The mistake 80% of runners make and how strength fixes it

When you think of running, the first thing that usually comes to mind is to add more and more kilometers. Fartlek workouts, series at different paces, long runs on the weekend.... That has been the mantra of many popular runners - including me - for years. However, two physical trainers changed my way of thinking throughout my sporting life, Enrique Diez Maestro (national handball coach and doctor in Physical Activity and Sport Sciences) and Antonio Bores (also a doctor in this discipline, with a lot of experience in athletics and triathlon and now working with professional soccer teams around the world). They both convinced me of something that completely transformed the way I train: to take your performance to the next level, you must incorporate strength. Yes, strength. Lifting weights. Are you lazy? I recommend you read on....

I era one of those who thought that getting weights, barbells and squats in might frustrate my running performance, pursuit of agile paces and my lightness of stride. But if you apply the right routine to your training program you'll find that strength boosts your running efficiency, reduces the likelihood of injury and, incidentally, gives you an extra point of power when the session goes uphill or when you need to push in the last few miles of a race. How do you fit it into your running schedule without messing up your best paces? What exercises do you need? How much intensity is just right? Here we look at why strength is so important, how to integrate it without ruining your legs and what tips to follow to squeeze its potential.

Why can strength training change everything?

Running economy

By working on strength, you teach your neuromuscular system to recruit fibers more effectively. In English: to maintain "X" pace, you will use less energy. You will feel that, in a way, you "run easier", your heart rate does not shoot up as fast and your muscles fatigue less at equal effort.

Fewer injuries, more solidity

Every time your foot lands on the ground, there's an impact on joints, tendons and muscles. Strengthening your glutes, quads and hamstrings - in addition to a solidcore - cushions those blows and delays the onset of discomfort or recurring injuries. Anyone who does long runs or trail runs knows how crucial it is to hold on without collapsing physically.

Types of sports injuries you can suffer while running and how to identify them

Final sprint and hill power

Whether you run on the road or in the mountains, there comes a time when you need extra power: an unexpected steep hill or an end of the race that requires a change of pace. A strength plan that includes explosive exercises allows you to face these moments with firmer and more decisive strides.

Doesn't strength really "sabotage" your pace?

Those of us who have been running for a long time have heard a thousand times the debate about the "interference" between strength and endurance. Can't it spoil your running speed, adding fatigue and stiffness? The reality - backed up by recent studies and the experience of coaches like Díez Maestro and Bores - indicates that strength not only doesn't sabotage your paces, but helps you maintain and even improve them... as long as you know how to organize your sessions.

• Adaptation period: atfirst, your legs may suffer if you introduce intense force all at once. It is normal to feel stiffness and, perhaps, a decrease in sensations on subsequent runs. Don't give up; as your muscles adapt, you'll feel less discomfort and enjoy more power.
• Smart planning: place strength training on days when it does not interfere with decisive sets or a key test. We recommend at least 24-48 hours apart before a high-speed or maximum-demanding session.
• Fair dosage: two or three strength days per week may be too much for a beginner. Start with one or two, and adjust as your body responds.

Sample weekly schedule: Combining running and strength

Let's look at a schedule of 5 running days and 2 strength days. Use it as a reference and adjust it to your routines.

Monday

• Morning: Light running (60 min) at aerobic pace.
• Afternoon: Strength focused on upper body and core ( bench press, pull-ups, rowing, planks). Moderate intensity.

Tuesday

Quality running training (speed series or hills). Avoid leg work on this day.

Wednesday

Either total rest, or very gentle regenerative running (30-40 min). Take advantage of this day for stretching and mobility.

Thursday

• Morning: A tempo run (20-30 min at threshold pace) or block of medium sets.
• Afternoon: Lower body strength (squats, deadlifts, lunges). Here you can look for more intensity, leaving a margin of 6-8 hours after the running session.

Friday

Light running for 30-45 min to loosen up, or even rest if you feel too much fatigue.

Saturday

Medium run60 min), at a "happy" pace but without being explosive.

Sunday

Long run, focused on adding miles and endurance. Without mixing strength so that your legs arrive fresh.

Our advice, download the RUNNEA app and train for free with a training program that adapts to you, including strength exercises.

Adapting it to your season

Base phase (pre-season)

This is the ideal time to focus on strength, with 2 or even 3 days a week if your training plan allows.

Work on multi-joint movements (squats, deadlifts, bench presses, pull-ups...) with medium reps (8-12) and progressive volume. Your workouts are usually aerobic, not so intense.

Competitive phase

Reduce strength to 1 or 2 days, with lower volume or looking for explosiveness (few reps, high loads if you already have a base). This keeps your strength adaptation without interfering with speed peaks and demanding runs.

Transition phase

After your target race, you can take the opportunity to resume strength with more margin, polishing weaknesses and balancing muscles. Without the pressure of preparing for a test, you'll explore variations with less fear of stiffness that can ruin a day's series.

If you're a trail runner, strength is even more important.

If the mountains are your thing, strength becomes even more non-negotiable. Long climbs and descents require more quad and glute development, while a solid core ensures stability with a backpack or poles. In addition, trail running usually involves more hours of training and joint fatigue, so preventing injuries becomes key. A couple of strength sessions, focused on hamstrings, glutes and core, will make a difference in your performance on hills and tricky descents.

This is why it is important to include hill sessions in your running training plan.

Essential exercises

• Squats: barbell, kettlebells or dumbbells, depending on your level.
• Deadlifts: conventional or Romanian, important for working the posterior chain (hamstrings, glutes, lower back).
• Lunges: excellent for unilateral stability and running balance.
• Calf raises: protects the Achilles tendon and strengthens the swing phase.
• Plank (front and side): the core keeps your posture stable in the final kilometers or on long climbs.
• Rowing with barbell/dominoes: strengthens the back and shoulders.
• Bench press/flexion: provides strength in pectoral and arms, useful in braking and overall balance.

What is the core? 10 exercises to strengthen your muscles.

Four essential tips

• Warm up well: Never jump into a heavy squat without prior mobility and approach sets. The risk of injury increases.
• Control technique: Even if you're excited about lifting weights, form takes precedence over load. Poor deadlift posture can ruin weeks of race training.
• Listen to your body: If after a day of leg strength you notice discomfort or poor performance, adjust your next running session or delay quality training.
• Don't be afraid of "excessive" hypertrophy: The muscle bulk typical of runners who introduce strength will not turn you into a bodybuilder. It's about developing functional strength, not extreme hypertrophy. With proper nutrition, you will maintain your weight and lightness.

The experience of trainers and your own proof

Science supports the improvement of both recreational and professional runners in running economy and endurance through strength. One of the biggest mistakes they share is underestimating the power of the musculature in a repetitive impact sport. Most long-distance runners-especially those looking to progress to half marathons, marathons or ultras-face accumulated fatigue that takes its toll on technique and health. Strengthening your legs, lower back and core greatly reduces those obstacles.

My recommendation: give it a try. Introduce a couple of strength sessions a week for at least six to eight weeks, carefully planning the intensity so as not to crush your intense running days. Keep a running diary: how you sleep, whether you find it harder or harder to maintain certain paces, and whether your perception of fatigue on long runs improves. It is very likely that, after this period, you will notice a change in your stability, in the freshness of your strides and, consequently, in your times.

Strength training is no longer a distant option or an optional accessory for the runner. From my own experience, and supported by the knowledge of my most trusted coaches such as Enrique Díez and Antonio Bores, incorporating strength exercises intelligently into your weekly routine can help you run with more ease, minimize wear and tear and attack the hills or final sprints with better guarantees. Plan your loading days well, respect the phases of the season and prioritize technique over weight. You will see how, in the long run, your legs will thank you, your GPSsports watch will thank you and your motivation will only grow. Ready to make that leap in quality? Test, evaluate and get back to enjoying running with the knowledge that your muscles respond to every step. Courage!