Why your hip flexors and inner thighs might be the secret to a faster stride

When runners want to get faster, the conversation almost always points toward the back of the body. We talk endlessly about building stronger glutes, more explosive hamstrings, and resilient calves. While those muscle groups are undoubtedly critical for structural balance and power delivery, recent biomechanical research suggests we might be missing half the equation.

A study in the Annals of Biomedical Engineering looked at how targeted strength increases impact maximum running speed. Using sophisticated computer simulation models, researchers tested what happens when you increase the strength of individual running muscles by 10%.

The results were clear: the highest increases in maximum running speed came from strengthening two often-overlooked areas: the hip flexors and the hip adductors (your inner thighs).

The key finding: A 10% increase in the strength of the iliopsoas (your primary deep hip flexor) and the adductor longus (located in the inner thigh) had a significantly greater impact on overall running velocity than a corresponding strength increase in the glutes or hamstrings.

Understanding the Mechanics: Step Frequency vs. Step Length

To understand why these specific muscles move the needle so much, we have to look at the two components that dictate your running speed: how often your feet hit the ground (step frequency) and how much ground you cover with each stride (step length).

The data revealed that different muscles contribute to these variables in very unique ways:

• The Turnover Specialists: Strengthening the iliopsoas and adductor longus accelerated speed primarily by increasing step frequency. They allow you to pull the trailing leg forward through the swing phase faster, shortening the time your foot spends waiting to cycle through.

• The Stride Extenders: Conversely, strengthening the soleus (the deep calf muscle) and the vasti (your quadriceps) increased step length, but actually caused a slight decrease in step frequency.

• The Balanced Contributors: Muscles like the adductor magnus and gluteus maximus provided a healthy, balanced increase in stride length without sacrificing your turnover.

Moving Past the Guesswork in the Gym

As a runner, this data is incredibly practical. It tells us that a well-rounded strength routine should not just focus on pushing into the ground; it needs to focus on how efficiently you recover the leg forward.

If your current strength program consists solely of squats, deadlifts, and traditional glute bridges, you are likely leaving free speed on the table. To improve your mechanics and running economy, we need to specifically challenge the hip flexors and inner thighs under load.

Here is how to target those areas, ranked from the most approachable entry-level movements to advanced variations:

• Level 1 (Beginner): Seated Straight-Leg Raises & Standing Banded Adductions. Best for isolating the muscles with zero equipment strain.

• Level 2 (Intermediate): Banded Hip Flexor Marches & Lateral Lunges. Best for mimicking the actual movement patterns of your running stride.

• Level 3 (Advanced): Weighted Foot Lifts & Copenhagen Side Planks. Best for building maximum strength under heavy load.

At Kinplus, we focus on building these specific capacities safely. Instead of adding general fatigue with random exercises, we target the exact muscular relationships your stride requires.

If you want to stop guessing in the gym and start targeting the exact structural areas your stride needs, let's look at how you move. You can book a free 15-minute Kinplus Clarity Call on our website, and we can map out a real strategy for your specific goals.