DURBAN, KWAZULU-NATAL — The 99th Comrades Marathon is set to take over KwaZulu-Natal this weekend, drawing athletes for the grueling 89 km journey from the coast inland. As competitors prepare for the ultimate human race, experts are highlighting the critical uprun tactics, unpredictable weather conditions, and the science behind high-altitude acclimatization strategies that could determine Sunday’s winner.
The 99th edition of the historic race, widely recognized as the oldest marathon in the world dating back to its inception in 1921, will see runners tackling the uprun route from Durban to Pietermaritzburg this Sunday, June 14. The event holds special significance for the running community as it marks exactly one year before the highly anticipated centenary edition scheduled for 2027.
Nick Bester, a former Comrades champion who won the race in the early 1990s and currently coaches the Nedbank running team, notes that while the weather leading up to the event has been windy and highly unpredictable, Sunday is expected to be a great day for racing. Forecasts have fluctuated between rain and clear skies over the past week, but temperatures are predicted to sit comfortably between 13 and 16 degrees Celsius by the time the winners reach Pietermaritzburg.
A major talking point ahead of the race is the distinct physiological and tactical demands of the uprun compared to the downrun. Bester explains that while the downrun from Pietermaritzburg to Durban features massive hills, its predominantly downward trajectory causes severe muscle damage and pain, often leaving runners unable to walk for a week. The downrun typically favors lighter, faster athletes who can handle the impact. Conversely, the uprun requires immense power and strength from the moment the starting gun fires. It favors slightly shorter but stronger runners with powerful musculature, though Bester notes that the recovery is faster, with athletes able to walk again within three days.
Environmental factors also play a crucial role in the athletes’ performance. Bester points out that while Durban is highly humid, Pietermaritzburg is hot but lacks the humidity, presenting a different physical challenge as the runners progress inland.
Perhaps the most complex factor in securing a victory is altitude acclimatization. Bester emphasizes that it is incredibly rare for an athlete living at sea level to win the Comrades Marathon. Top competitors train at high altitudes in the mountains to build red blood cells, which improves hematocrit and hemoglobin levels. When these athletes descend to the oxygen-rich sea level of Durban, their mitochondria are supercharged to carry oxygen through the bloodstream, granting them a significant energy boost.
However, timing this descent is an exact science. According to Bester, runners must race within three to four days of coming down from high altitude. Days four through eleven typically result in a physical lapse for the body. From day twelve onward, athletes feel strong again because the red blood cells generated at altitude—produced at a rate of two million per second and lasting up to 70 days in the body—remain highly active.
While elite competitors meticulously plan this biological window to gain an edge, Bester adds that everyday, single runners generally do not worry about these extreme physiological optimizations and simply focus on completing the ultimate human race.
