20d • tactical fitness
Ask Stew: Running Out of Gas on the Navy PST
Have you ever noticed that when you take a fitness test, your individual scores are much better than your combined scores when tested together? While this could be a conditioning issue, it is likely more of a low blood sugar issue. A new study examines the effects of carbohydrate ingestion on exercise metabolism and physical performance, and compares low-carb diets with higher-carb diets. Here is a related question where this research can help you:
Stew, I recently took a Navy PST. While I usually do well on the swim and calisthenics, the run at the end is much worse than my normal run (when fresh). I imagine this is a fueling problem, but what do you recommend? I typically don’t eat many carbs, as I have been on a Keto-type of diet for several months and have lost over 20 lbs. What do you think? Thanks, Victor.
While this study is written on athletes in competitions lasting 2-3 hours or more, the concept still holds true for high intensity fitness testing such as a fast 500m swim (8-9 min), max pushups (80-100), sit-ups 80-100, and pullups 20, then a 1.5 mile run in 9 minutes. These are the type of advanced scores you should strive for, given the jobs you are seeking (SEALs, SWCC, EOD/Diver, Rescue Swimmer, Special Ops Corpsman). To reach this level of fitness, it requires consistent training, consistency, and fuel in the form of a carbohydrate that agrees with your digestive system. I usually go with a banana and juice before the test and sip on juice between events of the 5-event Navy PST. I found that once I started doing this, my scores were close to (within 5%) fresh max efforts in the individual events. No longer was I dropping on the last half of the 1.5-mile run, 1-2 minutes from my normal run time.
Your job is to continue training consistently and with a specific focus on getting used to the test. Swim first. Always start your swim with a 500-yard warm-up. Because, on the day when you take the test for real, you can calm down your “pre-game jitters” and nerves by saying, “500yds swim – this is my warmup.” Then, swim your pace, swim your race. See the 50-50 swim workout to help with this type of conditioning.
Combine Running with Pushups, Situps, and Pullups
The land portion of the test can be prepared while you test your carbohydrate-sipping strategy during workouts that are similar to the test. Do push-ups, sit-ups, pull-ups, then run. These can be a combination of pyramid, super-set, or max rep set workouts in what I call the perfect PST training week. These will teach you how to run after an upper-body pump and how to transition from calisthenics to the run cycle using a proven strategy I call the PST transition. This will also help running feel more normal after you do the transition exercise after the last pull-up during the 10-minute break before you run.
Here is Why Fueling Matters and What This Study Shows
In simple terms, eating or drinking carbohydrates (like fruits and juice) while exercising helps you perform better. Originally, scientists thought this was mainly because carbs prevent your blood sugar from dropping too low and protect your brain. Later, people believed that running out of stored carbs in your muscles made you feel tired, but they often ignored the role of low blood sugar in exhaustion. Here are the benefits of adding carbs before and during sustained activity:
- stabilizes blood sugar
- protects brain function
- delays a central nervous system shutdown.
Think of this as more of a neurological need: when blood sugar drops, the brain senses risk and signals the body to reduce effort. We all have called this feeling of “bonking” after these workouts muscle failure, but it is the brain protecting the body. Feed the brain – fuel the body!
This research shows that when your blood sugar drops during exercise (called exercise-induced hypoglycemia or EIH), you’re more likely to have to stop, even if you still have some muscle and liver energy left (glycogen). Eating/drinking carbs during exercise keeps your blood sugar steady, helps your body manage energy better, and lets you keep going longer, even if your muscles run low on stored carbs. Surprisingly, athletes who eat mainly protein and fat, with fewer carbs, can still perform just as well, but the timing of carbohydrates before and during the fitness test is the key.
Overall, the main reason to eat carbs during exercise is to avoid low blood sugar, especially during long workouts or when your body isn't good at making new sugar. While you may think MORE + BETTER, that is not the case. Keeping carb grams at 15-30 per hour is a logical dose for longer events and max-effort fitness tests that typically last 45-60 minutes.
Find the carbs that work well for you during workouts, not during your tests. Too often, many people will add a wide variety of things they have never done before, from carbohydrate supplements to caffeinated pre-workout, for the first time on the day of the test. This usually results in digestive distress or worse, in the case of caffeine.
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Ask Stew: Running Out of Gas on the Navy PST
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Veteran - Stew Smith (former Navy SEAL) helps military, law enforcement, and firefighter candidates and recruits succeed with coaching and programs.
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