Strength training for endurance athletes has become one of the most universally accepted recommendations in triathlon. Every podcast, every forum, and every social media coach seems to agree: you need to be in the gym. But when you look at the evidence and the practical reality of age-group triathlon, the case is far weaker than most people think.
The Opportunity Cost Problem
Most age-group triathletes have somewhere between six and twelve hours a week to train. That time needs to be split across three disciplines, plus recovery. Every hour you spend in the gym is an hour you are not swimming, cycling, or running.
If you have eight hours a week and you spend two of them on strength training, you have just cut your sport-specific training by 25 percent. For an athlete who is still making aerobic gains - which is most age groupers - that trade-off is almost never worth it. The aerobic adaptations you would get from two more hours of swimming, cycling, or running will outperform anything the gym can offer for race-day performance. As I discuss in whether volume is really king, making the hours you have count matters more than adding extra modalities.
What the Research Actually Shows
The research on strength training for endurance performance is often cited but rarely read carefully. Most studies show small improvements in economy - the energy cost of maintaining a given pace or power - but these gains are modest and tend to appear in athletes who are already highly trained and have plateaued with sport-specific work alone.
For the average age-group triathlete who is still improving their aerobic fitness, the marginal benefit of strength work is minimal compared to simply doing more of the sport. The athletes who benefit most from gym work are those who have already maximised their available sport-specific training time and are looking for an additional edge.
There is also an important distinction between strength training for performance and strength training for injury prevention. These are different goals with different protocols, and they are often conflated in the triathlon space.
The Injury Prevention Argument
This is where the conversation gets more nuanced. Strength training can play a role in injury prevention, particularly for runners with a history of specific injuries. But even here, the evidence is not as clear-cut as it is often presented.
Most running injuries are load management problems, not strength problems. They happen because training load increased too quickly, recovery was insufficient, or the athlete was running with accumulated fatigue. Addressing those issues through better programming is more effective than adding gym sessions on top of an already demanding schedule.
If you do have a specific injury history that responds to targeted strength work - a recurring calf issue, a knee that flares up under high run volume - then by all means, include that work. But a general strength program done because someone on the internet said triathletes need to squat is not the same thing as targeted rehabilitation.
When Strength Training Does Make Sense
There are situations where gym work is genuinely valuable. If you are an older athlete experiencing age-related muscle loss, resistance training helps preserve lean mass and bone density. If you have maxed out your available sport-specific training hours and are looking for marginal gains, strength work can provide a small performance benefit. If you have a specific biomechanical weakness that is limiting your performance or causing injury, targeted work makes sense.
But these are specific cases with specific justifications. They are not a blanket recommendation for every triathlete to spend three hours a week doing deadlifts and box jumps.
What You Should Do Instead
If you have limited training hours, spend them on the three disciplines. Get fitter in the water, on the bike, and on the run. Build your aerobic base, develop your threshold through proper sub-threshold work, and work on your VO2 max. These are the adaptations that will make you faster on race day.
If you enjoy the gym and it helps your mental health, keep going. There is nothing wrong with strength training as part of a balanced lifestyle. But do not convince yourself it is essential for triathlon performance when the hours could be better spent elsewhere.
The best use of limited training time is almost always more swimming, cycling, and running. The gym has its place, but for most age groupers, that place is not at the top of the priority list.