmore Glacier and across the ice-shelf. Extreme cold, inadequacy of food and water, lack of vitamin C, sleep deprivation and high altitude must have all contributed to the steady and vicious circle of decline of all members of the party, starting with Petty Officer (to distinguish him from Lieutenant Evans—see later) Evans, then Oates and finally Scott, Wilson and Bowers.

I had not previously realised that the polar plateau is so low in oxygen; the partial pressure is only about 510 mm mercury, 30% lower than at the coast and lower than would be predicted from its average altitude of 2,300 m. The effective altitude in terms of the partial pressure of oxygen is about 2,800 m (over 9,000 ft). About 1 in 50 present-day travellers to the Amundsen-Scott Research Station suffer chronic altitude sickness.

Adélie Penguin and chick. Brown Buff, Antarctic Peninsula
26 January 2005
In reading Halsey and Stroud’s account, a few questions came to mind. Firstly, how long does it take the appetite to increase and the gut to adapt and thereby process the amount of energy-dense food needed to match the very high expenditure? Or, if indeed, given the combined effects of cold, altitude and exercise, can any such adaptation be sufficient? Halsey and Stroud noted that some individuals in Scott’s expedition could not  absorb a high-fat diet and that even though they must have been in a state of negative energy balance by Christmas Day 2011, Scott and Wilson could not finish their special dinner. But I can see why those who could not take a high-fat diet did not persist in order to see whether they could become adapted to it; diarrhoea, which a number in the expedition suffered at various times, at an average summer temperature of -25°C does not bear thinking about.

Secondly, what was the importance of the lack of vitamin C on their survival. My impression is that it was more important, perhaps, than some commentators, but not others, have argued. Petty Officer Evans’s initial decline appears attributable to scurvy, from the malaise and lethargy to the lack of healing. In this respect, the condition of Lieutenant ‘Teddy’ Evans (later Admiral Lord Mountevans), one of the Last Supporting Party which turned for the trek back to the coast on 4 January 1912, is worth noting (Halsey and Stroud concentrated on the five members of the polar party). He became ill, clearly of scurvy, with obvious signs by 22 January and only got back to recover because of the truly heroic efforts of his companions, Petty Officers Crean and Lashly and then the medical care given by Atkinson. Lieut. Evans and Petty Officer Evans (according to the reference to Fiennes for the latter in Halsey and Stroud) were averse to eating raw or nearly raw meat, unbeknown to them their only source of Vitamin C. However, the concentrations of Vitamin C in muscle meat are very low any my guess is that lightly-cooked meat from the ponies killed and left at their supply depots would have provided the merest smidgeon of ascorbate. Much has also been made of the absence of the classic clinical signs of scurvy in the polar party but there could well have been subclinical effects at work. In trying to find evidence on the latter I have been bedevilled by the plethora of claims from the dietary supplements industry, quacks and conspiracy theorists.

But there is more that can be added to this story. Dogs were used by Amundsen and by Scott, and ponies by Scott. Neither species needs exogenous vitamin C but both were underfed. The dogs were often driven, like the ponies, to complete exhaustion*. Amundsen saved his men from the fate of Scott’s man-hauling party at the cost of 41 of his 52 dogs used to pull the sledges to the Pole and back.

Halsey and Stroud conclude their essay by considering whether current physiological knowledge and technological advances would protect present-day man-haulers on a similar journey to that nearly completed by Scott in 1911-12. They conclude that they would not:

…the return journey to the South Pole from the Antarctic coast is only just within reach for the most capable of people. The four-month summer window each year, during which man-haulers must inevitably pull insufficient food in environmental conditions that conspire to induce rapid wasting, today still represents an enormous, potentially life-threatening physiological challenge.

While Halsey and Stroud provide a cogent explanation for the gradual decline of the polar party with time, I think they could have made more of their statement:

This cycle would have been accelerated during the final weeks both due to dehydration because of reduced resources to melt water and due to the unusually cold temperatures that they suffered during February and March; these would have served to further decrease pulling power, and increase the energy costs of sledge-pulling due to the friction of snow when below around 􏰀30°C 

Susan Solomon's† analysis of the weather records to me at least indicates the reason for the failure of the polar party (except of course for Petty Officer Evans who had already died, and possibly for Oates who already had, but did not report, frostbite that eventually limited his mobility) to reach safety. On the Ross Ice Shelf the weather was very cold, much colder than a few weeks earlier and much colder than average. Apart from the direct effect of the cold, the deterioration in the surface conditions meant that the huge effort of hauling a sledge did not translate in the coverage of sufficient distance each day. As frostbite in Oates and, eventually, Scott, supervened, the vicious circle of decline accelerated rapidly.

All writers on the fate of the polar party are left with the question of whether Bowers and Wilson could have survived had they left Scott in the tent who by then had a badly frost-bitten foot. I think the odds were on their survival, heavily in the case of Bowers, slightly less so for Wilson. Why they did not opt for a push to the depot is, though, a question best left to those with expertise in group psychology. My reading of it is that both found it impossible to leave Scott.

The relatively rapid end to the hopes of Scott and his party is well summed-up by Susan Solomon and Stearns in their concluding remarks to their paper in PNAS:

The observations of the extremely cold temperatures reported by Scott and his companions in March of 1912 do not imply that these frigid conditions alone caused their deaths. Indeed, one man perished before these challenges were encountered and another was already suffering from frostbite, as has been noted. But the unusually cold temperatures that prevailed over an extended period of several weeks substantially contributed to the tribulations faced by Scott and his team during the final stages of their battle for survival. In spite of their plight, the party continued to record the scientific data that provide key information regarding their fate. Those measurements show that they endured minimum temperatures more than 10°F lower than the average that can now be derived from multiple years of automated measurements for the period from February 25 to March 19 near 80°S on the Ross Ice Shelf. On some particular days in March, the daily minimum temperatures in 1912 were more than 20°F colder than the climatological average. These conditions likely contributed to frostbite and extreme fatigue in the men, as well as to the friction of the very cold snow surface that amplified the physical demands of the strenuous task of man-hauling their supplies by sledge, and thereby slowed their progress. Scott and his last two companions died near the 29th of the month, after enduring what might be dubbed “the coldest march.”

On reading the various suggestions—which often turned into assertions—of the causes of the loss the the polar party, writers have tended to promote a single cause while dismissing others. My firm impression is that it what was not a case or either/or but of a combination of circumstances that formed the perfect storm of a positive feedback loop, with the weather accelerating that final phase, and the descent, to mix metaphors, into a never-ending bottomless pit.

The Coldest March. 2001. Yle university Press. Solomon S & Stearns CR. 1999.On the role of the weather in the deaths of R. F. Scott and his companions. Proceedings of the National Academy of the USA 96 13012-13016

*In this respect it is interesting to note the studies on Alaskan sled dogs covering 490 km in a race over 70 hours at -35 to -10°C; their energy expenditure was an enormous 11,200 kcalories/day.

South Shetlands. Livingston Island from Half Moon Island
27 January 2005