You are getting stronger in the gym, running further or returning to a sport you enjoy. Your muscles feel ready for more. But what about your tendons?
Tendon injuries can interrupt the activities that make training worthwhile. Looking after tendons means thinking about more than the weight on the bar. The speed of movement, number of repetitions, demands of your sport and changes in your training all matter.
I want to help you build strength and fitness with a plan that prepares you for what you actually do. The research gives some useful guidance, although no programme can guarantee that a tendon injury will not happen.
Five Takeaways to Take into Your Next Session
- Your tendons come to every workout. Look at gym work and sports training together when planning the week.
- Speed counts as progression. Faster running, jumping and sharper changes of direction add demands, even when the weights stay the same.
- Repeatable is progress. Completing a familiar session well gives you a useful foundation for the next step.
- Give your comeback a build-up. Start from what you can manage today and reintroduce the demands of your sport gradually.
- Train for the next session, too. Include recovery and review how you respond before adding another challenge.
Muscles and Tendons Work Together
Muscles actively produce force. Tendons connect muscles to bones, transmit that force and, in activities such as running and jumping, help store and release elastic energy.
You do not switch off your tendons when you train muscles. The same exercise can stimulate changes in both. However, an improvement in muscle strength does not measure every aspect of tendon readiness, particularly for a different movement or sport.
In one study, 12 healthy young men trained one leg with heavy knee extensions and the other with light resistance for 12 weeks. The heavier training improved muscle strength and size, increased tendon stiffness and produced tendon growth in some regions. Challenging resistance can therefore be part of tendon training, rather than something tendons must always be protected from. [1]
Here, stiffness means resistance to stretching under force. It is a mechanical measurement, not the stiff or sore feeling you might notice in the morning.
Do Tendons Always Adapt More Slowly?
Different tissues and abilities can change at different rates, but there is no fixed calendar that applies to everyone.
A small study of eight participants found that strength and neural activation improved before some measurable changes in muscle size and tendon stiffness. Another study, involving 20 young and 17 older men, found coordinated muscle and tendon adaptation during eight weeks of training, with some tendon changes detectable after four weeks. Older participants continued adapting later in that programme. [2] [3]
That is more useful than saying muscles take eight weeks and tendons take six months. It also does not support a universal week when a tendon becomes likely to tear. These studies measured adaptation, not a predictable injury window.
For older adults, the encouraging message is that tendons retain the ability to respond to training. The appropriate progression still depends on the person, exercise and recent training history.
Speed Counts as Progression, Too
Think about the force, duration, speed and repetition of the load. These are different features of an exercise, and the number of kilograms alone does not describe all of them.
A 14-week Achilles tendon experiment showed that changing how the tendon was loaded affected the adaptation. A separate 12-week study found that both brief explosive and sustained high-force contractions increased patellar tendon stiffness, although their effects on the wider muscle-tendon system differed. [4] [5]
So there is no basis for saying tendons can only be trained with very slow repetitions or one special type of hold. Controlled strength work is a useful place to establish technique and manageable loading. Faster work may have a place when the activity requires it and the person is prepared for it.
Importantly, most of this research examined lower-limb tendons, often in small samples of men. It cannot provide one perfect prescription for every Achilles, knee, shoulder or elbow tendon.
Strong in the Gym? Build Towards Your Sport
A controlled calf raise and a sprint both load the lower leg, but they are different tasks. Running, hopping and changing direction involve their own combinations of force, loading speed, coordination and repeated effort.
A 2024 study of 20 healthy adults, including 10 women, compared estimated patellar tendon loading across 35 exercises and activities. Different squat variations, jumps and running tasks produced different loading profiles. An exercise name or the fact that it uses body weight does not tell you everything about its tendon demand. [6]
My coaching interpretation is to build strength, then also prepare for the specific demands of the activity. That might mean introducing faster running, landings, repeated accelerations or sport-specific movements gradually. Adding more weight is only one possible progression.
This distinction also appears in rehabilitation research. A trial in 76 people with patellar tendinopathy used a staged programme progressing through holds, resistance exercise, energy-storage work and sport-specific exercise. It improved pain and function more than the comparison programme at 24 weeks. That supports staged rehabilitation for that condition; it does not prove the same sequence prevents tears in healthy athletes. [7]
Make Your Next Step a Manageable One
- Start from your current training. After a break, use what you can manage now as the starting point. Your previous best is useful history, not an automatic starting load.
- Change one main demand at a time. In the gym, that could be resistance, repetitions, sets, range or speed. In sport, it might be distance, sprint count, hills, jumps or session frequency.
- Repeatable is progress. Several manageable exposures give you better information than one good day. Progress does not have to mean a heavier weight every session.
- Consider gym and sport together. A new leg exercise, extra running hills and a jumping class can all add lower-limb demands. Changing activities does not necessarily give the same tissues a break.
- Keep recovery in the plan. Look at demanding sessions across the week, including competition and the exercises you are newly introducing. Recovery needs vary; no fixed number of hours guarantees readiness.
These are practical coaching principles, not a formula that guarantees injury prevention.
An Example for Someone Who Runs and Lifts
Suppose your usual calf exercises and easy runs are comfortable. If you increase calf-raise resistance, you could keep running volume and speed familiar while you establish the new load. When introducing faster running later, keep the strength work stable initially rather than increasing everything together.
The same planning question applies to other sports: what new demand am I adding, and what am I keeping familiar? Consider the force and repetition of your rowing or cycling sessions alongside gym work, rather than assuming every session has the same tendon demand.
Check the Morning After
A simple training record can be useful. Note the exercise or sports session, what changed, how it felt and how normal movement feels afterwards and the next morning.
Increasing localised discomfort, morning stiffness, declining tolerance or a change in how you move is a reason to review the load and seek advice if it persists. General muscle soreness alone cannot tell you whether a tendon has been injured.
For runners, monitoring individual sessions also matters. A 2025 study following 5,205 runners found higher overuse injury rates when a run exceeded the longest run in the previous 30 days by more than 10%. This was observational evidence about running distance, not a universal progression limit for weights or other sports. [8]
Tendon Pain and a Tear Are Not the Same Thing
Persistent tendon pain needs assessment; it does not automatically mean a tear. Nor can training records or pain monitoring guarantee that a tear will not occur.
See a physiotherapist or GP for recurring or worsening pain, swelling, weakness or symptoms that interfere with everyday activity or sport. Stop and seek urgent medical assessment for sudden severe pain with a pop or snap, or loss of normal function. [9]
A painful tendon also does not always need complete rest. Current guidance for diagnosed, nonacute midportion Achilles tendinopathy supports individualised loading and continued activity within tolerance. That advice is condition-specific and should not be applied to a suspected tear. [10]
Train for the next session, too. I want training to leave you better prepared for the activities you enjoy. Keep building strength, give new demands time to become familiar, and get help with symptoms that keep returning. There is room for challenging training and patient progression in the same plan.
Research and Further Reading
- [1] Kongsgaard et al. (2007). Region-specific patellar tendon hypertrophy following resistance training.
- [2] Kubo et al. (2010). Time course of changes in muscle and tendon properties during strength training and detraining.
- [3] Quinlan et al. (2021). Muscle and tendon adaptations to moderate-load eccentric versus concentric resistance exercise in young and older males.
- [4] Bohm et al. (2014). Human Achilles tendon plasticity in response to cyclic strain.
- [5] Massey et al. (2018). Tendinous tissue adaptation to explosive versus sustained-contraction strength training.
- [6] Scattone Silva et al. (2024). Patellar tendon load progression during rehabilitation exercises.
- [7] Breda et al. (2021). Progressive tendon-loading exercise therapy for patellar tendinopathy: a randomised clinical trial.
- [8] Frandsen et al. (2025). Identifying high-risk running sessions in a 5,200-person cohort study.
- [9] Healthdirect Australia. Tendinopathy: symptoms and assessment; when an injury needs urgent care. NHS. Sudden pain and signs of possible tendon rupture.
- [10] Midportion Achilles tendinopathy clinical practice guideline (2024).
General training information, not a diagnosis or an individual rehabilitation programme.
Catherine Ashley