New Run (City of Newcastle Running Festival) is fast approaching!
With approximately 2 months left until this event we thought it might be helpful to give you a timely reminder about the best ways to stay injury free as your running loads increase in preparation for your chosen event.
Load vs Capacity
Most running injuries occur when we do too much too soon, after doing too little for too long.
Another way to describe this is with the concept of “Load vs Capacity”
Load is everything you do with a body part. In the context of running, load can be influenced by:
- Running duration/distance
- Frequency
- Intensity/speed
- Terrain (eg. hills vs flat)
Capacity refers to the amount of load you can tolerate. Your capacity may be influenced by many factors including:
- Level of muscle strength and endurance
- Age
- How long have you been doing the activity (training age)
- General health related factors such as sleep, stress, diet and smoking
Most often, running injuries are related to an increase or change in load.
More specifically, injury is more likely to occur when load exceeds capacity.
Load
Dorn, Schache, & Pandy (2012) completed a study which looked at how much load goes through the muscles of the lower limb when running. When looking at the calf and more specifically the Soleus muscle, it has a peak muscle force of around 6.7 x your body weight. This can increase to 8.7 x your body weight at higher speeds. So let’s see this in action…
Imagine an 80kg athlete going for a 5km run
- 6.7 x 80kg = 536kg force through your Soleus with every step
- 5 minutes per KM
- 25 minutes
- Cadence of 180 steps per minute
- 90 steps each leg per minute
- 90 x 25 = 2250
- 2250 steps
- 536kg x 2250 = 1,206,000kg of force through your calf
Now let’s compare that to a 10km run
- 5 minutes per KM
- 4500 steps
- 536kg x 4500 = 2,412,000kg of force through your calf
You’ve just increased the load going through your calf by 1,206,000kgs! This load is something that your body can tolerate most of the time. It is an important reminder however to be mindful of increasing our running load to avoid the load exceeding our capacity.
How do I make sure I don’t increase my load too quickly?
There are a couple of easy ways to make sure you increase load appropriately.
- 10% rule: avoid increasing your weekly load by more than 10%
- Acute: Chronic Workload Ratio which compares your weekly load to the average of the previous 4 weeks
The Acute: Chronic Workload Ratio is a more complex version of the 10% rule but with the same goal in mind. By comparing your current week loading to the average of your previous 4 weeks we can make sure we are not exceeding your current capacity and increasing risk of injury. A ratio of greater than 1.2 indicates an increased risk of injury. A ratio of greater than 1.5 indicates a significantly increased risk of injury. You can find Acute: Chronic Workload calculators available on the internet.
Acute: Chronic Workload Ratio Example
- Week 1: 3 x 10km runs = 30km
- Week 2: 3 x 11km runs = 33km
- Week 3: 3 x 12km runs = 36km
- Current week: 2 x 10km and 1 x 20km run = 40km
Average of previous 3 weeks = 34.75km / Current week = 40km
Ratio = 1.2
What else can I do to prevent running injuries?
Get strong and stay strong!
Strength training has been shown to reduce the risk of sports injuries (Lauersen et al., 2014). If we look at our example from earlier, strengthening your calf muscles will increase their capacity and help with tolerating those millions of kg’s of load we ask of them when running long distances.
Start with checking your calf raise strength/endurance by completing as many single leg calf raises as you can on each leg. Here are some age/gender related normals developed by Herbert-Losier et al (2017).
- 20-29yrs: Males 37 reps, Females 30 reps
- 30-39yrs: Males 32, Females 27
- 40-49yrs: Males 28, Females 24
- 50-59yrs: Males 23, Females 21
- 60-69yrs: Males 19, Females, 19
- 70-79yrs: Males 14, Females 16
- 80-89yrs: Males 10, Females 13
You should also aim for no greater than 10% difference between sides.
Overwhelmed and need some help?
Our physiotherapists can help!
A physiotherapy consultation and assessment is a great place to start if you currently have any niggles threatening your ability to be consistent with your training plan. If you don’t have a training plan, our highly skilled physiotherapists can help develop a plan for you.
References
Dorn, T. W., Schache, A. G., & Pandy, M. G. (2012). Muscular strategy shift in human running: Dependence of running speed on hip and ankle muscle performance. Journal of Experimental Biology, 215(11), 1944–1956. doi:10.1242/jeb.064527
Hebert-Losier, K., et al. (2017). “Updated reliability and normative values for the standing heel-rise test in healthy adults.” Physiotherapy 103(4): 446-452.
Lauersen, J. B., Bertelsen, D. M., & Andersen, L. B. (2014). The effectiveness of exercise interventions to prevent sports injuries: a systematic review and meta-analysis of randomised controlled trials. British journal of sports medicine, 48(11), 871–877. https://doi.org/10.1136/bjsports-2013-092538