As the popularity of running continues to increase, we’re likely to see a mirrored rise in the incidence of injury. Strength training is regularly recommended to runners for a plethora of reasons, including injury prevention. But does scientific literature support this claim? We analyse the available evidence to see whether strength training should be adopted en masse for the purpose of injury-prevention.

Why does it matter?

The benefits of running are well-established. Not only are there innumerable physical health benefits, an increasing evidentiary base exists for the mental health benefits of the sport, a topic covered in a previous article.

Despite the commonly cited benefits, injury is a widespread concern. For example, in a questionnaire sent out to entrants of a major marathon, 287 of 497 respondents (58%) incurred some form of injury during training. 71 of those reported more than one injury. The most prevalent were, understandably, lower limb injuries – 113 involving pain or disability in the knee.

In an additional study examining injury incidence in Australian Army recruits, researchers substituted all running periods of standard recruit training with a weighted march activity. While there was no statistically significant difference in the number of injured recruits, those who underwent typical standardised training (the run group) had significantly more lower limb and knee injuries. What’s more, “injuries in the run group produced more morbidity, with nearly double the number of days of restriction, hospitalisation, and not fit for duty” (Rudzki, 1997).

Understanding how to reduce the incidence of injury in runners is essential if we’re to promote the sport as a healthy activity to be done in longevity. This is particularly relevant in the context of an increasingly sedentary society, where the prevalence of obesity and associated comorbidities is surging at great economic cost (the annual cost of obesity and overweight to the NHS was estimated to be around £19 billion, while lower productivity costs accounted for an additional £16 billion. When individual costs were accounted for, the annual cost of obesity and overweight in the UK was estimated to be a whopping £98 billion).

Strength training is commonly recommended to runners for a plethora of reasons. The National Academy of Sports Medicine (NASM) stresses a number of benefits, from improved balance and joint stability, to improved muscular strength, power, and endurance. Moreover, the NASM advocate for the ability of strength training to reduce the risk of injury by “incorporating strength training that uses new movement patterns and corrects movement imbalances.”

Indeed, in my initial review of Runna, an app-based running training platform, I spoke highly of the company’s integration of strength training (as well as their inclusion of mobility and pilates), assuming an embedded focus on injury prevention.

Recently, however, Nick Gornick, Doctor of Physical Therapy at RebuiltPT, wrote the following on Threads, which got me thinking about the empirical basis of the relationship between strength training and injury incidence in runners:

Strength training can improve your running performance, joint health, and bone health. But the jury is still out on its effect on injuries. I’ve seen plenty of runners with injuries who strength train, and plenty of injuries from runners who don’t strength train. I’ve also met injury free runners who never even think about strengthening. I’ve met runners who may have been injured because they overdid it with their strength training program. The research on the topic is very limited.

Nick Gornick

Consequently, the impact of strength training on injury prevention seems individual and multifaceted. Is there a right or wrong answer where strength training for this purpose is concerned?

While limited, I’ve read the core research papers assessing the impact of strength training on injury incidence in runners, summarising the findings below. This is by no means a thorough literature review, but hopefully this article sparks debate on how best to approach and manage injury.

Literature on the Impact of Strength Training on Injury Incidence in Runners

One commonly cited paper is a randomised study of a strength training program assessing whether the incidence of injury differed between groups of runners participating in the New York City Marathon.

Runners were randomly assigned to either a strength training or observation group. The strength training group received a 10-minute instructional video, accompanied by a handout. The focus was core, hip-abductor, and quadriceps strengthening, with both beginner and advanced tracks available. Participants were asked to complete the program three times per week in the 12 weeks leading up to the race.

On average, participants completed the program twice per week (+/- 1.2). The incidence of overuse injury resulting in marathon non-completion was 7.3% (27/368) in the observation group and 7.1% (25/352) in the strength training group. Minor injuries were reported at least once during the study period by 186 (50.5%) runners in the observation group and 163 (46.3%) runners in the strength training group.

The strength training intervention did not result in a statistically significant lower incidence of overuse injury resulting in marathon non-completion or average faster finishing time. There was a non-statistically significant decrease in minor injury incidence, average pain during the race, and use of the marathon medical tent.

Despite well-intentioned aims to plug evidentiary gaps in literature surrounding the relationship between strength training and injury incidence in running populations, the study was marred by poor design.

The first major concern is the use of an observation group that did not serve as a true control group. Participants in this group were not restricted from independent strength training. Most runners are likely to have heard, or been advised by others, of the multitude benefits of strength training for running performance. As such, it’s highly unlikely that all participants in the observation group restrained from strength training completely. Effectively, rather than comparing a strength training program with its absence and assessing differences in injury incidence, the study may merely have compared the experimental 10-minute program and the observation group’s self-directed strength training.

In addition, compliance was monitored via self-report questionnaires emailed fortnightly to participants. Self-report can be an unreliable method of data collection, susceptible to bias arising from social desirability and selective recall. However, due to the reasonably hefty sample size, we’re not going to be too critical of the authors’ choice here!

Another study of interest is by Niemuth et al. (2005). While not directly addressing the question of this article, we think the findings elucidate the importance of well-designed, individualised strength training programs.

The authors set out to assess differences in the strength of 6 muscle groups of the hip in recreational runners. Comparisons were made between the involved (injured) leg, the uninvolved (uninjured) leg, and a control group of non-injured runners. Among the injured runners, the injured side hip abductor and flexor muscle groups were significantly weaker than the non-injured side. What’s more, the injured side hip adductor muscle group was significantly stronger than the non-injured side.

It’s unsurprising that the muscle groups of an injured side are weaker than their non-injured counterparts. But what explains the significantly stronger hip adductor muscle group in the injured side? It’s certainly difficult to ascertain whether the increased strength was a cause of injury (e.g., due to imbalance) or a consequence of it. But, interestingly, no significant side-to-side differences in hip group muscle strength were found in the non-injured runners.

As I’ve alluded to, Niemuth et al. (2005) were unable to establish a cause-and-effect relationship. However, because participants were the first 32 individuals who met inclusion criteria, recruited via referral from their physicians to a physical therapy clinic with a diagnosis of a running-related overuse injury, one might surmise that the disparity between adductor and abductor strength could have been the cause of injury. We can’t say for sure whether that was the case, but it’s certainly a possibility.

If this is the case (albeit taken with a pinch of salt), the results of Niemuth et al. (2005) lend credence to the importance of reducing muscular imbalances, which strength training can help to address. Rather than it being weakness in the hip abductor that was responsible for injury, the disparity (or imbalance) between the two groups may have played a pivotal role. As the authors conclude:

“Because most running injuries are multifaceted in nature, areas secondary to the site of pain, such as hip muscle groups exhibiting strength imbalances, must also be considered to gain favourable outcomes for injured runners.”

Niemuth et al. (2005)

Implications

While the following is a sweeping generalisation based on somewhat dubious conclusions, Niemuth et al. (2005) may contribute to our understanding of the results of the earlier mentioned study. In the research on New York City Marathon runners, the instructional videos focused, in part, on strengthening hip abductors, seemingly at the expense of the adductors.

While it’s excessive to suggest that this may have been the difference between a statistically significant reduction in injury prevention and the one observed (particularly considering the poor study design), it does at the very least have implications for the design of future strength training programs that appropriately target all related muscle groups.

While I’m not a personal trainer, I personally feel it would be appropriate to conduct pre-training assessment prior to the commencement of strength training to identify areas of weakness or imbalance. Of course, under the constraints of a large scale study like that of the New York City marathon, it’s completely impractical to do so. And while I understand the necessity to deliver strength training via video and accompanying handouts, it’s difficult to assess whether participants are carrying out the exercises with correct form. More than that, is a 10-minute instructional video really sufficient? Whether my above suggestion is a necessity is for those more qualified to chime in on.

Other Considerations

Injuries happen for a number of reasons, some of which are difficult to control for. For example, in a study by van Poppel et al. (2021), previous running-related injuries were the strongest risk factor for additional injuries amongst long-distance runners. Previous injuries not attributed to running were the strongest risk factor for subsequent injuries in short distance runners. Higher body mass index, age, lack of running experience, and lower running mileage were moderate risk factors for short-distance runners. Similar results were found by Kluitenberg et al. (2015), who concluded, “higher age, higher BMI, previous musculo-skeletal complaints not attributed to sports and no previous running experience were related to running-related injuries (RRI).”

So, should runners train strength?

As the quote from Nick of RebuiltPT indicates, injuries happen in runners who strength train. But they also happen in those who don’t, perhaps in equal measure. In some ways, whether strength training reduces the incidence of injury is irrelevant. Of course, if existing research demonstrated dramatic increases in injury rates amongst runners who strength trained, it would be a no brainer. Don’t bother. But existing research doesn’t show this. If anything, we’re at a crossroads. We don’t really know if it helps or if it doesn’t. So long as the evidence stays this way, there are a multitude of other benefits that make strength training worthwhile for runners.

While it’s not within the scope of this article to go into much depth on the additional benefits of strength training for runners, what we do know is it can help improve power and speed. Strengthening our core improves our posture and form (without which, we’re more likely to get injured). Joint stability is improved by strengthening the muscles around them. We even experience a reduced chance of falling (provided a well-rounded approach to strength training is adopted) by incorporating exercises that improve balance and coordination.

In respect of the above, there’s seemingly far more reason to introduce or continue a program of strength training if you’re a runner than to simply not bother for worry of risking injury. Nonetheless, I do think my above recommendation of working with a physical therapist or a personal trainer, thereby gaining an understanding of where your attention is best focused, is likely a good one.

If you’re involved in this industry, whether as a running coach, physical therapist, or personal trainer, I’d be really keen to hear your thoughts on this topic.