Zenith Within by Dr. Sara

Zenith Within by Dr. Sara

How to Strengthen Your Body’s Armor Against Time

Part 2 of 2: Cardio vs. Strength Exercise

Sara Redondo, MD's avatar
Sara Redondo, MD
Oct 08, 2025
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The engine was built last week. The roadmap was established for how cardiovascular exercise will add years to your life.

How to Train Your Heart for Decades of Extra Life—Starting Now

How to Train Your Heart for Decades of Extra Life—Starting Now

Sara Redondo, MD
·
Oct 1
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A strong engine is the essential starting point for longevity, but what does it matter if you have a 100 year engine but it’s parked inside a rusted out chassis?

This week, we build the chassis, the suspension, and the armor. Generally put, we are building strength.

If cardio is your investment in a longer lived remaining life, strength training is your investment into a richer healthy remaining life.

Strength is the physical currency that is available to you to spend, when asked, throughout your extra years of life, with vitality, independence, and enjoyment.

Strength training means many things depending on the audience. For many, it elicits images of professional bodybuilding or elite sport athletes, but that will not be the definition of the term here.

True strength is being able to lift your grandchild into the air, and have no thought about it. It is carrying all of your groceries in one trip. It is getting up off the floor with ease, and having the belief that your body will do as it’s expected to, no matter what it is you’re planning to do. It is your armor against the attacks of aging.

We’ll share key metrics today that define a strong and resilient body.


Your Healthspan Dashboard

Just like your cardio, there are a few instrument dials on your dashboard that tell the story about your physical resilience and quality of life.

1. Muscle Mass (Your Metabolic Bank Account)

Think of your muscle as a savings account for your health. The more muscle you have, the more “metabolic currency” you have.

Muscle is the primary location of blood sugar disposal in the body, so it is your primary protector against insulin resistance and type 2 diabetes1. When you become ill or injured, your body has the ability to pull usable amino acids from muscle to heal and recover.

A body that has more muscle is a body that will demonstrate more resilience.

2. Bone Density (Your Body’s Scaffolding)

As we get older, our scaffolding that we call bones can become flimsy.

Weak bones can lead to osteoporosis and fractures that can alter who you are as a human. Strength training is the absolute best signal you can send to a body to build and maintain strong dense bones.

It literally tells your skeleton, “We need to be strong, reinforce the structure”2. It is the maintenance that continues to happen that keeps your internal scaffolding from being flimsy.

3. Grip Strength (Your Body’s Vital Sign)

This may surprise you, but the simple act of how hard you can squeeze your hand is one of the most powerful predictors of future health, disability, and even cognitive decline3.

It serves as an excellent proxy for your overall body strength. A firm handshake is a sign of a body that is still robust and capable.

These metrics are the physical building blocks of an independent and vibrant life.

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The Proper Mindset

Before we pick anything up, let’s address two typical concerns.

1. “I Don’t Want to Get Bulky”

I admit I worried about this before I began strength training.

First, for nearly all adults (and most women especially), gaining large amounts of bulky muscle is extraordinarily difficult. It takes tremendous effort, specialized training and nutrition, with a bodybuilding-type regimen. That is not our goal.

We want to develop strong muscle, dense muscle, and functional muscle that improves our whole-body ability.

2. “Isn’t It Dangerous?”

Like any activity, inappropriately done it can be.

However, appropriately done—that is, starting with light weight, concentrating on technique and progressing slowly—the risks associated with strength training are incredibly low and actually an excellent modality to combat injuries from weakness.

You were made to push, pull, and lift things off the ground. We are simply waking up what your body was designed to do.


The 5-Minute Go-To Warm-Up

Do this straightforward routine to get your body ready for movement before every workout (both cardio and strength).

  • 1 Minute of Marching or Light Jogging: To raise your heart rate.

  • 10-12 Leg Swings (Forward & Back): On each leg.

  • 10-12 Leg Swings (Side-to-Side): On each leg.

  • 10-12 Arm Circles (Forward & Backward): On each arm.

  • 10 Torso Twists: To mobilize your spine.

  • 5-8 Bodyweight “Air” Squats: To warm up your hips and knees.

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Navigating Common Challenges: Your Questions Addressed

1. “I Missed A Workout, Or A Whole Week.”

Life is busy, I know. And it’s more important to not try to “make up” for it by doing two workouts in one day.

Get back to the schedule exactly where you left off the week before. The goal for you is consistency versus perfection.

2. “Some Days I’m Just Not Motivated. What Should I Do?”

Motivation comes and goes, but habits get you through the times without motivation.

On low motivator days, make a deal with yourself: just do your 5-minute warmup.

More often than not, you will feel ready to continue on. And if not, you still do better than nothing with a 5-minute warmup.

3. “What About My Bad Knees/Sore Back?”

You should listen to your body above all other competing interests.

If something hurts sharply, then stop. If it aches chronically, consider moderate exercises related to low-impact cardio (cycles or swimming) or consider the strength exercises that aren’t impacting that area.

For squats let your form be impeccable and only squat as low as is comfortable for you. And by all means, always consult with a physical therapist, when in doubt.


The Longevity Exercise Blueprint

In today’s post, you’ll discover:

  • A simple, do-anywhere strength plan built around the five movements you use every day—so real life feels lighter.

  • An easy “effort gauge” to pick the right weight without math (good form, no ego, steady progress).

  • Two plug-and-play full-body routines: one for home with minimal gear, one for the gym—both written for busy adults.

  • A clear, age-smart protein guide so your training actually turns into strength (no calorie spreadsheets).

  • Weekly layouts to balance cardio and lifting space—so you can build endurance and muscle without fatigue.

  • An easy to hang a printable checklist + tracker that will keep you consistent, and measure your victories, while you always know what you are supposed to do during a given session.

Upgrade to get the full blueprint, routines, and printables.

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