If you’ve ever run a hard race, whether it’s over a long distance or perhaps one you did very quickly, you’ll know the feeling towards the end of pure exhaustion. Your limbs might have felt ‘heavier’ and you may not have been able to run ‘normally’. This is because fatigue effects our running gait pattern, or more scientifically, our kinematics.

Fatigue is common in any sport requiring high exertion levels, such as long-distance running, where you need to maintain energy expenditure for long periods of time. Furthermore, since we know that the likelihood of developing a running related injury increases with increased weekly mileage (van Gent, 2007) and lack of running experience (Buist et al. 2010), we can also assume that fatigue plays a role in running-injury risk.  

Scientific studies that have investigated the effects of fatigue on the way that you run are limited, but we will do our best to disseminate what the research has told us about the subject.

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How does fatigue affect running performance?

There is no question that fatigue has a detrimental impact on running performance, and as you get tired your running speed decreases. From a purely biomechanical perspective, running speed is the product of cadence (the number of steps you take per minute) and step-length, and so it is of little surprise that as you fatigue, your running cadence and step-length both decrease (Winter et al. 2017). These changes in spatial-temporal parameters are associated with changes in your kinematics, and so increased knee flexion at foot-strike, decreased hip and knee range of motion,  and increased trunk-lean are observed. It is also likely that your stride-length becomes more variable.

It has been proposed that the reduction in step-length caused by reducing hip extension at toe-off and reducing knee flexion at foot-strike are protective mechanisms for injury and for energy preservation. However, if step-length decreases with no increase in cadence (or if cadence remains constant or decreases), then running speed and thus performance decrease (Storhrmann et al., 2012, Winter et al., 2012).

Run3D investigated the effect of a half-marathon (21 km) on the 3D kinematics of running by comparing the biomechanics of runners before and immediately after the race. In our study, participants were required to run at the same speed both before and after the race, so that we could investigate what changes, if any, occurred when running speed did not change. Significant kinematic changes did occur, and participants ran with increased cadence and knee flexion angle at foot-strike, and decreased stride length and stance time. Although no other systemic alterations were found, further analysis revealed subject-specific changes in joint kinematics. Gait parameters that were outside our control range before the race were worse after the race when the participant was fatigued.

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How does fatigue affect running injuries?

There are certain variables of an individual’s running pattern that are associated with an increased risk of developing a running related overuse injury such as patellofemoral pain, medial tibial stress syndrome and iliotibial band syndrome (Maas et al., 2018; Neal et al.,2016; Aderem & Louw, 2015; Munteanu & Baron, 2011)). Kinematic risk-factors for these common injuries include:

1.      Increased hip internal rotation (Maas et al.,2018)

2.      Increased hip adduction (Willwacher et al.,2020)

3.      Increased knee internal rotation (Willwacher etal., 2020)

4.      Increased rear-foot eversion (Willwacher et al.,2020)

5.      Reduced cadence (Winter et al., 2017)

6.      Increased body rotation (Winter et al.,2017)

7.      Reduced knee flexion at foot strike and during stance (Winter et al., 2017)

As fatigue sets in, our ability to maintain our trained kinematic movement patterns becomes affected, with our bodies adapting top reserve energy. Whilst this tactic helps us reach the finish line, it increases our injury risk and decreases running speed. In our study of runners before and after a half-marathon, we found that kinematic injury risk-factors that were identified before the race were worse after the race when the participant was fatigued, thus putting him/her at a higher risk of developing a running related injury.

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Novice Versus Competitive Runners

A recent study by Maas et al. (2018) investigated the effect of a fatiguing run on the kinematics of novice compared to competitive runners. Participants performed two maximal-effort running sessions and 3D gait analysis was used to measure their kinematics. The results were consistent with previous research, and the novice runners showed more significant changes in their movement patterns when fatigued compared to the competitive runners. Specifically, the novice runners ran with increased forward trunk lean, increased ankle plantar flexion and reduced knee flexion in stance after the fatiguing run. Both groups demonstrated increased anterior pelvic tilt and greater hip adduction movement after the run compared to before.

The study confirms that novice runners demonstrate greater changes in the way that they run as they fatigue compared to experienced runners. Interestingly, this coincides with what we know about novice runners having a greater incidence rate of running related injuries compared to experienced runners (Kemler et al., 2018).

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Males Versus Females

Patellofemoral pain is the most common overuse injury in distance runners, and the incidence is higher in females compared to males. The increased incidence has been attributed to anatomical structure and increased loading at the patellofemoral joint in females compared to males (Noehren et al., 2012; Wilson et al., 2015). It has also been proposed that there may be a difference in the way that males and females respond to fatigue, which puts females at a greater risk of developing the condition.

A study in 2015 investigated whether there were any differences in the effects of fatigue on patellofemoral joint loading in males compared to females (Wilson et al., 2015). However, no significant differences were found between the two sexes and the authors concluded that gender bias could not be attributed to any changes seen in running mechanics during an exhaustive running trial. Whilst kinematic changes were observed with fatigue, the changes were consistent between the groups and not only in the females (Wilson et al.,2015)

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What can you do to lessen the impact of fatigue on performance and running injury risk?

There is limited scientific evidence to support ways of reducing the impact of fatigue on running performance and injury risk However, here are a few suggestions that can be deduced from what we do know:  

a.)    Experience: Obviously this isn’t something that can be achieved overnight, but we know that more experienced runners are impacted less by fatigue than novice runners. Make sure you train appropriately for what you want to achieve!

b.)   Step-length and cadence: Speed =step-length x cadence and so if you want to maintain speed, you need to keep the product of step-length and cadence consistent. We found that when runners were asked to run at the same running speed before and after a half-marathon, they ran with reduced stride-length and increased cadence after the race compared to before. So, as you begin to tire and your stride-length begins to increase, focus on increasing your cadence in order to try and maintain speed at the end of a race!  

c.)    Gait analysis and S&C: If you know that you are already predisposed to some of the most common kinematic risk-factors for running injuries (e.g. increased hip adduction, increased knee internal rotation, and increase rearfoot eversion), then you can aim to improve these from their ‘base-line’ state to help slow down the progression into ‘even worse’ as you fatigue. A gait analysis will help to identify detrimental patterns in your running technique so that you can target these areas for improvement.

As we get tired when we run, the most significant and consistent kinematic changes that occur are those associated with reduced running speed: reduced cadence, reduced stride length, reduced hip extension at toe-off, increased knee flexion at foot-strike. Novice runners are more impacted by the effects of fatigue compared to experienced runners, and as far as we know so far, males and females are impacted by fatigue to the same extent.

We have provided some suggestions above on how you can try and reduce the impact of fatigue on running performance and injury risk.

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References:

Chan-Roper M, Hunter I, Myrer JW, Eggest DL, & Seeley MK. 2012, Kinematic changes during a marathon for fast and slow runners. J Sports Sci Med, Vol. 11, pp. 77-82.

Strohrmann C, Harms H, Kappeler-Setz C, & Troster G. 2012, Monitoring kinematic changes with fatigue in running using bosy-worn sensors, IEE Trans Inf Technol Biomed, Vol. 16, pp. 983-90.

Winter, S., Gordon, S., and Watt,K. 2017, Effects of fatigue on kinematics and kinetics during over ground running: a systematic review, The journal of sports medicine and physical fitness, Vol. 57, no. 6, pp. 887-899.

Willwacher, S., Sanno, M., & Bruggemann,G. 2020, Fatigue matters: an intense 10km run alters frontal and transverse plane joint mechanics in competitive and recreational adult runners, Gait and Posture, Vol 76, pp. 277-283.

Neal, B., Barton,C., Gallie,R.,  O’Halloran, P., & Morrissey, D.2016, Runners with patellofemoral pain have altered biomechanics which targeted interventions can modify: a systematic review and meta-analysis, Gait Posture, Vol 45, No. 6. 69–82.

Aderem, J., &  Louw, Q. 2015, Biomechanical risk factors associated with iliotibial band syndrome in runners: a systematic review, BMC Musculoskelet. Disord. Vol. 16, pp.356.

Munteanu, S., & Barton, C.2011, Lower limb biomechanics during running in individuals with achilles tendinopathy: a systematic review, J. Foot Ankle Res. 4 (2011) 15,

Buist, I., Bredeweg, S. W.,Bessem, B., van Mechelen, W., Lemmink, K. A. P. M., & Diercks, R. L. ,2010,  Incidence and risk factors of running-related injuries during preparation for a 4-mile recreational running event. British Journal of Sports Medicine, Vol. 44, pp. 598–604

van Gent, R., Siem, D., van Middelkoop, M., van Os, A. , Bierma-Zeinstra, S, & Koes, B. W. 2007, Incidence and determinants of lower extremity running injuries in long distance runners: A systematic review. British Journal of Sports Medicine, Vol. 41, pp.469–480.

Maas, E, De Bie, J., Vanfleteren,R., Hoogkamer, W., Vanwanseele, B. 2018, Novice runners show greater changes in kinematics with fatigue compared to competitive runners, Sports Biomechanics, Vol 17, No. 3, pp. 350-360.

Willson, J. D., Loss, J. R.,Willy, R. W., & Meardon, S. A. (2015). Sex differences in running mechanics and patellofemoral joint kinetics following an exhaustive run. Journal of Biomechanics, 48, 4155– 4159

Schubert, A., Kempt, J., & Heiderscheit, B., 2014,Influence of stride frequency and length of running mechanics: a systematic review, Athletic Training: Sport Health , Vol. 6, No. 3, pp. 210-217.

Kemler, E., Blockland, D., Backx, F., & Huisstede, B.,2018, Differences in injury risk and characteristics of injuries between novice and experienced runners over a 4 year period, The physician and sports medicine, Vol 26, No. 14.

Noehren, B., Pohl, M., Sanchez, Z., Cunningham, T., & Latternamn, C., 2012, Proximal and distal kinematics in female runners with patellofemoral pain, Clinical Biomechanics, Vol 27, No. 4., pp. 366-371.

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