Interval training: watch your form if you make it intense!

Over the past twenty years ago, dozens and dozens of studies – many of which we have reported in SPB - have demonstrated the very significant benefits of interval training for developing aerobic and anaerobic fitness in a wide range of athletes and sports [Follow this link for an overview of some of this research]. But while much has been written about the precise benefits of interval training sessions, how to construct effective interval sessions and how to integrate them into an existing training regime, relatively little research has been carried out on how interval session might affect an athlete’s movement patterns, either during interval efforts themselves, or in the longer term.

Running gait matters for economy

Good form when running is central not just to the sport of running, but so many other sports where running is a key part of that sport (eg soccer, rugby, basketball hockey etc). A runner’s movement patterns during running (known as form or more correctly ‘gait’, and which includes parameters such as stride length, pelvic tilt, vertical displacement, type of foot strike, ankle pronation etc) really do matter.

The first reason is that a biomechanically efficient running gait means that runners can move efficiently across the ground without wasting energy⁽¹⁾. This results in good running economy, which means that less energy is required to maintain a given submaximal speed compared to a runner with poorer economy. And that matters as studies have shown that having good running economy is an extremely important factor for determining performance, at both elite and recreational levels of competition^(2-5).

As an example of this, running gait and stride patterns are known to significantly affect the peak impact forces experienced by runners during footstrike (see figure 1 below). It turns out that there’s a link between peak impact forces and running economy; lower peak impacts forces in runners have been strongly and significantly correlated with more efficient movement and improved running economy⁽⁶⁾. This is likely as a result of the lower vertical displacements (bobbing up and down movements) that are observed with an efficient running gait, which will help reduce impact forces upon footstrike.

Running gait and injury

A second reason to think about running gait is injury – or more precisely, injury prevention. Although no two running gaits are identical, when running gaits deviate excessively from the norm, or become too asymmetrical, injury risk is increased, which also explains why gait retraining programs can be successful at reducing the risk of injury in runners⁽⁷⁾.

As an example of how running gait/style can influence the risk of injury, consider that peak impact forces during footstrike are known to be an important factor for the risk of lower-limb injuries in runners (higher impact forces are correlated with an increased risk of injury)⁽⁸⁾. Now let’s look at data from a study that compared two quite different running gaits: forefoot and rearfoot striking⁽⁹⁾. You can see in figure 1 that the impact forces that the knees and hips of runners had to absorb were much higher when a rearfoot strike pattern was used compared to a forefoot strike pattern (and also when barefoot running, which encourages a forefoot strike pattern). Of course, this doesn’t mean that all rearfoot strikers are injury prone and all forefoot strikers are not – far from it. But what it does show is that running gaits and styles can play a role in determining injury risk.

Figure 1: Power (impact) absorption differences between rear foot, forefoot and barefoot running