Whether you are a student who wants to be fitter, a netballer who wants a faster more powerful throw, a sprinter who wants to win that race or a weightlifter who wants to lift heavier weights, you are trying to make your muscles work better.
There are three major factors that affect how well your muscles perform – strength, power and endurance.
Strength
Muscle strength is also a result of the combination of three factors:
- Physiological strength, which depends on factors such as muscle size, the cross-sectional area of the muscle and responses to training.
- Neurological strength, which looks at how weak or how strong the signal is that tells the muscle to contract.
- Mechanical strength, which refers to a muscle’s pulling force and the way those forces can be changed using bones and joints as levers.
When we talk about the strength or muscles, we are describing the maximum force a muscle can exert. Muscle strength is directly dependant upon the size of the cross-sectional area of muscle, so if after a period of training, you increase your muscle size by 50%, you will also increase the force the muscle can develop by 50%.
For every 1 square centimetre of cross sectional area, muscle fibres can exert a maximum force of approximately 30–40 newtons (the weight of a 3–4 kg mass).
Example: Emily can lift 21 kg (210 newtons force) using muscles that have a cross-sectional area of 6 cm2. Use this formula to work out how many newtons per square centimetre her muscles can pull with:
Emily’s friend Alisha has larger muscles that have a cross-sectional area of 8 cm2. Use this formula to work out what weight Alisha should be able to lift if her muscle tissue is similar to Emily’s:
Power
When muscles contract or stretch in moving a load they do work, and energy is transferred from one form to another. The power of muscles refers to how quickly the muscles can do this work and transfer the energy.
Example: A weightlifter lifts 100 kg up a distance of 1.5 m. 100 kg has a weight force of 1000 newtons. Use this formula to calculate the work done (energy transferred) by the weightlifter:
If the weightlifter lifts the 100 kg explosively and takes only 0.5 seconds to make the lift, use this formula to calculate the power their muscles produce:
Where does the energy come from and where does it go?
The energy for muscle contraction comes from glucose transported by the blood and deposited in muscle tissues. In the weightlifter example, the energy has been transformed to gravitational potential energy. Also, heat energy will be generated in the muscle tissues themselves. This means that the muscles will have transferred even more energy than the amount calculated above.
Putting the relationships together
There are three different equations that can be simplified to make an even more useful equation:
Because
the formula can be rewritten: power = force × velocity
Sports scientists use this formula to measure the power profiles of particular sets of muscles by measuring both the force of the muscles and the speed with which they are contracting or lengthening. They have found that the greatest power is produced when the load is much less than the maximum load on the muscles.
Endurance
Muscle endurance refers to how well the muscles can exert and hold maximum force over and over and over again.
Medically reviewed by Lauren Jarmusz, PT, DPT, OCS — Written by Beth Sissons on January 28, 2021
Muscular endurance refers to how long muscles can sustain exercise. Improving muscular endurance can help enhance overall health and fitness.
This article explores the benefits of muscular endurance, the best training routines to enhance it, and how people can adapt these techniques into common exercises.
We will also look at tips to prevent injury during training and how to design an exercise program that could lead to long-term performance and health benefits.
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Muscular endurance is the ability to continue contracting a muscle, or group of muscles, against resistance, such as weights or body weight, over a period of time.
Increasing the performance of these muscles means they can continue to contract and work against these forces.
Greater muscular endurance allows a person to complete more repetitions of an exercise, for example, pushups or squats.
According to the American Council on Exercise (ACE), the benefits of muscle endurance include:
- helping maintain good posture and stability for longer periods
- improving the aerobic capacity of muscles
- improving the ability to carry out daily functional activities, such as lifting heavy items
- increasing athletic performance in endurance-based sports
Muscular endurance tests measure how many repetitions of a movement people can do before the muscles reach a state of fatigue and cannot continue the exercise.
Many tests focus on measuring upper and lower body muscle endurance by measuring how many pushups, squats, or situps people can achieve.
A person can work with fitness instructors to measure muscular endurance or record how many repetitions of a particular exercise they can perform before reaching the fatigue state.
To increase muscular endurance, ACE recommend a combination of lower and upper body exercises, with strengthening exercises to target the whole body.
Moderate resistance training, with short intervals in between for rest, creates short bursts of tension to build strength.
Circuit or high-intensity interval training (HIIT) can be a suitable way to combine cardio and strength training into one workout.
Unless a person’s fitness goals involve training for a particular endurance-based sport, training for muscular endurance alone may not be the most appropriate strategy.
The best exercise programs mix strength and muscular endurance training.
Some evidence also suggests that exercise programs that people find enjoyable may be more likely to generate long-term benefits, as they may be more likely to stick with them.
A 2015 study comparing HIIT and steady-state training notes:
“Variety in the type of exercise is as important as the type of exercise. Particularly considering that the health benefits of exercise have to be viewed in the context of the likelihood that exercise is continued for several years, not just the weeks of a controlled study.”
When training to improve muscular endurance, what matters most is not the type of exercise, but how people design their workout.
People should take into consideration the following when tailoring a workout to boost muscular endurance:
- the number of reps
- the weight or resistant force on the muscles
- the number of sets
- length or rest periods
According to the National Strength and Conditioning Association, individuals training for muscular endurance should aim to complete three or more sets of 15 or more exercise reps with a load that is 50% or less of their one rep max (RM).
A person’s one rep max is the maximum load with which a person can complete one repetition of an exercise.
For example, a person may wish to use the leg press machine at the gym to build endurance in the legs.
If they have an RM of 300 pounds (lbs), they should aim to perform 2–4 sets of 15 or more reps with a load of 150lbs or less, with brief rest periods between sets.
As their muscular endurance for this exercise increases, they may wish to make the exercise more challenging by reducing rest times between sets, or increasing the reps per set, rather than increasing the load weight.
A person can apply the same principle of high rep and set volume, low–moderate load, and short rest periods to any exercise, such as bench presses, dumbbell curls, pushups, or squats.
People can choose exercises that suit their preferences and are challenging yet enjoyable enough to sustain training.
Example exercises
As we have already mentioned, there are no specific exercises that are better for training muscular endurance than others. The design of a training program makes it suitable for endurance training.
However, ACE recommend the following exercises for building muscle endurance, which a person can perform at home without equipment:
Pushup
A pushup works the triceps, chest, and shoulder muscles.
- Start in a pushup position by lifting the body off the ground with the hands and toes, with the body in a straight line, horizontal to the floor.
- Keep the hands flat on the floor shoulder-width apart and at roughly chest level.
- Start with the arms straight, then bend the arms while keeping the body straight and engaging the core and glutes, to lower the body until the chest is close to the ground.
- Straighten the arms to return to the starting position.
- Repeat for 5–15 times, depending on difficulty, to perform one set
A person can also work the tricep muscles more by placing their hands close together and turn them inward, so the fingers and thumbs form a diamond shape.
To make the exercise easier, a person can place their hands on a bench or other stable, raised surface.
People can also modify a push up by placing the knees on the floor to make it easier, or lift one leg off the floor to make it more difficult.
Squat
A squat works the glutes, calves, quads, and core muscles.
- Stand with the feet just over shoulder-width apart with the toes pointing slightly outwards.
- With the head facing forwards in a neutral position and back straight, extends the arms in front, so they are parallel with the ground.
- Squat down by bending the knees, keeping the body weight centered over the arches of the feet and the thighs parallel to the floor.
- Keep the back straight with the shoulders back and chest forwards.
- Use the feet, legs, and hips to push back up to the starting position.
- Beginners should aim for 5–10 reps, and they may perform the squat against a wall or end the movement in a seated position on a low surface to make it easier.
Abdominal crunch
An abdominal crunch works the abdominal muscles:
- Lie on the back with knees bent and feet flat on the floor.
- Place the hands lightly on the back of the head and chin tucked.
- Slowly curl the upper body towards the knees, keeping the lower back on the mat.
- Slowly lower back down to the starting position.
- Perform 10–15 repetitions for one beginner set.
Pike crunch
Another example of an abdominal crunch is the pike crunch:
- Lie with the back flat on the floor, with legs outstretched and arms above the head.
- Lift the torso and legs off the floor to form a pike position.
- Place the legs at right angles straight up in the air and reach with the arms toward the feet.
- Slowly lower the legs and torso back to the floor.
- Perform for 10–15 repetitions for one beginner set.
A person can also hold a stability ball between their ankles during this exercise.
Lunge
A lunge works the abs, buttocks, hips, and thighs:
- Stand up straight with the feet together.
- Bend one knee, lift the opposite leg, step forwards on to it, place the foot flat on the floor, and bend the supporting leg, so the knee reaches the bottom.
- Use the front leg to push back up to the start position and repeat for the opposite leg.
- Perform for 10–15 repetitions on each leg for one beginner set
Plank
A plank works the core and back muscles.
- Start by lifting the body off the ground with the hands and toes, with the body in a straight line, horizontal to the floor
- Keep the hands flat on the floor, with straight arms and wrists and the elbows directly underneath the shoulders.
- Keep the chin tucked in, with the abs and thighs tight.
- If the person is a beginner, hold for 30 seconds, rest for around 1 minute in between.
- Repeat the plank at least three times.
A person can modify this exercise by resting on the forearms instead of the palms if they find it challenging to hold the plank position with straight arms.
Tips to prevent injury during a workout include:
- warming up with dynamic stretches before exercising, for at least 5 minutes
- making sure to maintain proper posture and technique, and consulting with a fitness professional if unsure of these
- exhaling during movements requiring more effort and inhaling on easier parts of the exercise
- resting certain muscle groups at least 24 hours after working them out
- cooling down and stretching after exercise
- stopping physical activity if ill or injured
Muscular endurance is a muscle’s ability to continue contracting against resistance over a period of time.
People can improve their muscular endurance with strength and cardiovascular training.
Last medically reviewed on January 28, 2021
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