Fatigue has both good and bad connotations for exercise. On the one hand, you want to fatigue your muscles when you strength train to maximize growth and strength gains. Yet fatigue can also affect your performance when you work out in a way that’s negative and counterproductive. But what you might not realize is that fatigue comes in various “flavors.” Let’s take a closer look at types of exercise fatigue.
Short-Term Intense Exercise Fatigue
This type of fatigue is triggered by high-intensity exercise that places substantial stress on the axial skeleton. A few key things happen when you sprint, lift heavy weights, or do anything super intense. First, your muscles start churning through glucose without enough oxygen. That causes lactic acid to build up, which makes your muscles burn and leads to fatigue. Second, your body taps into its short-term energy reserves, like ATP and phosphocreatine. But those can run out if you’re really pushing it, leaving your muscles under-fueled.
And don’t forget about sweating! When you sweat buckets, you lose electrolytes like sodium and potassium. That throws off the signals to your muscles, so they don’t contract as well. So, what do you do? Build up the intensity of your workouts slowly so your body adapts. Fuel up with carbs so you have enough glucose. Stay hydrated and replace the electrolytes you lose during intense training sessions. And take little breaks to clear the lactic acid, as is a practice with high-intensity interval training.
The key is to be prepared, listen to your body, and support it with training, fueling, and smart recovery. Do that and you’ll bounce back from intense training sessions faster.
Prolonged Submaximal Exercise Fatigue
Extended periods of moderate-intensity exercise lead to this variant of fatigue. Ever notice how you start dragging when you go on a long run or ride your bike for hours? There’s a whole cascade of things happening in your body that team up to zap your energy.
First, your muscle and liver glycogen tanks start inching closer to empty. Once those reserves burn low, so does your blood sugar, and suddenly your legs feel like lead. But there’s more! Sweating for such a long time also drains you of fluids and key electrolytes like sodium and potassium. Getting dehydrated and lacking those minerals derails your muscle function.
So, hitting the wall during long efforts is a tag-team effort between declining fuel, dehydration, and mineral loss. Your best bet is to anticipate it by carb-loading, hydrating properly, and replacing salts along the way. That’ll keep the fatigue monster at bay!
Central Fatigue
Central fatigue is fatigue that originates in your central nervous system, as opposed to peripheral fatigue that comes from your muscles. Here are the reasons you develop central fatigue:
Neurotransmitters. These are chemical messengers that allow your brain to transmit signals from nerve cells to muscle cells at the neuromuscular junction. With sustained activity, you start to run low on critical neurotransmitters like acetylcholine. If those levels drop far enough, it gets harder for the signal telling our muscles to contract to get through.
Changes within the motor neurons. These are the cells responsible for directly telling our muscles what to do. Prolonged electrical signaling back and forth can cause metabolite buildup within motor neurons that makes them less excitable and less likely to keep firing at their initial rate.
Central drive from the brain. Even before local changes happen, descending signals from brain areas like the motor cortex start to fatigue from the effort involved in sustaining muscle contraction. If the brain eases up on sending those impulses down to the motor neurons, you can’t contract your muscles as efficiently.
Peripheral Fatigue
When our muscles get tired during exercise, it’s often because of changes happening in or around the connection between nerves and muscle fibers. A few key factors behind localized muscle fatigue include:
- Using up the ready energy supplies in our muscles and blood, like glycogen and glucose. Without enough fuel, our muscles struggle.
- Waste products like lactate and protons build up, which can interfere with muscle fibers’ ability to contract properly.
- Internal calcium handling becomes impaired, meaning less calcium gets released to trigger muscle contractions. So, we lose strength.
- Disruption of muscle membranes in ways that make it harder for nerves to activate the muscle effectively. Signals have a harder time getting through.
Mental Fatigue
Fatigue during exercise goes beyond just the physical changes in our muscles. Mental fatigue also plays a crucial role by making us feel subjectively tired and drained, even if our muscles still have capacity. This mental exhaustion and drop in motivation make it tougher to push through the physical challenges of working out. So, psychology influences fatigue too – it’s not just what’s happening in the muscles. Both physical and mental tiredness contribute to that feeling of being “spent” when we exercise.
So, what can you do to reduce exercise fatigue and keep it from interfering with your workout?
Rest and Recovery
Getting enough rest and recovery time between workouts is important. Taking breaks allows your body and muscles to recharge, so you don’t just get more fatigued over time. Rest days help minimize that building-up of tiredness so that you can stay at peak performance for the session. Without adequate recovery periods, you end up digging yourself deeper into exhaustion. So be sure to schedule a few days for complete rest or light activity – it’s key for both physical health and performance!
Nutrition and Hydration
Eating right and drinking enough fluids helps fight fatigue. By getting enough nutrients from foods and staying hydrated, you keep your energy levels up. This helps prevent muscles from running out of fuel since you’ve given them the building blocks they need. So, a healthy, balanced diet and staying on top of hydration can go a long way against feeling tired. Stocking up on nutrient-dense meals and sipping water throughout the day is a good fatigue-fighting strategy.
Electrolyte Replenishment
Electrolytes like sodium and potassium play a key role in how well our muscles work. When you exercise, electrolyte levels can change both inside and around muscle cells. Replenishing essential minerals is key for keeping muscles happy. Getting enough sodium, potassium, and other electrolytes helps sustain peak muscle performance during our workouts. So, focus on electrolyte balance – through sports drinks, coconut water, or foods with these nutrients. Proper electrolyte intake helps offset depletion from heavy sweating and supports our muscles in functioning at their best.
Address Medical Conditions
Health problems affecting nerves, muscles, or general wellness can play into fatigue too. If you’re having a chronic lack of stamina during your workouts, see your doctor. Simply writing things off as “fatigue” doesn’t get to the bottom of what could be going on medically. Addressing those factors is key to feeling your best day-to-day.
Conclusion
Now you know why you become fatigued when you exercise and strategies you can use to fight it during exercise and recover more fully. Take advantage of them.
References:`
- “Everything You Need to Know About Exercise and Fatigue – ACE.” https://www.acefitness.org/certifiednewsarticle/2948/everything-you-need-to-know-about-exercise-and-fatigue/.
- “Muscle Fatigue: Causes, Symptoms, and Treatment – Healthline.” https://www.healthline.com/health/muscle-fatigue.
- “Fatigue Causes – Mayo Clinic.” 11 Feb. 2023, https://www.mayoclinic.org/symptoms/fatigue/basics/causes/sym-20050894.
- “Recovery of central and peripheral neuromuscular fatigue after exercise ….” 01 May. 2017, https://journals.physiology.org/doi/full/10.1152/japplphysiol.00775.2016.
- “Muscle fatigue: general understanding and treatment – PMC.” 06 Oct. 2017, https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5668469/.
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