A common question we get asked is how many reps is best when you’re resistance training. Unfortunately there isn’t a black and white answer. It truly depends on what your training goal is. There are three main goals people have when resistance training: muscle strength, hypertrophy (muscle size) or muscle endurance. For each of these different goals, the amount of exercises, repetitions and weights used should change.
Endurance:
Muscular endurance refers to the number of repetitions of a single exercise you can do without needing to stop and rest. Examples include how many times you can do a full squat, a sit-up, or a bicep curl with a light-to-moderate weight before breaking form.
The specific type of muscular endurance used during cardiovascular fitness activities such as running, swimming, or cycling is usually called cardiovascular endurance or cardiorespiratory endurance and is different from the strength training definition. Endurance training for these types of physical activities builds the energy systems of the body, the muscle fibers, and capillaries that can sustain long periods of exercise, such as running a marathon or cycling a 100-miler.
The American College of Sports Medicine recommends using a program of lower intensity strength training to improve muscular endurance. The weight load should be less than 50 percent of the repetition maximum (the maximum weight you could use for one repetition of the exercise). This is a light to moderate intensity load. You perform a relatively high number of repetitions, 15 to 25 per set, for one or two sets.
To improve endurance for cardiorespiratory fitness activities such as running and cycling, progressively increase the time you spend in the activity at a moderate pace. While this will result in muscles that are geared for endurance, it is usually discussed as cardiovascular endurance.
Muscle endurance training must be related to your target activity, whether it's doing barbell squats or running a marathon. You likely have limited time for training each week, and you have to consider whether you spend it doing specific muscle endurance training or practicing your sport.
Hypertrophy
Increasing muscle size, also referred to as hypertrophy, is arguably the goal of most newbie lifters. But many lifters go about this type of training all wrong. Hypertrophy training calls for fatiguing muscle fibers to increase their cross-sectional area, which, after proper rest and recovery, causes the muscle to grow larger. A rest period of 30-90 seconds is recommended to prevent the muscles from fully recovering between sets. This recruits more muscle fibers to become stimulated.
Other factors influencing hypertrophy include a rep range of around 6-12, which results in a longer time under tension (around 30-45 seconds), a more moderate tempo for each rep, and a higher volume of sets.
Progression can either be achieved through a higher exercise density (more volume of training in the same amount of time or the same volume of training in less time), increased reps with the same loads, or higher loads with the same number of reps.
What does this mean in layman’s terms? If you are training for the sheer purpose to build muscle and reshape your physique, then you need to fatigue the muscle with moderate reps, plenty of volume, and short rest periods. Your focus should be the muscle working (muscle-centric) versus the load lifted (weight-centric).
So a typical week might look like a full body Monday, Wednesday, Friday, or a lower body day, upper body day, rest day, lower body, upper body across 5 days. But the most important thing is to find what works for you. Get professional advice if it’s overwhelming and don’t be scared to try new training splits.
The critical bit though is to leave at least 48 hours between hitting the same muscle group again. What you wouldn’t want to do is hit back two days in a row. That’s because our muscles actually grow when we’re at rest. Post training the muscles repair, and they grow back stronger and bigger – so if you hit the same muscle without adequate rest you’ll actually impede its growth.
Strength:
Pure strength is a different animal. Also referred to as low-speed strength, the goal here is to lift maximal or submaximal loads from point A to point B. Moving weight at a moderate speed is recommended, since the goal is to develop a high level of overall body strength with heavy loads. Power, on the other hand, relies almost exclusively on speed of the lift – which we will get into later.
Pure strength athletes, or those in need of more strength for their sport, are interested in performance, period. Powerlifters or anyone interested in raw strength gains typically have little interest in aesthetics. Methods for increasing strength overlap somewhat with hypertrophy training, specifically regarding progression, but the goal here is purely performance based.
Strength enthusiasts will commonly refer to percentages of max efforts or percentages of reps max (%RM). This is the maximum amount of weight lifted for a specified number of reps (XRM – X being the number of reps). Once that number is identified, a percentage of that maximum amount of weight lifted is used for training purposes. For example, if a lifter has a one-rep max bench press of 400lbs and wants to train with 90% of his max weight, he will train with a load of 360lbs (.90 x 400).
If your goal is strength-centric, then you will train in the 2-6 reps range with loads of 85% or higher of your 1RM, and relatively longer rest periods of 2-5 minutes. When lifting heavy, you will want to give your muscles plenty of time to recuperate to lift maximally for the next set.
Focus on the big compound moves (moves that involve multiple muscle groups) for strength and power – like the squat, deadlift, bench press and barbell row. Plenty of power lifters will focus just on those moves (adding the more advanced clean and press) focusing on low rep sets with big weights to increase strength. Of course, with proper nutrition, that’s also going to increase size. As you get stronger your muscles will get bigger.
References:
Randall F. D’Souza, James F. Markworth, Kirsten M. M. Aasen, Nina Zeng, David Cameron-Smith, Cameron J. Mitchell and Severine Lamon, Acute resistance exercise modulates microRNA expression profiles: Combined tissue and circulatory targeted analyses, PLOS ONE, 12, 7, (e0181594), (2017).
Ivey FM, Roth SM, Ferrell RE, Tracy BL, Lemmer JT, Hurlbut DE, Martel GF, Siegel EL, Fozard JL, Metter EJ, Fleg JL, Hurley BF. Effects of Age, Gender, and Myostatin Genotype on the Hypertrophic Response to Heavy Resistance Strength Training. The Journals of Gerontology. 55(11):M641-M648. November 2000.
Pescatello, Linda S. ACSM's Guidelines for Exercise Testing and Prescription. 9th ed. Philadelphia: Wolters Kluwer/Lippincott Williams & Wilkins Health, 2014. Print.