What muscle groups are used in triathlon?

Swimming Biomechanics

The swim is typically completed as front crawl or freestyle. Every individual will have a different technique based on their intrinsic biomechanics. You predominately need a strong core with good shoulder rotation for the key components of swimming.

Strong Core

This is more than getting a six pack! Strong abdominals will help stop you flexing in the middle, creating drag. A strong core also includes your obliques (down the sides) which will prevent your body from wiggling through the water. A strong back will also help to stop you bending in the middle as it will work to reduce the load on your abdominals.


The rotation of the arm through the shoulder can become impinged. Quite often the subscapularis goes into spasm and restricts rotation, and the pec minor can cause rounded shoulders also limiting movement. Any restriction within the shoulder or elbow can also impinge on the nervous system limiting the movement further as your body tries to protect itself. All swimmers should have their median nerve range tested in a biomechanics assessment.

Thoracic Rotation

The majority of our spinal rotation should come from the thoracic region. An increased range in thoracic rotation will allow better clearance of the water in recovery, and will employ more pull from the latissimus dorsi muscles (lats). Breathing will also become easier with increased thoracic rotation as the head will turn naturally with the shoulders. 


Swimming Biomechanics - Muscle Groups Used

Swimming Biomechanics Conclusion

Although swimming is predominately a technique based sport there are areas you can improve through strength and conditioning. An assessment from a Biomechanics Coach will help to pinpoint any asymmetry or imbalances to free up your body’s capacity to swim to it’s full potential.

Focusing on a strength plan covering core work including your obliques and lower back will help to keep your body taut and will reduce drag in the water. 

Increasing your range of thoracic rotation will allow better rotation through the water, it will employ larger muscles during the catch and pull phase and also allow better clearance during the recovery phase. Thoracic rotation will also allow easier breathing without disrupting your stroke.

For the shoulders if the pec minor is in spasm you will often present with shoulders rounding forwards, this will need to be released and strength exercises for the scapular retractors, elevators and rib depressors will need to be undertaken to release it’s load. If subscapularis is impinged then releasing and strengthening the shoulder abductors and external rotators will be required as an initial S&C plan for swimming.

Cycling Biomechanics

The demands on your biomechanics in cycling is similar regardless of whether you’re on a road bike or TT bike. You predominately need a strong core, good hip flexors and extensors, and shoulders free from impingement to prevent nerve issues in the hands.

Strong Core

One of the most common complains for cyclists increasing their distance or load, is lower back pain. Although many can correct this with a bike fit, it is also a sign that the lower back is fatiguing. A strong core is a great way to reduce this, in particular focusing on the abdominals and lower back region. Although the lower back might be suffering from fatigue, it could be overworked due to the abdominals not performing at optimal capacity. If you find you rock sideways when pushing a high power you should consider strengthening your obliques as well.


The shoulder muscles can spasm and impinge on the median, radial and ulna nerves that pass through into your arms. This can cause tingling or numbness in your fingers when on the bike for a prolonged period. This can usually be corrected with a bike fit, or by mobilising the nerve/s at fault.

Hip Flexors

Cycling is predominately a hip flexor movement, and assuming a standard saddle height the hips will never be fully flexed or equally fully extended. This can cause tight hip flexors to become an ongoing problem. When running off the bike this can be a severe problem so needs addressing early and before an athlete becomes symptomatic of tight hip flexors and reduced capacity for hip extension.

Cycling Biomechanics - Muscles Used

Cycling Biomechanics Conclusion

Correcting any asymmetry or dysfunction over the weeks after an assessment can create more balanced movement on the bike. When having a bike fit after restoring movement you’ll be at optimal range on the bike for your event and training. 

Numbness and tingling in the fingers is usually nerve related. There are three mobilisation techniques to assist in the correction of these issues depending on which nerve is impeded, also locating muscles in spasm is key to reducing ongoing nerve related issues in the hands and wrists.

Well rounded core strength is essential to provide power and prevent pain on endurance rides. Hip dysfunction can often be identified when a rider is fatigued as they will often lean or bend to one side. This can also be a QL muscle in spasm and would need a biomechanics assessment to identify the source of the problem. Having methods to release tension and tightness in the hip flexors, and strengthening the extensors will allow better movement and resistance to fatigue or injury.


Running Biomechanics

Running is a full body movement and if one joint is not functioning correctly or your body is protecting an injury, it will affect your complete running biomechanics.

Strong Core

A strong core will keep your head and chest up to allow good breathing capacity. It will also allow a strong connection between the upper limbs and lower limbs enabling a more powerful run.

Thoracic Rotation

In swimming you want your hips to rotate in connection with the thoracic spine, however in running you want the two to operate independently of each other. Good thoracic rotation will create more power and improved core function, and allow for an increased lung capacity.

Hip Extensors

Running requires good hip extension for a power drive in the toe off part of your gait. Hip flexion is also required in the mid swing but triathletes typically struggle with the extension involved especially after a long ride on the bike. The sciatic nerve also runs through the hips and will often be impeded by dysfunction within the pelvis, quite often “tight hamstrings” is actually a limited sciatic nerve and should be mobilised correctly.

Feet & Lower Leg

The calf muscles and feet are also key components for running biomechanics. Feet that pronate for too long have a reduction in power and force during the toe off part of the gait, and feet that supinate too early lose their full capacity to shock absorb potentially leading to injury. The calf muscles can end up tight often as a result of compensation for the hip extensors, and tight calfs often quickly cause achilles tendonitis or plantar fasciitis.

Triathlete at Harlech Triathlon

Running Biomechanics Conclusion

Running involves almost all muscle groups, and many can be fatigued when running off the bike in a triathlon. 

Hip dysfunction should be located as a priority as that can impact on all other areas of the body. Making sure a runner has optimal hip function and adequate strength especially in their hip flexors and extensors should see a more robust runner with a reduction of injury potential. Optimal calf strength and flexibility is essential to prevent injury, tight calf muscles can often be attributed to weakness further up in the hip flexors or extensors.

Thoracic rotation should be monitored and worked on, as well as core work. With core work it is recommended to include relaxation and strength techniques for Quadratus Lumborum (QL) as a priority as it is often in spasm and can be a major limiter when running long distance.

A biomechanics coach can assess an athletes propensity to pronate and supinate and diagnose exercises to help improve function within the foot. This can help towards shock absorption or an increase of power, and make a foot more resistant to injury. 

Biomechanics Assessments

Locate & Correct Asymmetry Or Imbalances Within Your Body

I am a level 4 Biomechanics Coach, Level 2 Coach in Running Fitness and a Triathlon Coach. I’d love to help you get faster and smash your next event with a biomechanics assessment.

By locating asymmetry and imbalances in your body, I will provide a 14 day plan to correct them utilising Muscle Energy Techniques (M.E.Ts), stretches, and targeted strength exercises.

If you would like to know more, Contact Me or take a look at my Biomechanics assessment plans.

Jen Coppock
Jen Coppock
Biomechanics Coach
llangollen, North Wales