Broadly speaking, the main leg muscles used in triathlons are the gluteals (bum), quadriceps (front of the thigh), hamstrings (back of the thigh) and calf (lower leg).

　　The gluteals are used to extend your hip when running and walking. The quadriceps are a group of powerful muscles that extend the knee and help to flex the hip. The hamstrings extend the hip and bend the knee and the calf muscles are involved in extending and stabilising the ankle.

　　What do the glutes do?

　　In my experience, the most important and often least trained muscle group in the body are the gluteals. They are split into the gluteus maximus (the powerful hip extender) and the gluteus medius and minimus that stabilise the hip.

　　These muscles all work together to extend the hip and externally rotate the leg. It’s the control of rotation that is such an important feature of the glutes, particularly when running.

　　The vast majority of people who come and see me with hip, knee, shin and ankle pain while running, have poor rotational control when standing on one leg or running.

　　Without the control from the glutes, the leg will naturally rotate inwards which generates a huge amount of force through the leg. This can lead to many different overload injuries.

　　Most commonly, medial tibial stress syndrome or shin splints, iliotibial band (ITB) syndrome, patellofemoral pain syndrome and many others.

　　Usually these injuries can be remedied quickly if the cause of the overload is discovered and addressed early on.

　　What causes gluteal weakness?

　　A gluteal weakness can be caused by a number of factors, but one of the most common is prolonged sitting at a desk. As the glutes become weaker, the body will compensate by using other muscles such as those in the lower back and quadriceps instead.

　　This then causes a vicious cycle where the glutes then get even weaker. I often see people doing glute exercises seemingly very well, but without actually using the glutes.

　　These issues can be compounded during a triathlon due to the fact that the running portion is usually done in a state of fatigue.

　　Glute-strengthening exercises

　　These three exercises below will get the gluteals firing and help to ensure that you stay injury-free on the bike and while running. Do 4 sets of 15 repetitions, 3 times a week.

　　1. Hip bridges

　　Lie on your back with your knees bent to 90°. Tilt your pelvis backwards and then squeeze your gluteals to peel your hips and lower back off the ground. This can be made harder by just using one leg at a time.

　　2. Single-leg balance

　　By standing on one leg, your gluteals will be working hard to keep you upright and prevent your leg rotating inwards. Focus on squeezing the outside of your glutes to keep your leg still. Hold for 30 seconds at a time.

　　3. Step-ups

　　Stand with one foot on a chair and the other on the ground. Stand up onto the chair by squeezing the glutes of the leg on the chair and pulling up, rather than pushing off the standing leg.

　　There are many other exercises that you can do to improve your efficiency and help with injury prevention, so it's always worth talking to a physiotherapist or personal trainer if you’re not sure.

　　If you have any concerns at all, with any health issue, seek medical advice from a qualified medical practitioner, whether that's a doctor or physiotherapist.