Strength Training for Endurance Athletes With Type 1 Diabetes

/May 23, 2025

The Power of Strength Training for Endurance Athletes from a Physiology Perspective: Anaerobic vs Aerobic Effects on Blood Glucose (Sugar) Levels as a Type 1 (Diabetic)

The topic of strength training as an endurance runner/athlete whether it is “how much do I really need,” “why does it help my running, etc.” is not only close to my heart but vital for anyone looking to optimize their athletic performance and manage blood glucose levels—especially for those of us living with diabetes (bonus: who doesn’t love the ‘peace’ of the gym after a long day of work—sweat, passion, muscles ‘popping’, you get the point ;)).

As a Type 1 Diabetic (T1D), I’ve seen firsthand how different types of exercise can impact blood sugar, and I’m excited to share my insights with you (much of this article is referring to my ancient 2015 Master’s Thesis: Integrating Meal and Exercise into Personalized Glucoregulation Models: Metabolic Dynamics and Diabetic Athletes).

Understanding Blood Glucose Regulation

For those managing diabetes, keeping blood glucose levels stable is essential to prevent complications and maintain overall health, but for everyone, essential to regulating energy levels during exercise (cue: the dreaded “bonk” when blood glucose plummets). Blood glucose serves as a primary energy source, and our bodies rely on various mechanisms—chiefly insulin—to regulate these levels.

In my experience, particularly during my prep for the Olympic Marathon Trials, I’ve learned how crucial it is to understand how exercise affects blood sugar, in combination with other environmental stressors: adrenaline, weather, terrain, illness/injury, you name it. Different types of workouts can lead to varying outcomes in glucose metabolism, and knowing how to navigate these can make all the difference and prepare you for race day if you train both systems effectively.

The Impact of Strength Training

During a personal study, and backed by research (ping me for sources!), I compared a two-hour strength session to a two-hour steady run (we will discuss the difference of steady vs easy in a later article!). The results validated with data what I already predicted based on my own tracking and use of a continuous glucose monitor (CGM): strength training, characterized by short bursts of high-intensity effort, primarily utilizes stored glycogen as fuel in the immediate sense, but switches to fat burning and glycolysis post-workout for up to 3-4 hours! This type of exercise has been shown to significantly enhance insulin sensitivity, which is particularly beneficial for those of us with insulin-dependent diabetes, and train the body how to quickly utilize glucose for short bursts of energy, underpinned by triggering the slower fuel sources, aka utilizing fat/protein, for longer duration, e.g. marathons.

When I engage in strength training, I observe a notable improvement in my blood sugar control in the hours after, despite potential spikes in blood glucose during strength training. The muscles become more efficient at utilizing glucose, allowing for better management of blood sugar levels even in the absence of insulin. This adaptation is crucial for anyone with diabetes, as it aids in maintaining stable glucose levels throughout the day while training the mind and body on how to deal with potential high blood sugars during workouts that might trigger an adrenaline response—increase hydration, tiny boluses of insulin, walking/aerobic activity in between sets, meditation, you name it!

Increased muscle mass from strength training translates to a higher resting metabolic rate, which means more glucose and energy stores in general are utilized—even when at rest.

The Role of Aerobic Exercise

On the contrary, aerobic exercise, which includes activities like running, cycling, or swimming, is essential for improving cardiovascular health and enhancing endurance. Longer sub-max efforts promote the body’s ability to utilize both glycogen and fat stores for energy, which is especially beneficial during longer endurance efforts.

Through my experiences as an athlete, I’ve found that aerobic training can lead to significant reductions in fasting blood glucose levels and improved post-meal glucose responses. The mechanism behind this benefit is due to triggering ‘fat-burning,’ or lipolysis driven by liver response as the activity progresses, and actually converts fat into energy—hence, why we can see a rise in blood glucose without any fuel after about 1 hour into aerobic exercise (note, this does NOT mean you don’t have to fuel!). Other benefits also include enhanced insulin sensitivity (similar to anaerobic) and increased glucose uptake by muscles during and after exercise.

The Synergistic Effects of Strength + Endurance

So, what happens when you integrate strength training with aerobic workouts? The combination can yield a substantial return on investment (ROI) for your training. I firmly believe in the philosophy of “hard days hard, easy days easy,” a topic for a future article. By coupling challenging aerobic interval sessions with strength training on the same day, you not only maximize your training time but also enhance your metabolic flexibility and ability to use different types of fuel—key for race day.

In my own routine, pairing these two training modalities has led to improved performance and resilience in addition to improved blood glucose control. This approach allows me to utilize the benefits of both anaerobic and aerobic exercises, setting me up for success in both daily activities and competitive events. Plus, I mentally enjoy being able to switch my focus from pounding the pavement day in and day out with strength in between.

Sample Tuesday:

AM – head to the track, warmup, 4 x 30 seconds hard / 2 minutes easy to get the heart rate up, drills and strides, and then 6-8 x 800m repeats at half marathon pace following by 4 x 200 FAST.

Either right after the track (ideally), and of course a protein recovery shake, head to the gym for something along the lines of the following:

3-4 supersets (e.g. do all of A exercises then move to B…) including:
- A: 5 x Back Squats HEAVY with 3 second pause at the bottom, 3 x broad jump immediately after squats, plank with dumbbell pull through,
- B: 8 each of goblet reverse lunge into step up, 30 second isometric split squat hold each leg, dumbbell row in quadruped position x 8 each arm,
- C: 5 x toes to bar (core exercise), 10 x hamstring curls on the aerobics ball, 10 each of curtsy squat holding a light plate. Finish with 90/90 mobility and core!

Note, if you can’t do the strength session right after your interval or speed session due to work constraints, it is more than OK to fit this in after work, even if it has to be a home version.

Conclusion: Creating a Balanced Training Plan

In conclusion, understanding the distinct effects of strength and aerobic training on blood glucose levels, and timing, is crucial for anyone, especially athletes with diabetes, who can quantitatively observe this magic at work as a key part of their treatment plan.

As we continue to explore the interplay between different training modalities, I encourage you to embrace a well-rounded approach to your fitness routine. By integrating strength and aerobic training, you can optimize your performance and health. Stay tuned for future articles where I’ll delve deeper into my coaching philosophy and share more insights on fueling your body effectively. Until then, keep embracing the grind, training smart, and staying healthy!