Sports Science Support on Mount Kilimanjaro - Part 3
After breaking a Guinness World Record for the highest altitude game of football, Dawn Scott of the US Women’s National Team has been sharing a series of posts on the journey up Mount Kilimanjaro. In part one, Dawn talked about the preparation for the once in a lifetime challenge. In part two, she described the final part of the climb plus the record-breaking game itself. Here, in the third and final part of the series, Dawn shares some of the data collected during the challenge to help monitor and support the well being of the athletes and staff taking part.
Whilst the euphoria of what we had achieved started to sink in, I spent the last night in the hotel decompressing, cleaning up, refueling, as well as chasing down GPS vests, wellness questionnaires and deactivating the Readibands (sleep watches) loaned to us by Amy Bender from the Calgary Center for Sleep and Human Performance. Readiband tracks 3D movements of your wrist 16 times per second, then uses patented algorithms to process the measurements and identify sleep/wake periods, quality of sleep and quantity of sleep. Readiband is the most accurate, scientifically-validated system in the world for measuring sleep outside of a clinical sleep lab. The key monitoring tools used throughout the climb were:
- Daily wellness questionnaire
- Daily resting heart rate and oxygen saturation using a pulse oximeter
- Readiband to monitor sleep duration and quality
- Catapult GPS to measure external load during the 3 matches:
- 11 v 11 Practice match v Arusha All-Stars (4,551ft.)
- 7 v 7 Practice match (12,500ft.)
- Record breaking match at Kibo Crater (18,871ft.)
As outlined in the previous articles, as altitude increases, the total barometric pressure and partial pressure of oxygen decreases, resulting in hypoxia, which may be associated with decreased exercise performance, increased ventilation and symptoms of light-headedness, fatigue, altered perceptions and sleep disorders. Although the risk increases with altitude, some susceptible individuals may experience symptoms of altitude-related illness beginning as low as 2,500 m (8,200 ft.), which was the height we reached on our first day of trekking. Every year, nearly 1,000 people are evacuated from the mountain, and around 10 deaths are reported. Indeed, a group including the former Premiership referee Mark Halsey, who were attempting to break the record we had set had to abandon their effort as the weather changed once they had reached the summit and resulted in one person being rushed to hospital and two deaths in the group (https://you-are-the-ref.com/mark-halsey-kilimanjaro-diary-day-8-11/). Approximately 40% (12,000) of Mt. Kilimanjaro’s climbers turn back before making it to the summit, so the advice from the guides throughout the trek was imperative for success in terms of reaching the summit and completing the match.
Figure 1 shows a summary of the average self-reported RPE (rate of perceived exertion) and subsequent training load for each day. Day 1 was the warm-up match at the basecamp, and the majority of players completed 45-minutes only, so the overall training load was low for that day in comparison to the other days, which also included hours of trekking. Day 2 involved a drive to Londorssi Gate to start the trek, again involved a gentle start to our first camp up to the mountain. From day 3 onwards the RPE gradually increased until a large jump on day 8 with an average RPE of 7.4, and TL of 3335. For days 9 and 10 the RPE decreased again with concurrent reductions in overall training load.
Figure 2 shows a summary of the average ratings of fatigue (rated from -3 very tired to +3 very fresh) and incidence of headaches for the 30 participants (26 players and 4 referees). As can be seen the average rating for fatigue dropped on day 4, which was the day after the level of altitude had increased to levels that can cause symptoms of AMS. The ratings of fatigue improved for the next few days once players had become more acclimatized and adjusted to the level of altitude. There was another large drop in fatigue on day 8, which was the day we trekked to the crater to play the record breaking match (http://www.guinnessworldrecords.com/world-records/483599-highest-altitude-game-of-football-soccer-overall ), and then on to the summit, reaching an altitude of 19,340 ft. The fatigue rating for day 8 was more linked to the 3am wake up and departure (as players completed the wellness as soon as they woke each day), whilst the continued lower rating on day 9 was more due to the fatigue associated to the exertions of the previous day including the trek as well as the 90-minute match, and the highest training load as shown in Figure 1. On day 9, fatigue improved again as the level of altitude dropped on days 9 and 10 leading to less symptoms related to AMS. The average incidence of headaches (one symptom of AMS) followed a similar pattern and increased from day 1, reaching a peak on day 8 (the summit and match day) before dropping again on the 2 days descending back down to the base camp.
The incidence, and severity, of symptoms related to AMS are shown in figures 3a and 3b. As can be seen appetite and headache (Figure 3a) followed a similar pattern with an increase in incidence from day 1 before a drop on day 7, and then a spike on day 8, whereas for some players appetite was still affected on day 9. Recalling those days, after returning to camp on day 8 dinner was served at around 7pm and 2 of our group missed dinner due to severe symptoms of sickness and headache, and the rest of us ate in silence before heading straight to our tents to sleep, the exertions and effect of altitude taking hold. Figure 3b shows a similar pattern with the incidence of those symptoms being less severe on day 8. Nausea and co-ordination were the symptoms which the players felt were the most severely affected on day 8.
Following the first day of hiking on day 2, at dinner, and every day for the rest of the trek, the guides would record our post-prandial resting heart rate and oxygen saturation measured from a pulse oximeter. Figure 4 shows a summary of those values. As can be seen days 2 (first day of trekking) and 9 (final day of trekking) were very similar with average heart rate and oxygen saturation being 81.2beats/min; 92.7% and 80.5beats/min; 93.2% respectively. This suggests that the physiological status of the players returned to their starting levels by the end of the trek, which I feel shows good adaptation and subsequent recovery from the trek and match demands. Similar to some of the wellness and AMS measures, the heart rate characteristics followed a similar pattern with increasing heart rate/decreasing oxygen saturation during days 3-5 due to decreased availability of oxygen. Both measures recovery slightly on day 6, which was at a very similar altitude as day 5, before again increasing heart rate/decreasing oxygen saturation on days 7 and 8, with both values being the most affected on day 8, as would be expected due to the exertions that day. If any individual’s saturation dropped below 80% they were closely monitored and held out from any extra walking/activity done each day.
Obviously with the data shown thus far being presented as averages, this does not fully highlight the physiological responses of individual players. Figure 5 shows the daily rating for fatigue for three different players, who showed very different responses throughout the 10 days. Player 1 started off feeling ‘very fresh’ for the first 4 days, before dropping slightly and then significantly on days 7 and 8 (very tired). Player 1 was the only player not to make it to the crater for the match. Player 2 was a bit more erratic, but always stayed above 0 (neutral). This player did experience some feelings of nausea/headache during days 3-5 and took medication to counter that. Player 3 felt tired for the first 2 days (she had crossed 8 time zones), showing recovery up to day 7 prior to decreasing fatigue on days 8 and 9 again related to the trek to the summit, match and lack of sleep. She then recovered on day 10.
From the heart rate information (Figures 6a and 6b) it can be seen that Player 1’s heart rate had the biggest increase on day 4 and remained elevated for most of the trip, her oxygen saturation showed a similar pattern with a decrease from day 2 and a significant drop (72%) on day 7 with the medical advice that she should not attempt the trek to the summit for the match. Player 2’s heart rate did not seem to change too significantly, however her saturation was a bit more erratic, with a drop from day 3 to day 4, then a spike on day 5 prior to a large drop on days 6-8. This player had discussions with the medical team in terms of whether she was physically prepared to do the summit hike. It was agreed she could attempt it and she did and succeeded. Player 3 had the lowest heart rate on day 2 (58beats/min), which spiked on day 8 (80beats/min) prior to returning to resting levels on day 9 showing good recovery. Her saturation again followed a similar pattern with a consistent drop to day 7 (79%) prior to increase during the last 2 days.
As part of the daily wellness questionnaire the players indicated their sleep hours and quality of sleep (Figure 7). For the first 3 nights the quality and duration of sleep remained low, which could in part be due to everyone being used to sleeping in tents. Both parameters, on average for the group, increased between days 4-7 which could have been due to a combination of accumulated fatigue from the lack of sleep and the daily trekking (Figure 1) completed, and subsequent need for sleep. On day 8, as has been highlighted previously, as it was such an early start the average sleep and quality of sleep was extremely low for the group. Conversely the next night was amongst the longest and best for the complete 10 days. On average throughout the trek the players self-reported an average of 6.8 hours sleep, with a quality of 0.9 (fairly restful).
Figure 8 shows a summary for the group from the analysis by the Readibands, with the average for the group being 5.4 hours per night, which is slightly lower than the self-reported sleep hours. As can be seen from the overall report (Figure 8) other than sleep latency (onset of sleep), sleep onset and awakenings, all the other parameters of sleep were below optimal. From day 3 onwards the temperature at night ranged from -5 to 5ºC so at times it was difficult to sleep due to those conditions. Conversely due to it being so cold in the evening, following dinner everyone mostly headed to their tents to sleep and would generally fall asleep early, as shown in Figure 8.
Again, examples for two different players can be seen below with player 1 (Figure 9) having much more disturbed sleep than player 2 (Figure 10). As can be seen (Figure 9) the player recorded 3 nights with less than 4 hours of sleep, and no actual sleep was recorded for the night prior to trekking to the summit. The player slept for an average of 5.5 hours each night. Player 2 (Figure 10) slept for an average of 6.9 hours each night and recorded close to 8hours of sleep for 5 nights, and slept for over 9 hours on the night following the summit trek. Her lowest amount of sleep was on the night after the arrival day, again this player had crossed 8 time zones so jet lag and travel fatigue could have affected her sleep initially. Even on the night prior to the summit trek this player seemed to get almost 6 hours of sleep.
The final part of the player monitoring involved the players wearing the GPS units during the 2 warm-up matches and then the actual match at the summit. The difference in the surfaces for the 3 matches means that direct comparison of this data is difficult, as the first practice match was played on grass, the second match was on a sandy, rocky surface and was 7 v 7 due to the space available, whilst the final record match was 11 v 11 on very soft sand. Additionally, the players completed different amounts of playing time, with most players completing 45-mins during the first match (3 players completed 90-mins), the 7 v 7 being 3 x 10mins and eighteen players completing 90-mins in the match at the crater.
Figure 11 shows an average volume (player load and total distance) of the match loads for the players who complete 90-mins. As can be seen the external output for the initial match at the basecamp was much higher than the match at the summit, for both of those metrics. In the NWSL an outfield player on average covers 9.6km and the average Player Load is 1081, although care should be taken when comparing PL between players since this metric is very closely related to the individual player in relation to body characteristics, running mechanics, position, and movement tendencies.
Figure 12 shows a comparison of the higher intensity metrics (high speed distance, number of explosive efforts and peak velocity). As can be seen all of the metrics were higher for the match at the basecamp, with virtually no high-speed running during the match at the crater. This correlates to the peak velocity for both matches, 26km/hr. and 19km/hr., for the basecamp and summit matches respectively. Again, a large factor on those values would have been the surface the matches were played on and inability to build up higher speeds due to ground resistance on foot strike, as well as the impact of the level of altitude. As Lori Lindsey (ex-U.S. Women’s National Team Player) previously said, “I have put my body through some intense physical tests preparing and playing at the highest level but the match at the crater was something else. It was hard to breathe, sprint, recover but at the same time there was something so thrilling and a lightness about it, knowing that we were attempting something that had never been done before.”
During the NWSL, the average for HSR for a player is 635m (324m for the basecamp match), with peak velocities of 32km/hr. obviously the NWSL is a full-time professional league, whilst the players competing in the EPF challenge were a combination of amateur players and now retired former International/professional players, so it would be expected that the physical match demands were lower. Additionally, the basecamp match was still played at 4,551ft. which could also have had a physical impact on the external load for players.
Figure 13 shows a summary for Player 1, who completed the full playing time, for the GPS metrics across all 3 matches. As can be seen the volume (TD, PL, work rate) were much lower for the summit match (match 3). However, the number of explosive efforts the player completed was not as markedly reduced for the summit match. This shows that the player could complete some of those explosive actions, but not necessarily the volume of a 90-min match, with the TD and PL being approximately 50% lower for the match at the summit.
Figure 14 shows the same values for a different player, and again shows a similar pattern for the metrics, external load and subsequent match demands.
In summary, it was an amazing feat to trek to the summit of Mount Kilimanjaro and then enter the Guinness Book of Records by completing a FIFA regulated 90-minute football match. As can be seen the players all had individual physiological responses to the increasing levels of altitude, and residual fatigue from the trek itself, but dealt with it impressively to complete the match at the summit. Symptoms of AMS were present in all players, worsening with increasing levels of altitude, and most players suffered from disturbed sleep with the increasing levels of altitude. Just as impressive was the players returning to their physical resting levels on days 9 and 10 following the summit day. It is more difficult to compare the external loads from the matches, as the surface was different and players completed different amounts of playing time. However, it was apparent that the players could still complete explosive actions at the summit, they were just not as frequent which would be expected at those levels of altitude, less oxygen availability, decreased cardiovascular characteristics, and the accumulated fatigue from the actual trek itself. Considering that many adults do not even complete the climb to the summit of Kilimanjaro itself each year, the fact that only one player in this group did not make it, is I feel in part a testament to the physical and mental resolve of this group of women to complete this amazing record and continue the good work of the Equal Playing Field Initiative.