For optimal muscle building (hypertrophy), most sets will fall somewhere between five and 20 reps per set as long as they are performed close to failure. Failure is defined as the point where you can’t perform another additional rep with good technique.
Generally speaking, lower reps lead to greater strength, whereas higher reps encourage muscle growth. Below five reps will lead to good strength increases but very little muscle growth (and we see this in powerlifters and Olympic weightlifters who return to Bodyscan with new personal bests but little, if any, increase in muscle mass).
Above 20 reps, the muscle adapts and becomes better at endurance and contracting at low levels for long periods. Consider a marathon runner who is, in effect, doing thousands of reps – endurance athletes like these have very low muscle mass.
You may have heard of slow-twitch and fast-twitch muscle fibres. There may be some debate about whether there are just two types of fibre but it is accepted that slow-twitch fibres are built for endurance (the runner), while fast-twitch fibres are optimised for strength and power.
Slow-twitch endurance fibres are smaller than fast-twitch, which is why your training regime should focus on maximising stimulus on the bigger, fast-twitch type; slow-twitch fibres contribute less to muscle hypertrophy, which is why endurance athletes are skinny.
The ratio of fast-twitch to slow-twitch muscle fibres we each have varies based on our genetics and our usual activity but it is not set in stone. How you train (your weights and reps) will encourage the increase and development of one or the other type of muscle fibre. So a runner can become a boxer (and vice versa) by changing the way they train and increasing the number of slow- or fast-twitch fibres in their muscles.
The way the body responds to different weights and rep ranges is why doing 10 reps of 20kg will not have the same effect as 200 reps of 1kg.
As for where in the 5-20 rep range you should aim for, different muscle groups and individuals respond differently, so I advocate some variety. You may feel different muscles really “working” at different ranges and giving you the best ‘pump’. Also, generally speaking, big compound movements (like squat and deadlift) lend themselves to lower ranges, while isolation exercises that target small muscles (like lateral raises and bicep curls) respond better to higher reps.
Injury prevention is very important in a successful weight training regime and so performing all your exercises with lower reps (below 8) would increase your risk. We see that muscle mass is more adaptive and faster to strengthen than connective tissue (tendons and ligaments). Adding in some higher rep work (15-20 reps per set) will allow lower loads to be lifted, less stress on the connective tissue leading to a lower injury risk whilst still maintaining the benefits for muscle growth on the muscle.
Muscle growth is an adaptive response and therefore in my opinion, it makes sense to have a variety of rep targets within the 5-20 rep range across the week of training. Just doing 10 reps for every set is likely to yield less of an adaptive response from the body as the body is receiving the same stimulus and it is the adaptation which causes muscles to grow.
In summary, keeping all sets between 5-20 reps and varying the rep target across your weekly training regime will see you yielding good results.
However, with all the above said, what matters more is the quality of your exercise. If your form is bad (and you are using momentum or gravity to move the weight, or not working the muscles the exercise was designed to stimulate) then you are wasting your time and the rep range becomes irrelevant!
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OK, mister, but where are you for the other 167 hours a week?
Many people can't understand why they aren’t losing body fat even though they’re eating less than they burn. The simple, inescapable, unassailable fact is this: if you are not losing weight you are not in a calorie deficit!
That means you're either eating more or doing less than you think - or both. Here are two common ways to go wrong.
1. You think you’re more active than you actually are
Time and time again, Bodyscan clients will describe themselves as "pretty active" or select "moderately active" on the Bodyscan calculator. In truth, most of us are overwhelmingly sedentary.
Look at it this way - there are 168 hours in a week, so doing three one-hour workouts or exercise classes amounts to just 1.8% of your week. If for the rest of the time you don't walk, run or cycle to work, you sit at a desk, watch TV, eat and sleep, you are little more than "sedentary".
Easy to forget. And hard to remember. Weekends count, unfortunately.
2. Forgetting weekends
Many people religiously track their calories during the week but then blow everything at the weekend with high-calorie takeaways, alcohol and meals out.
If your daily calorie intake for your diet should be 1500 (and let's say that's a deficit of 500 calories from a maintenance of 2000 calories per day) you should lose about 1lb of fat each week.
But if you eat 3250 calories on each day of the weekend (a blowout of 1750) your average daily calories over the week are 2000 (ie, maintenance). That completely wipes out any deficit and means you won't lose any weight at all.
If you think the 1750-calorie blowout seems far-fetched, it's less than one Sainsbury's 500g pizza, two pints of bitter and 150g of vanilla ice cream!
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