If you walk into most gyms today, you’ll see a major contrast between the weights used by men and women.
Some women will curl 5 pound dumbbells for 25 reps in an effort to “tone” their arms, while some guys will bench a ton of weight for only a few reps in an effort to put on muscle and increase strength.
The idea is that high reps help you lose fat and make a muscle more “toned”. On the other hand, low reps can help you build muscle and increase strength.
Is it really this simple? High reps for fat loss and low reps for strength and muscle building?
In this article, you will learn why it’s a smart idea to use both low and high rep ranges in your workout regimen if you want to build muscle, lose fat, or simply improve overall physical fitness. You will also learn why you can build muscle, increase strength, or lose fat with just about any rep range, but some rep ranges are more optimal than others for each training outcome. Finally, in terms of time-efficiency, safety, and overall effectiveness, the ideal rep ranges to elicit the greatest changes in body composition (both fat loss and muscle building) likely occur within the 6-12 rep range.
The Strength Continuum is a framework where strength and endurance exist on a continuum that defines the relationship between weight, reps, and training outcome. Strength is represented by the 1 repetition maximum (1RM), which is the maximum weight that can be lifted for one rep, and endurance is the ability to exert a lower force repeatedly over time.
Low repetitions with heavy weight increases strength, whereas high repetitions with light weight increases endurance. According to the concept, as repetitions increase there is a gradual transition from strength to endurance.
Below is a commonly used graph of the strength continuum. The training outcome “Hypertrophy”, which means muscle-building is not an entirely accurate label as you’ll learn more about in a moment.
This framework also works in line with our understanding of muscle fiber types. High reps develop Type 1 muscle fibers (“slow twitch”) that are endurance based and slow to fatigue. Lower repetitions activate Type 2 muscle fibers (“fast twitch”), which have greater power but fatigue quickly.
For optimal strength increases, the research conclusively supports low reps with heavy weight vs. high reps with light weight, but high reps can still elicit gains in strength as well.1
For example, in one study, 23 cyclists were placed into high resistance/low repetition (LR), low resistance/high repetition (HR), or cycling-only groups for a 10-week program.2
There were substantial strength gains in all 4 resistance training exercises tested for both LR and HR groups, but the LR group had “significantly” greater strength gains than the HR group in the leg press exercise. Interestingly, muscle hypertrophy and overall endurance was relatively equal.
As this study and many others highlight, for optimal strength gains, lift relatively heavier weight for low reps. This is in line with how Powerlifters train for competitions to help increase neuromuscular adaptation, which is the efficiency of the brain to control the muscles. You can get stronger as a result of increase in muscle size OR increase in neuromuscular adaptation.
Some believe heavy weights are only good for building muscle, but what about fat loss? Can lifting heavier help you burn more fat, or does it turn you into the hulk?
One study from the University of Alabama in Birmingham showed that dieters who lifted heavy weights lost the same amount of weight as dieters who did just cardio, but all the weight lost by the weight lifters was fat while the cardio group lost muscle along with some fat.3. The common belief is that high reps magically get rid of fat. While high reps with light weight to fatigue can create a muscular response, it does not necessarily remove fat better than low reps with heavy weight.
While more studies are needed to compare the fat loss effects of high reps vs. low reps, substantial evidence is mounting that it’s not necessarily the amount of weight that is used, or the number of repetitions that helps burn the most fat, but the intensity of the workout. The goal is to create muscular failure with less rest between exercises, which can have powerful hormonal, metabolic, and calorie burn effects (See: afterburn effect). In addition, for fat loss, proper nutrition will have a MUCH greater impact on fat loss than the specific rep range, or even workout.
Similar to fat loss, the number of rep ranges that is optimal for muscle building is open to debate and the research is inconclusive. Most research points to reps under 15 reps as being better for muscle building, but other research shows muscle building can be equally effective with light weight and high reps.
For example, a recent study of resistance-trained young men found that light weight with high reps, performed until failure, was equally effective in stimulating muscle proteins as a heavy weight with low reps.4
There is a common misconception that lifting heavier weights automatically helps you build muscle. That’s not the case at all. In fact, how much you eat in combination with the overall volume and intensity of the workout and how it becomes more challenging over time will make the difference, not necessarily the weight/reps. If you eat relatively less calories than you burn, you can lift very, very heavy weight and most likely not gain an ounce of muscle mass. This especially applies to women who have 1/10 the amount of the muscle-building hormone testosterone as men. In a calorie deficit, increases in strength are likely due to neuromuscular adaptation and not increases in muscle mass.
So now we know just about any rep range can help you increase strength, build muscle, or lose fat, but what ranges should you use? What should be your focus? The following proposes what may be optimal rep ranges based on specific goals.5
Strength – Under 6 reps (80-100% of exercise volume)
Hypertrophy – 6-15 reps (0-20% of exercise volume)
Endurance – 15+ reps (0-10% of exercise volume)
The top strength athletes in the world spend the vast majority of their time lifting very heavy weight for low reps. While we know higher rep ranges can also create strength gains, lower reps are optimal.
Strength – Under 6 reps (0-15% of exercise volume)
Hypertrophy – 6-15 reps (70-85% of exercise volume)
Endurance – 15+ reps (15% of exercise volume)
As stated earlier, the intensity of the workout is more important than the specific rep ranges for fat loss, but the following is a smart approach that combines what I consider the “sweet spot” of the 6-15 reps, which can further be broken down into 6-10 and 10-15. For less advanced lifters and the general population, those ranges can be changed slightly to 8-12, and 12-15.
There a couple very compelling benefits of the 6-15 rep range. First, you are getting significant muscle stimulation with much less chance of injury than lifting very heavy weights for low reps (under 6 reps). Second, it takes less time to workout than using 15+ reps all the time, which does not offer much added benefit. If you are a beginner, I recommend against using under 12 reps. If you don’t want to push yourself with low reps, there isn’t any need to go below 6 reps, or even below 10 reps if you are older, or fear getting injured. Lifting in multiple rep ranges will help stimulate a maximum amount of muscle fibers to help burn fat and improve overall fitness.
So how do you implement high and low rep ranges in your workouts? There are few primary options (1) complete low and high reps in the same workout using different exercises, (2) start out with higher reps (say 15 reps) and go down in reps as you complete multiple sets for a given exercise, or (3) change up your workouts, so that some are geared towards strength vs. endurance.
Strength – Under 6 reps (30% of exercise volume)
Hypertrophy – 6-15 reps (60% of exercise volume)
Endurance – 15+ reps (10% of exercise volume)
As you learned before, while research shows it is possible to build muscle with lighter weights, the traditional method is to lift relatively heavier weights and increase those weights over time. Of course, genetics play an important factor as does the composition of muscle fibers from one muscle to the next and one individual to the next.
If you are looking to increase strength, build muscle, and increase fat loss all at the same time (which is not a great idea for reasons discussed here – Can You Lose Fat And Build Muscle At the Same Time?), stick with the ratios in the Optimal Fat Loss section.
I hope this article was enlightening to help dispel some of the common myths associated with lifting weights and has empowered you with useful information you can apply to your current exercise regimen.
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