As the Berlin marathon approaches, it is important to appreciate the demands such events place on the feet, and the importance of good foot function and footwear to deal with these demands.
MOST MARATHON RUNNERS ARE JOGGERS
The average finishing time of the Berlin marathon is 3hrs and 42min. This equates to a pace of 5.10 min/km and an average speed of 11.76 km/hr (7.31 mph) which is defined in biomechanics literature as ‘jogging’ (Mann and Hagy, 1980). Jogging is a hybrid gait with some elements of walking (long, straight lead leg, rear foot strike, rolling action of the foot from heel through metatarsals to the toes) and some of running (spring-like action of lead leg on loading) (Shrinivasan and Ruina, 2006). As such, the entire foot is loaded during each step and the cumulative load during a marathon is extreme.
DEMANDS ON THE FEET DURING A MARATHON
The force of each landing in running is approximately 2.5 times bodyweight. For a 70kg runner, this is approximately 1,750 Newtons per step. Joggers average 150 steps per minute (262,500 Newtons/minute) making total load over the duration of the marathon (222 minutes) an astonishing 58,275,000 Newtons of force through the feet! Are your feet ready for this?
COMPROMISED FEET AND FOOT INJURIES
The rise in popularity of marathon running has been associated with a rise in metatarsal stress fractures in recreational runners, with excessive foot loading suggested as a causal factor (Bennell et al., 1999). The jogging gait used by most marathon runners is a natural and safe gait pattern at slow speeds (such as average marathon speeds) and on soft surfaces when feet are stable and compliant. Discover more about jogging as a natural gait. Sadly, modern marathons are not run on soft surfaces, and 52-81% of adults have unstable and rigid (subtle cavus) feet (Brewerton et al, 1963; de Oliveira et al., 2018), whose poor shock absorption predispose them to stress fractures (Manoli and Graham, 2017). The increase in pressure under the forefoot from before to after a marathon (Nagel et al., 2008; Willems et al., 2012) explains the predominance of stress fractures in the forefoot region.
HELPING FEET WITH THE DEMANDS OF THE MARATHON
The root of rigid, unstable and injury-prone feet is compromised forefoot structure. To make the demands of jogging a marathon safer, foot stability must be restored and landings must be cushioned. This requires a shoe that is: