When you consider powering your body, what do you think about first? While food may be a good answer, many do not consider muscle mass and endurance a huge factor in athletic performance and physical and metabolic health.
Muscular endurance is the ability of a muscle group to remain active and perform repetitive actions against a particular force over a period of time. The more muscle endurance a person has, the greater is their ability to complete more reps of a specific exercise such as sit-ups, lunges, squats and pushups. (1)
The American Council on Exercise lists several key benefits of muscle endurance, such as maintaining proper posture, improving our daily function by allowing us to lift heavy items and by increasing our overall athletic performance. (2) In addition, muscular endurance exercise can help with maintaining heart health, facilitating weight loss, boosting mood and the quality of sleep, aiding longevity and reducing age-related decline. (3)
Muscle Workouts
There are three main ways to work out muscles, namely strength training, cardio and non-exercise physical activity.
1. Strength training
Strength training is when a person moves their body against a certain amount of resistance. Some examples are resistance machines and bands, free weights or simply bodyweight. (9) There is a difference between muscular strength and muscular endurance. Namely, the strength of our muscles decides how much weight we can lift. To build more muscle strength, a person would focus on lifting heavy amounts of weight with fewer repetitions. On the other hand, muscular endurance is determined by how many repetitive movements a person can do before they exhaust themselves. Therefore, to build more muscular endurance, a person would focus on bodyweight exercises, running, swimming, etc. (10)
To improve muscular endurance through strength training, a person should focus on doing a high number of repetitions using light weights. For example, a person could use a weight that is less than half the maximum weight they can lift and then perform two, ten sets of lunges, squats, bicep curls, etc. (12)
Partaking in strength training helps ensure that our bones, muscles and connective tissue increase their metabolic rate.
2.Cardio
Cardio exercises require large amounts of energy and increase one’s heart rate and oxygen intake while working large muscle groups. (13) In addition, cardio exercises can help manage high cholesterol, high blood pressure and obesity. (14)
Here are several examples of cardio exercises that can build muscular endurance when done consistently:
- Running
- Jogging
- Walking
- Swimming
- Dancing
- Biking
The American Heart Association recommends 150 minutes per week of exercise that produces an elevated heart rate. An elevated heart rate is defined by a target heart rate based on age. (15)
A person can build their muscular endurance by partaking in any cardiovascular exercise for a minimum of twenty minutes per day, three times a week. Remember, it is essential to warm up and cool down before and after exercise to avoid injury. (14)
3.Non-exercise physical activity
Non-exercise physical activity or non-exercise activity thermogenesis (NEAT) refers to everything outside of the exercises defined above. This activity typically refers to daily housework, taking the stairs or a leisurely walk. This non-exercise physical workout will closely depend on the individual’s current physical conditioning. For example, a young, strong person walking to the end of their driveway to get the mail would likely be defined as non-exercise physical activity. Although non-exercise physical activity will not increase muscular endurance at the same rate as strength training and cardiovascular exercise, it is a simple, achievable way to build endurance and burn more calories throughout the day. (16)
How does glucose absorption in muscles differ with workout intensity?
Exercise causes local vascular dilation due to the build-up of carbon dioxide (CO₂) and lactic acid. Both these waste products stimulate the surrounding blood vessels and tissues, which allows more blood flow to the area.
Glucose uptake in a skeletal muscle increases with exercise intensity. This is due to the fact that more CO₂ and lactic acid are formed, thus stimulating more local blood flow and glucose uptake. It is interesting to note that insulin is the key to allowing glucose to enter into the muscle cells for utilisation and glycolysis. Insulin resistance occurs when cells in your muscles don’t respond effectively to insulin and can’t easily absorb glucose from your blood.
A study observed an increase in myocardial (heart muscle) glucose utilisation during mild (30% intensity) and moderate (up to 55% intensity) workouts but decreased when the intensity was raised to 75%. This was in contrast to skeletal muscles, in which glucose uptake increases linearly with an increase in the intensity of the workout. (17)
It is suspected that the lactic acid itself starts to be utilised as a source of fuel during high-intensity exercise. This suggests that during high-intensity exercise, substrates other than glucose are used for increased myocardial energy.
Stable blood glucose levels for maximising muscular endurance
Simple ways to maintain blood glucose levels for maximising muscular endurance are to fuel with small quantities of carbohydrates frequently, consume protein-rich foods post-workout, reduce coffee intake and make sure to consume carbohydrates in between workout days. (18)
Now, let’s break down the science. The liver is largely the central hub for the metabolism of fats, amino acids and sugars. The pancreas is a secondary organ that helps to digest and utilise these same macronutrients.
In the liver, there are two major pathways that complement each other and are utilised at different times: glycolysis and gluconeogenesis. The liver uses these two metabolic pathways to stabilise and maintain an appropriate blood glucose level. Let’s review the ways in which our body maintains a stable blood glucose level and how this knowledge can help us get the most out of our workouts.
1.Food absorption
The body through the food we eat. Complex sugars and carbohydrates are broken down by amylase enzymes, which cleave certain chemical links that bind the simple sugars (i.e. glucose) into complex chains called carbohydrates. Once the carbohydrates are broken down into simple sugars the body utilises the glucose directly in the cells for metabolism.
2.Stored glucose
Our bodies store glucose in the form of glycogen in the liver, which can store up to 16 hours (typically storing 8–12 hours) worth of glucose in the glycogen form for use when not actively eating.
This glycogen is valuable for maintaining blood glucose levels while fasting. Breaking down glycogen into glucose is a very fast process that occurs between meals.
This is where the term ‘carbo-loading’ comes into play. An individual looking to have a steady supply of glucose will eat carbohydrate-rich foods prior to a significant workout to have plenty of glucose that is easy to access.
Carbo-loading can restock diminished glycogen reserves. In fact, the most decisive factor in recovery time is the rate of glycogen repletion. This is why it can be extremely beneficial to consciously consume carbs when we are getting ready for or recuperating from high-intensity exercise.
The idea is to fill up our liver and muscle glycogen stores. As our carb intake increases, our average glucose will trend upwards. This helps to increase the supply of glucose and glycogen in our system to better prepare for these workouts.
When we carb load ≤ 60 minutes before an intense workout, insulin and blood glucose levels are reported to be elevated immediately, and they may even negatively impact our performance later. Our last food intake should be ideally timed before the hours that define our specific training. The amount we eat and what we eat will also affect the timing of your workout.
A study suggests that consuming 30 grams of protein soon after a bout of endurance exercise (one where bench presses and squats were not involved) aids muscle protein synthesis. (20) It’s important to have a well-rounded diet that does not ignore macro and micronutrient food groups.
3.Stored fats and lipids
Suppose the body runs out of stored glycogen in the liver for a glucose source and does not have a source of carbohydrates supplied by food. In that case, the liver will use the metabolic pathway of gluconeogenesis to break down lipids and fats (stored in the adipose tissue) and ultimately produce new glucose molecules that it can supply to the bloodstream. Outside of glucose utilisation, the body systems can use ketones and other energy sources if glucose is too scarce, but that discussion is for another time.
When our aim is to hit peak performance during moderate- or high-intensity training exercises, it is extremely important to provide ample glucose to our muscles. This will help with metabolic efficiency and give us enough fuel for our working muscles.
It’s ideal to make sure that our glucose levels do not drop too rapidly, leading to glucose unavailability. As our glucose supply drops, our abilities like balance and stability might get impaired.
Studies show that episodes of hypoglycemia can lead to cognitive decline, difficulty in focus, mental weakness, impaired judgement and a lack of precision and accuracy in complex motor tasks. (19) This can not only impede your performance but also be dangerous, so make sure that you keep your glucose levels in check.
Conclusion
Muscular endurance is the ability of a muscle group to remain active and perform repetitive actions against a particular force over a period of time. There are several main ways in which we can work our muscles, like strength training, cardio and non-exercise physical activity.
In a skeletal muscle, the more intense the workout, the higher glucose uptake. This is because more waste products are being formed, thus stimulating more local blood flow and glucose uptake. However, glucose uptake in cardiac muscles increases during low- and moderate-intensity workouts but drops during high-intensity exercises.
We can replenish our glucose levels while we are training. When our aim is to hit peak performance during moderate- or high-intensity training exercises, it is extremely important to provide ample glucose to our muscles. Simple ways to maintain blood glucose levels for maximising muscular endurance are consuming small amounts of carbohydrates early and frequently, eating protein-rich foods after workouts, reducing coffee intake, and consuming carbohydrates in between workout days. This will help with metabolic efficiency and give us enough fuel for our working muscles.
Disclaimer:The contents of this article are for general information and educational purposes only. It neither provides any medical advice nor intends to substitute professional medical opinion on the treatment, diagnosis, prevention or alleviation of any disease, disorder or disability. Always consult with your doctor or qualified healthcare professional about your health condition and/or concerns and before undertaking a new health care regimen including making any dietary or lifestyle changes.
References
- https://www.medicalnewstoday.com/articles/muscular-endurance#what-it-is
- https://www.acefitness.org/education-and-resources/professional/expert-articles/5495/7-different-types-of-strength-and-their-benefits/
- https://www.livestrong.com/article/513988-five-benefits-of-muscle-endurance-activity-exercise/
- https://ultrahuman.com/blog/metabolism-how-to-measure-8-ways-to-improve-it-affects-the-body/
