Running Mechanics for Clinicians

Original Editor - Mariam Hashem

Top Contributors - Mariam Hashem, Jess Bell, Kim Jackson, Wanda van Niekerk, Tarina van der Stockt, Robin Tacchetti and Ewa Jaraczewska

Overview of Running Injuries

Running-related injuries are prevalent among runners. The incidence rate ranges from 4.2 per 1000 hours of running exposure in recreational runners to 33.0 per 1000 hours in novice runners. Most runners in any year will report an injury. The most common injuries are:

• Patellofemoral pain
• Medial tibial stress syndrome (shin splints)
• Achilles tendinopathy
• Iliotibial band syndrome
• Plantar fasciitis
• Stress fractures of the metatarsals and tibia

*** Most running-related injuries are due to aggregate loading, are chronic and located in the lower limbs.

Male marathon runners reported hamstrings and calf problems, while hip pain problems were common among women. Most of these injuries have a high recurrence rate.

Risk Factors

Running-related injuries are influenced by a combination of factors, including an individual's running/training characteristics, health, lifestyle, morphology, and biomechanics. This highlights the complex, multifactorial nature of injury occurrence in runners.

Frundsen et al. indicated that running excessively before the musculoskeletal structures have developed sufficient tolerance to endure the external loads placed upon them is a significant factor in running injuries.

A 2018 study by Poppel and colleagues found that previous injuries, training volume, and age are important risk factors for running-related injuries. Sanfilippo and colleagues also note that previous injury was the most relevant risk factor for running-related injuries. A 2015 systematic review of 15 studies identified different risk factors for women and men. These are listed in Table 1.

Table 1. Factors that increase the risk of running-related injuries in men and women

Women	Men
Older age	History of previous injury
History of previous sports participation in non-axial sports (e.g. cycling, swimming)	Restarting running
Participating in a marathon in the last year	Running experience of 0 - 2 years
Running on a concrete surface	Weekly running distance between 20 - 29 miles / 32 - 47.8 km
Weekly running distance (30 - 39 miles / 48 - 63.8 km)	Weekly running distance of more than 40 miles / 64 km per week
Wearing running shoes for 4 to 6 months
History of previous injury

Stress Frequency Model

Multiple related factors cause running injuries. A simple injury causation model using the stress frequency curve can help us understand the contributing factors and how to address them in the management plan.

The applied stress and the frequency of application influence a tissue. If the stress and its frequency are below the injury threshold, the tissue will function normally within its capacity. However, if either or both factors exceed the injury threshold, the tissue is more likely to be injured. This explains why some runners may not experience injury for a long time and develop one as soon as they increase their frequency of training, such as training for a marathon.

Considering stress and frequency is important to understand an individual tissue's capacity.

Running mechanics influence the stress applied to the body, the magnitude, type (bending, shear or tension), and the application speed of each foot contact. Assessing running mechanics makes us think about the stressed structure and explains the presented symptoms. For example, landing on toes -forefoot strike- results in greater stress on the Achilles tendon and the calf muscle forces.

Assessing the frequency of running and training volume helps to understand the effect of the accumulated tissue stress. If falling below the tissue's threshold, the likelihood of developing injury will be low and vice versa. A subjective examination can help us understand the frequency, so ask your client about their weekly training and their standard training. How much running do they do? What was the frequency of applied stress before the injury occurred?

The injury threshold is determined by the tissue's capacity to tolerate both the stress and the frequency of the applied stress. Tissue capacity refers to the functional capabilities of a specific tissue to cope with stress type and frequency. A muscle capable of producing a high peak force may tolerate a high stress level on individual foot contact. On the contrary, if the muscle's capability is low, when applying stress with high frequency, the muscle may not be able to cope well, leading to injuries. However, low-frequency, fatiguing stress can cause long-lasting force deficits requiring a recovery period of several days. To translate this into practical application, we should consider adjusting the mechanical pattern or pushing up the tissue's endurance to tolerate the applied load when assessing a runner. Lowering the applied stress by reducing the amount of running can be a method of off-loading the injured tissue while building up the tissue resilience to cope with the functional aspiration.

Clinical Running Assessment Set-Ups

Many common running-related biomechanical patterns can be identified by 2D analysis using inexpensive tools such as a mobile phone or tablet camera. Standardising the assessment method is important for identifying the patterns and ensuring your findings are not due to viewing angles.

Settings:

Tools/equipment: High-speed camera or mobile phone/tablet camera and a tripod.

Distance: 1.5-2 meters from the treadmill

Height:0.8-1 meter-pelvic height

Views: side (saggital) and rear (frontal)

Timing: initial contact and mid-stance

Joints/regions: thorax, pelvis. hips, knees and ankles.

Follow a structured assessment process by looking at one joint/region at a time. To end up with a structured problem list, slow down the camera's speed to allow you to go backwards and forward and take still pictures to draw lines and identify stress areas.

Common Mechanical Patterns

Bramah et al found that similar mechanical patterns were associated with multiple injuries.

Looking from the saggital plan, we can identify the following patterns:

1. Foot Inclination Angle at Initial Contact: by drawing lines to compare the angle between the sole of the shoes and the treadmill. A great angle indicates greater foot inclination. It can be caused by rear foot strike if the runner's toes are too high compared to the heel, or a forefoot strike when the inclination is mainly due to a high angle at the heel. Neither strike is considered superior to the other. Landing with high inclination will limit the ability to engage in dorsiflexion, which serves as shock absorption. A high-inclined foot will take longer to get the foot flat on the floor to start the shock absorption mechanics, resulting in high impact vertical loading. Fig 3 in the study by Souza RB shows how to identify foot inclination. Conversely, landing with forefoot strike (on tiptoes) allows less time to engage in dorsiflexion utilising the calf complex and possibly stressing the Achilles tendon. Refer to this link to see the difference between different foot strike patterns. In the management plan, a relatively low inclination angle where the foot is low to the ground, regardless of the type of strike (heel or toe), minimises the stress on the Achilles for forefoot runners or engages dorsiflexion for heelstrike runners.
2. Knee flexion angle at mid stance: compare a straight line drawn through femur to the floor to a line from the lateral condyle of femur to lateral malleolus (Figure). A greater angle indicates more knee flexion. Injured runners tend to land with more knee extension at initial contact. This influences tissue stress and the ability to absorb shocks. During running, the knee and ankle function as suspensions. Landing with the knee in flexion and the foot flat engages the suspension spring from when the foot touches the ground. On the other hand, runners with extended knee and high-inclined foot at initial contact are less likely to engage the shock absorption mechanism within the knee and ankle, resulting in higher shocks. This places greater eccentric demands on the quadriceps and is linked to the development of PFPS. The body can respond by compensating on different levels, leading to further complications. From a management perspective, this can be addressed by gait re-education to alter the mechanical pattern and/or eccentric training of the quadriceps to meet the shock absorption demands.

Frontal plane:

1. Trunk side flexion: A vertical reference line is drawn from the midpoint between the posterior superior iliac spines (PSIS). A second line is drawn from this same point to the spinous process of C7. The angle between these two lines represents trunk side flexion, with larger angles indicating greater side flexion. There is no evidence suggesting an associated pathology with increased trunk side flexion; however, it may indicate compensation for a dysfunction in a distal joint. As the trunk shifts greatly side to side, it shifts the body's centre of mass COM. This could result in excessive pelvis drop opposite to the weight-bearing leg. To address this pattern, we need to think of possible causes for trunk shifting as compensation to offload hip muscles by shifting the COM away.
2. Contralateral pelvic drop away from the weight-bearing leg (hip dip): an angle between a horizontal line between PSISs and another horizontal line across the body. Refer to (Figure 3) in this study. Healthy runners show some degree of pelvic drop, ranging from 3-4 degrees, but it's usually controlled. Injured runners demonstrate contralateral pelvic drop compared to healthy runners, which refers to a link between this pattern and multiple injuries. Different compensations can be expected to keep the body's balance as the COM shifts away from increased hip adduction, resulting in different presentations such as ITB, patellar maltracking and/or PFPS.
3. Hip adduction angle: the angle between a horizontal line across the PSISs and another starting at the PSIS on the weight-bearing leg down the central point of the tibiofemoral joint. A greater angle indicates great hip adduction. Losing the gap between the knees indicates greater hip adduction. As a result, the femur will rotate medially underneath the patella, which, in response, will rotate laterally, elevating the stress in the patellofemoral compartment. A runner may develop ITB syndrome as a result of increased hip adduction. Other possible compensations are: rearfoot eversion stressing the medial compartment of the Achilles tendon, increased tibial adduction influencing the bending forces on the tibia.

Key Points

• A stressing mechanical pattern associated with increased training volume (frequency) contributes to the possibility of injury
• When assessing running mechanics, follow a structured method to identify abnormalities
• Always look for obvious patterns. If a mechanical abnormality is not apparent, then it's unlikely to contribute to the presented pathology
• Adjust training frequency initially to offload the stressed tissue while addressing mechanics or building tissue resilience.
• Addressing mechanical patterns by gait re-training will help lower the applied stress and can allow runners to recover from injuries and progress beyond their pre-injury potential
• If addressing mechanical problems wasn't enough to address the pathology, consider building up tissue tolerance to increase its ability to cope with the mechanics.