Muscles won’t become stronger or grow in size unless you force them to. Without placing a stimulus on them, there’s no need for them to grow or become capable of generating more force. However, strength training, by asking your muscles to work harder than they’re accustomed to, can lead to significant muscle growth and strength gains. That’s the purpose of resistance training!
What determines the results you get from resistance training? The gains you get depend somewhat on age, gender, and diet, but how you train is a factor too and that’s the part you have control over. Improper training or lack of consistency can stymy strength and hypertrophy gains, but at the other end of the spectrum, overtraining, without giving your muscles adequate recovery, can too.
When you’re planning your training, three important variables that affect strength and hypertrophy training gains are intensity, volume, and frequency. Let’s look at the role that each plays and how you measure each one.
Intensity is the amount of resistance you use when you train – how heavy the weights are you’re lifting. You should determine the resistance based on your goals, whether you’re trying to build strength or muscle size, and limitations such as recent injuries. For example, if you’re recovering from an injury, lighten up on the weights and do a higher number of repetitions until you’ve healed.
In the absence of injury or other limitations, intensity depends on your goals. If your main goal is strength gains, the ideal formula is to work with a heavy resistance that allows you to do 2 to 5 repetitions before your muscles fatigue. This usually corresponds to lifting at 80 to 90% of your one-rep max.
If you’re trying to build muscle size, a moderate resistance (around 60 to 80% of one-rep max) where you can do 8 to 10 reps before your muscles fatigue is optimal for hypertrophy since you need a higher volume to hypertrophy muscles as opposed to building strength. For general conditioning and to build muscle endurance, use lighter weights and higher repetitions.
When you use a heavy weight, you apply mechanical stress to your muscles while adding more volume increases metabolic stress. Mechanical stress is most important for strength gains, but mechanical and metabolic stress are helpful for hypertrophy gains.
Volume is the amount of work that you do per exercise (per set) multiplied by the number of exercises. For example, if you’re doing a strength exercise, your total volume is the number of sets multiplied by the number of reps in each set. If you do 3 sets of squats and 10 repetitions during each set, your total volume is 30 repetitions. You can also think of volume as the total work your muscles do in a given period (e.g., 1 week).
Another way to measure volume is to consider the total volume load. To get this value, multiply the total number of sets by total repetitions by the total amount of weight you used.
Volume plays a key role in muscle hypertrophy gains. for example, a study found that increasing the weekly training volume for a muscle group increases muscle hypertrophy linearly; greater volume leads to greater muscle hypertrophy.
However, some research shows that the only sets that count for the linear increase in muscle growth are those that lead to muscle failure. In other words, increasing training volume without training to failure won’t necessarily lead in a linear manner to greater hypertrophy gains.
One study found that that hypertrophy gains were greater with increasing volume up to around 7 sets in one training session, based on using long rests of 2 or more minutes between sets. Additional sets in a single session didn’t boost hypertrophy gains further. But for some people, especially beginners, 7 sets is too fatiguing and is something they should work up to. What works for one person isn’t always ideal for another. Plus, even a conditioned person shouldn’t use high-volume training every time they train.
Frequency is the number of training sessions you do for a given muscle group within a period, usually a week. For example, if you perform each set of exercises in your workout 3 times per week, this is your frequency.
An increase in training frequency can lead to greater hypertrophy gains because it boosts total training volume, but increasing frequency beyond a certain point, more than 3 or 4 times per week, may reduce hypertrophy gains because your muscles don’t have enough time between sessions to fully recover.
How much recovery time you need between training sessions depends on the volume of your training and how quickly your muscles recover from damage. You need more time to recuperate from a higher volume training session than one where you do a lower volume. Plus, there are probably genetic differences in how quickly people recover after a training session.
Most of the evidence suggests that training 2 or 3 times per week leads to greater hypertrophy gains than training only once per week. However, it’s not clear that 3 sessions per week is superior to 2. It’s not clear whether more frequent training increases strength gains more than training only 1 or 2 times per week.
Don’t Forget about Progressive Overload
To continue to gain strength or muscle size, you must increase the challenge on your muscles, as your muscles adapt to the stimulus you place on them. Progressive overload is fundamental to maintaining strength and hypertrophy gains. The easiest way to use progressive overload is to increase the resistance but you can also boost training volume to boost.
Intensity, volume, and frequency are the three main variables that determine hypertrophy and strength gains, but you can also alter the stimulus on your muscles by changing the tempo of your reps, changing exercises, the exercise order, rest between sets, and range-of-motion of the exercise.
The Bottom Line
Now you know a bit more about three major factors that affect strength and muscle hypertrophy gains and how to measure them. However, it’s most important to find what works for you.
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