Avoid Knee Injuries by Balancing Your Leg Strength
Published at 8 May 2019

A balanced approach to leg strength


A closer look at what your quadriceps to hamstring strength ratio is and why the right ratio is important for injury prevention.

Knee injuries are common in athletes across many sports from runners, rowers and cyclists right through to powerlifters and strength trainers. Effective strengthening programmes are often required to improve functional strength and stability. In particular, a deficit in hamstring muscle strength compared to the quadriceps muscle is a precursor to lower extremity injuries. The hamstring to quadriceps ratio (H/Q ratio) refers to the rate between the two muscle groups.

Examples of what the H/Q ratio involves:

1. When kicking a football, as the ball is struck, the hamstring muscles are required to lengthen under load, whilst at the same moment the quadriceps are required to shorten.

2. During rowing action as the seat moves backwards, the hamstrings are lengthening as the quadriceps shorten (and vice versa as the seat moves forwards).

3. In cycling, while the pedal is pushed through the downwards phase, the quadriceps shorten as the hamstrings lengthen. During the upward phase, the hamstrings are shortening whilst the quadriceps are lengthening.

Through all of these muscle relationships, the ratio of hamstring to quadriceps strength is important, affecting the function of the knee joint and risk of injury.

Measuring H/Q ratio

This is most commonly done by using an isokinetic dynamometer - however these are very expensive and only used in high performance facilities. For those without access to these pieces of equipment, you can get a fair idea of your own H/Q ratio using a leg extension and seated curl machines. If you complete a 1 rep maximum test, which is the maximum weight that can be lifted under control, through the full range of movement and without compromising technique. The aim is for the amount the hamstrings can lift be as close to the amount the quadriceps can lift as possible.

For daily life, a healthy knee requires the H/Q ratio to be 50% (i.e the quadriceps can lift 100Kg and the hamstrings can lift 50kg). For athletes that are constantly putting pressure on their knees a minimum ratio of 60% is more desirable. Ratios much closer to 100% can help prevent knee injuries and also reduce the risk of hamstring strain.

Exercises to build a better H/Q ratio

Exercises that work multiple joints and muscles at the same time are effective for improving the muscle balance around the knee. These are referred to as ‘closed kinetic chain’ exercises where the foot is engaged with a fixed surface. These are different to doing leg extensions and leg curls as they promote co-contraction (where both hamstring and quadricep muscles are working at the same time to share the same load).

Some good co-contraction exercises are:

1. Single leg Romanian deadlift (raising one leg straight behind you and keeping the other foot flat to the floor)

2. Side stepping with a resistance band (using an elastic resistance band just underneath your knee and side-stepping as far as you can go)

3. Sideways or forward hops (ensure you fully fix your whole landing foot to the floor before hopping again).

For focussing just on your hamstrings Nordic Curls is a great exercise to try (ask someone to apply pressure on your ankles whilst kneeling up and lean forward, keeping your body straight, as far as you can manage!)

Key points

1. It is essential to restore muscle balance in the hamstring and quadriceps muscles following a knee or thigh injury. This not only provides functional stability to the knee to prevent further injury, but also helps to optimise the performance of the thigh muscles.

2. A H/Q ratio of 50% is fine for daily living activities but for any athletes, regardless of sport, if you put any pressure at all on your knees you need to aim for at least 80% H/Q ratio.

3. If you have sustained knee injuries previously you need to aim for a 100% H/Q ratio to provide an increased level of stability for your knee to prevent further injury.






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