is it safe to run every day?

Running is a great form of exercise that has numerous benefits for our health. For instance, people who consistently run at least an hour a week throughout their lives tend to live three years longer and have fewer chronic illnesses, compared with people who don’t do any exercise.

But some people are taking their love of running up a notch – running every day for as many days in a row as possible. This trend is being referred to online as a “run streak”. The rules of the run streak trend are simple: runners must complete a minimum of one mile (1.6km) every day, either on road, trail or the treadmill.

There are some remarkable streaks currently ongoing. Jim Taylor is said to have the longest streak among runners in Britain, having completed at least a mile a day for over 30 years. Globally, the longest streak is held by Jon Sutherland, a US runner who has reportedly run at least mile a day for over 50 years.

These are certainly incredible feats – but what are the effects on the body of running every day? Is it actually safe?

Whether you’re an amateur or professional runner, in order to get fitter you need to follow a training regime that places just the right amount of stress on the body so it can adapt. This is usually done through low-intensity runs and interval training, followed by periods of rest.

When this cycle is consistently repeated over months, runners will notice many changes in their fitness. These include a 5%-10% improvement in maximal oxygen consumption (the maximum amount of oxygen the body can use and transport to its working muscles), reduced heart rate during low-intensity runs, and improved ability to use fat for energy. All of these improvements help runners get faster or run further with less fatigue.

But a key element to becoming a better runner is taking rest periods. This allows the joints and ligaments to recover from the stress that running places on them. Rest also permits the body to replenish carbohydrate stores in the muscles, ensuring the body has energy for subsequent training days. Rest days can also help improve a runner’s recovery time between workouts.

But the nature of the run streak trend means there are no days off. This could have many potential pitfalls that runners should know about.

Continual training without adequate rest can cause many harms to the body. In extreme cases – such as ultra-endurance running – mild scarring of the heart can occur.

It can also weaken the immune system by reducing the function of immune cells. This can increase risk of respiratory infections and cause drastic changes in hormones, such as an up-to-40% reduction in adrenaline and testosterone. This may lead to poor recovery between runs and symptoms of overtraining – including changes in mood or muscle damage.

Runners must also be mindful of potential overuse injuries. These affect up to 70% of elite and recreational runners and could derail a run streak. One of the leading causes of overuse injuries is poor hip-muscle stabilisation in runners. This type of injury is more likely to happen as the training volume increases.

Is there a safe way to run every day?

To complete a run streak safely, pay attention to your training load – a combination of the volume, frequency and intensity of your workouts. It’s pivotal to manage this – taking particular care with the intensity of your runs, since the frequency of training is daily and the duration of runs is at least one mile.

High-intensity runs – such as intense sprint intervals – place more stress on the body and take longer to recover from, compared with low-intensity runs.

There’s also a window when the immune system is suppressed after high-intensity running of up to two hours. Keeping most of the runs easy will not only help you stay consistent, it will also reduce the chances of illness and injuries.

When starting a run streak, consider simply completing the minimum distance required (one mile per day) before gradually increasing the amount of running you do.

If you’re worried about taking days off, active recovery may be useful. This involves doing light exercise on your easier run streak days – such as a very light jog. Or, if you’re willing to break your streak but don’t want to take time off from exercise, you could always go for a brisk walk instead. This allows muscles to recover from the stress of running and can reduce muscle soreness.

Rest days are still strongly recommended, however. Even elite runners have periods away from running or incorporate rest blocks during a week of training. In fact, passive recovery) – which involves doing no exercise at all – is generally considered better than active recovery for helping the body to repair itself and adapt to the stress of training.

Not taking any rest and attempting run to every day could also result in obsessive behaviour towards exercise – and in turn, have negative effects on your body. Before starting a run streak, evaluate whether it’s really in line with your fitness goals.

Running is a great way to improve your health, both physically and mentally. But runners should proceed with caution if they’re thinking of going for a run streak, to prevent overtraining and other risks to their health. Keep in mind things such as intensity and be sure to properly fuel after each run. This will reduce the likelihood of injury and health complications, and should ensure a more enjoyable run streak experience.