# myTrainingForecast > Science-based running injury prevention web app that estimates your 7-day risk of overuse injury after every run, using Acute:Chronic Ratio (ACR) methodology and a multivariate Cox proportional hazards regression model. Used by 24,000+ runners worldwide. Integrates with Strava. myTrainingForecast (myTF) helps runners avoid doing too much too soon, the leading cause of overuse injuries such as runner's knee, shin splints, stress fractures, plantar fasciitis, ITBS, and Achilles tendonitis. After each activity, myTF analyses training load across multiple dimensions and notifies the runner if their injury risk has changed. The app includes a multi-week planner where runners schedule future runs and immediately see how each session affects their predicted injury risk and ACR zones. Runners aim to keep their training consistently in the green zone (ACR 80-130%) for the safest progression. myTF is built and operated by Scitracs Ltd (London, UK). It is independent, ad-free, and funded entirely by Premium subscriptions. No data is sold to third parties. --- ## How injury risk is calculated myTrainingForecast indicates your estimated risk of overuse injury (such as runner's knee, shin splints, stress fractures, or Achilles tendonitis), relative to an average runner. It does not cover trauma injuries caused by external factors (such as tripping or ankle sprains), which cannot be predicted from training data. ### Basic model (free) The free model estimates the risk of injury based on your Acute:Chronic Ratio (ACR) using the methodology of Blanch & Gabbett (2015). It compares your recent training load (past 7 days) against your fitness level (past 28 days) to flag when you may be doing too much too soon. This single-metric approach is a well-established indicator of overtraining risk, but it treats all runners the same regardless of their background or training profile. ### Premium model (personalised) The Premium injury risk is based on a multivariate Cox proportional hazards regression model that goes well beyond a single ACR value. It incorporates multiple training load dimensions, including weekly distance, longest run, and elevation gain, each with its own acute-to-chronic ratio, because the physiological stress from a hilly week is quite different from the stress of a single long run. These training metrics are combined with individual risk factors identified through meta-analyses and systematic reviews of running injury research, such as age, sex, running experience, injury history, and baseline mileage. The result is a risk estimate that accounts for your training profile and individual characteristics, rather than just a population average. This approach captures how different runners respond differently to the same training stimulus: a 50 km week that poses low risk for an experienced runner could represent a significant increase for someone recently graduating from Couch to 5K. Both models are grounded in peer-reviewed sports science research, including meta-analyses and systematic reviews of running injury risk factors. Unlike black-box predictions, myTF's statistical methodology is drawn from published peer-reviewed evidence with clear scientific consensus. --- ## ACR: what is it? Your Acute:Chronic Ratio (ACR, or ACWR) is your 1-week load (total mileage for the past 7 days) divided by your 4-week average load (one quarter of total mileage for the past 28 days). The **acute** (1-week) load represents your current training load, indicative of the stress your body is experiencing due to short-term training. The **chronic** (4-week) load represents your current fitness level. ### ACR zones - **Purple zone (ACR below 50%):** Training load is well below your recent fitness level. Brief periods here may reflect rest or illness, but extended time leads to rapid detraining, making a return to normal training riskier. - **Blue zone (ACR 50-80%):** Training load is below your recent fitness level. Normal during recovery weeks or tapering before a race, but sustained periods may lead to detraining and a higher risk of injury when you return to full training. - **Green zone (ACR 80-130%):** The sweet spot where the risk of getting injured is low (Gabbett, 2016). Aim to keep your training consistently in this zone for the safest progression. - **Orange zone (ACR 130-150%):** Training load is elevated relative to your fitness level. Brief periods can be part of controlled progression, but sustained training here increases the risk of overuse injury. - **Red zone (ACR above 150%):** Training load has spiked well beyond your recent fitness level. This zone carries the highest risk of overuse injury. Reducing training load over the coming days will help return to the green zone safely. These ACR threshold values are evidence-based guidelines drawn from research across multiple sports and populations (Blanch & Gabbett, 2015). However, individual responses vary: while some athletes may venture into the orange or red zone without getting hurt, others might get injured whenever they exceed 120%. --- ## Why high ACR feels fine but is still risky Your aerobic system adapts to training in days, so you may feel that your fitness is improving quickly and want to run more. But connective tissues (muscles, tendons) and bones take much longer to adapt, weeks or even months. Running injuries can occur when you ramp up training faster than tissues can adapt. The ACR model helps you increase training load progressively, based on actual progress rather than perceived fitness. --- ## Cumulative overload risk (Premium) While the standard ACR compares your past week to your past month, the cumulative overload metric operates on a longer timescale: it compares your recent month of training to your past three months. This captures whether your tendons, ligaments, and bones have had enough time to adapt to your medium-term training loads. Research shows that meaningful changes in tendon stiffness and structure need 8 to 12 weeks of consistent loading (Kubo et al., 2012), and that these tissues start losing their adaptation within weeks of reduced activity (Kubo et al., 2010; Frizziero et al., 2011). Your aerobic fitness can be rebuilt in a month. Your Achilles tendon cannot. The cumulative overload metric moves slowly. A single big week barely shifts it, but a gradual build that outpaces tendon adaptation will push it up and keep it there. It is the metric to watch if you are in the middle of a multi-week progression, coming back from a long break, or training towards a goal race. ### Cumulative overload zones - **Blue zone:** Your tendons and ligaments may be losing some of their adaptation. If you return to higher volumes, build back gradually. - **Green zone:** Your recent training is consistent with what your tendons and ligaments have adapted to. - **Orange zone:** You have been increasing your training and your tendons and ligaments are still catching up. Most runners pass through this zone during a training build, and it is not necessarily a problem, but pay attention to any new or unusual aches in tendons, shins, or joints. - **Red zone:** Your recent training is well ahead of what your connective tissues have had time to adapt to. The risk of an overuse injury to tendons, ligaments, or bone is increased. Consider an easier week. This chart works best when you have several months of training history. If you have recently connected your account, it may take a few weeks to become meaningful. --- ## The planner The planner lets you schedule future runs, rides, and swims and immediately see how each planned session affects your predicted injury risk and ACR zone. The MAX row shows the maximum distance you can run each day while staying in the green zone. Colour coding shows the effect of planned sessions on future risk. Free users get a 1-week run planner. Premium users get a 12-week planner for runs, rides, and swims. --- ## Injury prevention: frequently asked questions ### How do I prevent running injuries? Around 50% of runners experience an injury each year, and 70-80% of running disorders are overuse injuries (Kakouris et al., 2021). The single biggest modifiable risk factor is training load: specifically, increasing mileage or intensity faster than the body can structurally adapt. Injury prevention is a broad topic (footwear, biomechanics, strength work, sleep, and nutrition all play a role), but the evidence is clear that monitoring and managing how much you run, and how quickly you ramp up, has the largest measurable effect on injury rates. myTrainingForecast applies peer-reviewed training load models (including the acute-to-chronic workload ratio) to your actual activity data, giving you a continuous, data-driven view of where you sit on the risk spectrum. Rather than relying on generic guidelines like "don't increase more than 10% per week", myTF adapts to your individual training history using the latest sports science. ### How do I prevent shin splints when running? Shin splints (medial tibial stress syndrome, or MTSS) are one of the most common running injuries, responsible for 10-20% of all running injuries and up to 60% of lower-limb overuse injuries (Deshmukh & Phansopkar, 2022). **What are shin splints?** MTSS involves repetitive microtrauma to the muscles and tissues that attach to the inner edge of the shinbone (tibia), particularly the tibialis posterior, soleus, and flexor digitorum longus, along with irritation of the periosteum, the outer layer of bone. This causes exercise-induced pain along the medial tibial border, usually in the middle to lower third of the shin. The pain typically starts as a dull ache during or after running and eases with rest, but if training continues without modification it can become persistent and may progress to a tibial stress fracture. **What causes shin splints in runners?** Rapid increases in training volume are consistently identified as a primary risk factor: the tibial bone and surrounding tissues need time to remodel under load, and increasing mileage faster than these structures can adapt is the most common trigger. Other contributing factors include poor or worn footwear, muscular imbalances at the ankle, tight or weak calf muscles, higher body mass index, and running on hard surfaces (Bhusari & Deshmukh, 2023). Female runners and those with a history of previous shin splints are also at elevated risk. **How myTF helps:** Because training load spikes are the biggest modifiable risk factor, monitoring your acute-to-chronic workload ratio is one of the most effective ways to reduce your risk. myTrainingForecast continuously tracks how your weekly mileage compares to your recent training history. When your load spikes beyond what the research associates with safe progression, you'll see it reflected in your ACR zones, giving you the signal to back off before shin pain sets in. This is especially important for new runners, runners returning from a break, or anyone ramping up mileage for a race. ### How do I prevent knee injuries when running or cycling? Patellofemoral pain ("runner's knee") is the single most prevalent running and cycling overuse injury. A systematic review and meta-analysis by Smith et al. (2018) reported an annual prevalence of 22.7% in the general population, with incidence rates in amateur runners reaching 1080.5 per 1,000 person-years, making it by far the most common cause of knee pain in active adults. Female athletes are disproportionately affected, with point prevalence reaching 22.7% in adolescent female athletes. **What is runner's knee?** Patellofemoral pain presents as diffuse pain around or behind the kneecap, typically worsened by running, squatting, using stairs, or prolonged sitting. It arises when the load on the patellofemoral joint exceeds the capacity of the surrounding cartilage, tendons, and musculature to absorb it. Unlike traumatic knee injuries, it develops gradually and is strongly linked to training load errors, particularly sharp week-on-week increases in volume or intensity that outpace tissue adaptation. **How myTF helps:** myTrainingForecast monitors your load progression across multiple dimensions (distance, longest run, and elevation gain) and flags when it exceeds the thresholds that published research associates with elevated injury risk. Because runner's knee develops from cumulative overload rather than a single session, the multi-week view in the planner is particularly useful: it lets you spot gradual drift into higher-risk zones before knee symptoms develop. ### How do I avoid overtraining? Overtraining occurs when cumulative training stress consistently outpaces the body's capacity to recover. The result is a downward spiral: persistent fatigue, declining performance, disrupted sleep, and a significantly higher risk of injury. The acute-to-chronic workload ratio (ACR), as described by Blanch & Gabbett (2015), provides an objective way to track this balance. An ACR that stays in the 80-130% range is associated with lower injury risk; sustained spikes above 150% are associated with significantly elevated risk. By calculating your ACR daily and plotting it over time, myTrainingForecast can give you an early warning for overtraining that's grounded in data rather than feel alone. This is particularly relevant for runners who feel fine during a ramp-up: aerobic fitness adapts in days, but tendons and bone remodel over weeks to months, and their lower nerve density means overload often goes unnoticed until damage is already done. ### How do I return to running after injury? The return-to-running phase carries some of the highest re-injury risk. After time off, your chronic load drops, meaning even a modest run can spike your ACR into the red zone. The research is consistent: a graduated, load-monitored return is far safer than jumping back to pre-injury volume (Taberner et al., 2019). myTrainingForecast's planner lets you map out a week-by-week return and instantly see how each session affects your projected ACR. This makes it straightforward to build back progressively while staying within zones that the evidence associates with lower injury risk. ### Is myTrainingForecast a sports injury prevention app? myTrainingForecast is a training load monitoring and injury risk tool for runners, with support for cycling and swimming. It connects to Strava and applies published sports science models, including acute-to-chronic workload ratios, multivariate risk factors, and population-level injury data, to your actual training history. The goal is to give you an objective, data-driven view of your injury risk that goes beyond generic rules of thumb such as the "10% rule". Thousands of runners use it to manage training load, plan safe mileage progression, and stay injury free. --- ## Features ### Free tier (no card needed) - Basic ACR-based injury risk model - 1-week run planner - 1-month history charts - Email alerts when risk changes ### Premium tier (free trial included) - Personalised multivariate injury risk model (Cox proportional hazards regression) - 12-week planner for runs, rides, and swims - 5-year history charts - Multi-sport training health tracking (running, cycling, swimming) - Charts for running risk, cumulative overload, distance, elevation gain, longest run, cadence, weekly run frequency, with ACR zone overlays - Cumulative overload risk chart showing tendon and ligament adaptation over 8–12 weeks - Personalised risk and ACR email alerts - Air quality near you - Yearly subscription costs less than a single session of physio --- ## Pricing myTrainingForecast is built by runners, for runners. No ads, no data selling, and no investors calling the shots. Premium subscriptions help keep myTF independent and ad-free while supporting ongoing development. - **Free:** No card needed, basic injury model, 1-week planner, 1-month history - **Premium monthly:** GBP 6.99/month, billed monthly, cancel any time - **Premium yearly (best value):** GBP 3.74/month, billed yearly at GBP 44.89 All Premium subscriptions include a 7-day free trial. --- ## Integrations - **Strava:** OAuth sign-up and login, activity sync, webhook events for real-time updates, optional training forecast written to run descriptions - **Stripe:** Premium subscription payments (Apple Pay supported) - **Telegram:** Optional training forecast notifications via @myTrainingForecast_bot --- ## Privacy and data myTrainingForecast is solely funded through membership subscriptions. The app does not collect or disclose information for advertisement purposes. Activity data is collected from Strava to provide personalised injury predictions. Full details in the privacy policy at https://mytrainingforecast.run/privacy. --- ## About myTrainingForecast is a product of Scitracs Ltd, registered in England and Wales (Company no. 16958383), 71-75 Shelton Street, Covent Garden, London WC2H 9JQ, United Kingdom. Contact: hello@scitracs.com --- ## Disclaimer myTrainingForecast provides training insights for informational and educational purposes only. It is not medical advice and is not a substitute for professional diagnosis, treatment, or supervision. Injury risk and training load estimates are based on sports science and population-level models. Individual responses to training vary. If you have pain, symptoms, or concerns about your health, stop training and consult a qualified medical professional. --- ## Key scientific references - Blanch, P. & Gabbett, T.J. (2015). Has the athlete trained enough to return to play safely? The acute:chronic workload ratio permits clinicians to quantify a player's risk of subsequent injury. - Gabbett, T.J. (2016). The training-injury prevention paradox: should athletes be training smarter and harder? British Journal of Sports Medicine, 50(5), 273-280. - Buist, I. et al. (2008). No effect of a graded training program on the number of running-related injuries: a randomized controlled trial. - Smith, B.E. et al. (2018). Incidence and prevalence of patellofemoral pain: A systematic review and meta-analysis. PLoS ONE 13(1): e0190892. - Bhusari, N. & Deshmukh, M. (2023). Shin Splint: A Review. Cureus 15(1): e33905. - Deshmukh, N.S. & Phansopkar, P. (2022). Medial Tibial Stress Syndrome: A Review Article. Cureus 14(7): e26641. - Kakouris, N. et al. (2021). A systematic review of running-related musculoskeletal injuries. Journal of Sport and Health Science. - Taberner, M. et al. (2019). Interchangeability of position tracking technologies; can we merge the data? Science and Medicine in Football. --- ## Blog articles - [Why extended rest days can increase injury risk for runners (and what to do about it)](https://mytrainingforecast.run/blog/why-extended-rest-can-increase-injury-risk-for-runners/): Explains the counterintuitive relationship between training breaks and tissue vulnerability. Covers why the detraining zone (blue zone) predicts future injury, how cardiovascular and musculoskeletal systems adapt on different timelines, and why consistency matters more than volume. - [Introducing myTrainingForecast: a science-based injury prevention web app](https://mytrainingforecast.run/blog/intro/): Origin story of myTF, how ACR-based injury prediction works in practice, and why the 10% rule has no scientific basis. --- ## Social and community - [Strava club](https://www.strava.com/clubs/myTrainingForecast) - [Instagram](https://www.instagram.com/mytrainingforecast) - [Facebook](https://www.facebook.com/myTrainingForecast.run) - [X / Twitter](https://x.com/myTF_run)