The marker most often cited and supported is gait speed.

How fast we walk is one of the most important physical characteristics to track as we age. Gait speed is directly linked to mortality and is a marker of functional capacity and general health status.

It is the “functional vital sign.”

Why is gait speed so important? It is predictive of an individual’s functional dependence, frailty, mobility disability, cognitive decline, frequency of falls, institutionalization, hospitalization, and cardiovascular-related events. You can use this graphic to visualize which speeds are necessary for specific tasks and which as markers as increased risk for adverse events.

In short, walking speed should be closely monitored as we age.

This is well known among healthcare providers. I often use the Timed-Up and Go and six-minute walk tests in the clinic to assess gait. It was one of the first outcome measures I was taught in PT School.

What wasn’t taught, was the importance of maintaining hip flexor strength

Don’t ignore the hip flexors

If you want to maintain gait speed, what should you target?

You could practice walking fast, but if the body’s capacity for generating speed declines, the will to walk fast will only carry so far. A recent study suggests improving hip flexor strength may be the answer.

This study evaluated 433 community-dwelling older adults. Each participant underwent a battery of tests to determine physical function, which included handgrip strength, maximal isometric strength of hip flexion, hip extension, hip abduction, knee extension, and toe flexion, the 5-time chair–stand test, the one-legged stance, the timed ‘‘Up & Go’’ test, the 30-s stair test, and range of motion.

The participants completed a questionnaire 12 months prior to the physical tests and at the time of the tests to assess functional capacity. The changes in scores helped the researchers determine who would be allocated to the decline and non-decline groups respectively.

After analyzing all of the data, the researchers found hip flexor strength was the primary determinant in the progression of functional capacity decline. This falls in line with previous research that suggested quad strength is a primary predictor of mortality.

How to improve hip flexor strength

I mentioned quad strength as one of the primary hip flexors is one of the four quadriceps muscles, the rectus femoris. The muscle crosses the hip and knee joints, allowing it to act as a hip flexor and knee extensor.

Hip flexion is necessary to help propel our legs forward during gait and knee extension is necessary for one of the other primary functional tasks.

Squatting.

Without quad strength, we can’t sit down and stand up effectively (or independently). You may have already guessed one of the exercises I am going to recommend.

Squatting is often referred to as the king of exercise for a reason. It is as functional as it gets. It can be altered easily as well. Here are a few variations to try:

• mini-squat, full-depth squat, split squat, sumo squat, goblet squat, rear-foot elevated split squat

You can perform knee and hip flexion exercises that are similar to the squat as well, such as lunges, step-ups, and step-downs.

These are largely quadriceps and gluteus maximus building exercises as they involve knee and hip extension. But as I mentioned earlier, the primary quadriceps muscle — the rectus femoris — is a hip flexor as well.

Training hip flexion specifically would be beneficial, however. Here is a progression for training hip flexors:

• standing marches
• seated marches
• Sitting on the floor with knees extended, alternate lifting your legs in the air
• Same as before, except this time, raise your leg over a small object (such as a cone or small box)

This progression specifically targets your hip flexors. Build up the height of the object for strength, the speed of the movement for power, and the duration of the activity for endurance. All are vital components of health.

To build strength, the exercise must be challenging. You have to be fatigued. Strength is how much force we can develop and will be necessary to maintain the ability to stand up for a low seat or the floor as we age.

To build power — how quickly you can contract a muscle and move — you have to train at a high speed. Power is the primary marker for fall prevention. It is how quickly we can correct when we stumble.

Endurance allows us to keep going for long periods of time. It will be a primary marker for community ambulation and staving off the walker. Exercises with high repetition and short rest breaks build endurance.

Strength, power, and endurance should be emphasized for all people, regardless of age. Research shows elderly and very elderly (80+ years old) can build strength and muscle. I emphasize all three for all of my patients in the clinic.

“Never skip the leg day” is a popular meme and saying amongst gym enthusiasts. While people tend to refer to aesthetics and body proportions, the saying also applies to life-long mobility.

Leg day is the most important day for maintaining our health and wellbeing.