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Paige Waehner

Fit Question - Why does my trainer tell me to do 8-12 reps? Isn't more better?

By February 15, 2013

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When I first started lifting weights, I didn't really know what I was doing or why. My sister, a personal trainer, told me what to do, what weight to use and how many reps to do. I never questioned her instructions, mostly because she might beat me up if I did, but once I got into the fitness industry I got curious about all those little rules we follow; 3 sets of this or 12 reps of that. Where did these numbers come from?

I have a few readers who are in the same boat. They started lifting weights, following the general guidelines, but suddenly wondered - why 8-12 reps? Why not 20 or 30? I've gotten this question a few times and thought I would cover some of the basics for those of you who are curious about it.

The rep ranges we use are actually based on percentages of one rep maximum (the amount of weight you could lift one time). What experts have learned is that when we lift weights at above 85% of our one rep maximum, which comes out to about 6 reps per set, the risk of injury increases dramatically. When we train at 65% of our one rep max, about 15-16 reps per set, there's a decrease in strength gains. That leaves 70-80%, or 8-12 reps, as the best range for building strength while avoiding injury.

How many reps do you usually do in your strength training workouts? Leave a comment and tell us about it.

If you're interested in learning more about the basics of weight training, you can check out Weight Training 101 or, if you really want an in-depth class, sign up for this 9-week email course, Beginner's Guide to Strength Training.

February 20, 2009 at 10:55 am
(1) Leon says:

I usually work in the 8 to 10 rep range. But at least once a month I increase the weight and work 4 to 6 reps then on the next day I work that body part I lighten up the weight and work in the 20 to 25 rep range.

February 20, 2009 at 11:18 am
(2) jessica says:

No body ever mentions weight lifting for women using the method that swimmers use for long, lean muscles. I use that method lifting light weight, 25 reps, 3 sets.

February 20, 2009 at 1:58 pm
(3) Zoe says:

I swam competitively thru college. We were told NMT 20 reps for endurance strength training and that was only for long distance swimmers. Sprinters used NMT 15 with heavier weights. It could be a variation from coach to coach I suppose. Really, upon recollection – 15 reps was the standard.

February 20, 2009 at 5:15 pm
(4) Michael says:

I do between 6-8 which is between the 80-85% maximum. I like the results from that for myself. I’m a tall guy and find that gives me the best results.

February 20, 2009 at 6:21 pm
(5) Brad says:

This is an interesting article. Anyway, I typically go between 8 to 15 reps on my sets, depending on the exercise, weight load, and goal that day. However, my trainer sometimes has me do tricep pull-downs or bicep pull-ups on the cable rack for a timed period – usually a minute with a reduced amount of weight from my normal training amount. During that minute, it’s not unusual for me to do 25-30+ reps – I’ve learned to pace myself for survival sake. It always produces a “burn” that I can’t describe here in polite terms, however, the strength and endurance gain as a result of timed reps is quite impressive. I’m even starting to see a boost in muscular definition in my arms. It’s all good.

February 21, 2009 at 12:14 am
(6) Fighting Chicken says:

I tend to start at a weight that I can do 3 sets of 8-10 reps (depending on the exercise), then keep using the same weight until I can do 3 sets of 15 reps. When that happens I move up to a weight that i can do 8-10 reps again, and so on. Good or not? I’m not sure but it’s workin for me.

February 21, 2009 at 6:39 am
(7) Wyatt says:

I just got finished with a workout routine that had me lifting weights in the 8-15 range using 3-5 sets (8, 8, 10, 10, 12) or (8, 10, 10, 12) or (8, 10, 12) and these are done in the reverse pyramid method with heavy weight first. Wow, what a great workout and size building. Well, now I am doing the same workout but lifting heavy one week with the sets above and the lifting lite (75%) the next and using the 8-10 reps for 3 sets. I am excited to see how this does!

February 21, 2009 at 8:06 am
(8) colddonkey says:

I do 9 reps at 3 sets. Started out at 15 reps, yrs ago then slid back to 12 reps but now every 6 months I’ll increase the weight and reduce a rep. Once I’m at 8 reps X 3 sets thats where I’ll stay with an occasional weight increase to up my limits.

February 21, 2009 at 1:50 pm
(9) Mike says:

For maximum benefit, regardless of reps, one set per exercise after warmup needs to be performed to failure to stimulate maximum possible nervous system stimulation of growth. each extra set to failure merely breaks down more muscle tissue that will need to be replaced leaving less recovery ability for growth. 8 to 12 reps is good, slightly higher for leg work. RIP Mike Mentzer

February 21, 2009 at 2:47 pm
(10) dtecum says:

I find that strength, stamina and endurance is more important to me not size. I do 10-12 reps but hold each contraction or extension for a count of 7, for 3 sets.

February 21, 2009 at 4:45 pm
(11) jason says:

As being a trainer and worked with many different types of client the reps and set comes down to the persons overall fitness goals, what i found is usually 15-20reps at the rite intensity and resitance has worked the best. Im not a big believer on lighter weight more reps, comes down to proper weight with proper resistence will get the results you want…theres many more factors that play a part….enjoy and keep staying in shape.

February 21, 2009 at 4:49 pm
(12) jason says:

sorry about this i recommend using 15-20reps with only 2 sets(thats rite 2 sets) if doing it rite its enough…..

February 22, 2009 at 2:30 am
(13) Anders Lönn Wege says:

I do three sets with different number of reps and weights. I do 15 reps on set 1, 11 reps on set 2 and 6 reps on set 3. And at my current level that gives 12,5kg on first set 15kg on second set and 17,5kg on third set, per dumbbell while doing benchpress. (I don’t know if there is another name for that exercise since English is not my primary language.)

February 22, 2009 at 12:08 pm
(14) cassandra clark says:

I’m a 42 year old woman.I’m trying to lose weight and gain definition, 20-25 reps is proving great results.

February 22, 2009 at 6:34 pm
(15) ae says:

more than 15 reps you are building muscular endurance, but not really building strength.

February 23, 2009 at 8:53 am
(16) Kim says:

8 reps seldom feel like ENOUGH, its just too much weight if I’m struggling at 8. I aim for 12-15 reps. If its too easy still at 15 then I know it’s time to increase the weight. This is generally what I’ve been taught by several trainers and it works for me wonderfully.

February 23, 2009 at 5:52 pm
(17) Leo says:

I’m a five set guy, with 3 sets using the 8-12 rep system. My last 2 sets are much heavier and I am happy to get 3 reps with the last 2 sets. Most people do not believe me when I tell them I am 53 years old. I have been lifting weights since I was 13, but I think you have to find what works best for you, no two bodies are alike.

February 24, 2009 at 11:53 am
(18) Fitdaddy says:

I have lifted for years and now that I am into my mid-50′s I have to be careful about my joints. I love to lift heavy and used the 12-15 reps 3-4 sets routine for years. However, in recent months, due to joint issues, and frankly some boredom issues, I started trying 20-25 reps at lighter weights. Tone and definition have improved significantly in under a month. Now some might say you have just changed your routine and tricked your muscles, but I have changed-up my routine in the past and never got these results. Good luck to all with your workouts.

February 25, 2009 at 2:11 pm
(19) Art says:

I do ONE Set of 20 Reps, this gets me out of the weight room in about a half hour, 2 times a week, winter, rarely bother with weights in the summer when I’ll bike, run, or swim. I also yoga three time week for a half hour. Weight training has the least priority after areobic, and flexibility. Not bad for a 25 yr old dyslexic.

May 25, 2009 at 2:57 am
(20) Mayan Fox says:

4-8 reps will have you recruiting your fast twitch muscle fibres which will in turn produce greater hypertrophy results as well as strength and power. Think of a sprinters body as opposed to a marathon runner. What you see is the result of those fast twitch fibres having been utilised. Why start exhausting your muscles 1/2 way through a set because of light weights when you can be working them hard from the start. The only exception is abs, calves & upper lats which are predominantely slow twitch fibres so need higher reps to really get them working.

February 11, 2010 at 12:40 am
(21) Jose says:

I do a single set of up to 25 reps of each exercise except abs. When I am able to do 25 reps 3 workouts in a row, I increase the weight by a small amount at the next workout. If I can still do that weight 25 times then I do that for 3 workouts. Eventually I get to a weight that I can’t do 25 reps. … So basically I find a weight where I get to muscle fatigue. Then I work up to 25 reps at that weight and repeat the cycle.

I keep reading in here that that won’t give you strength but mainly endurance. However, if I keep being able to pick up larger and larger weights 25 times I don’t see how I’m not gaining strength. Maybe I won’t get huge muscles but I don’t care about that. Just want to get strong. And my muscles do feel bigger than before I started strength training.

September 21, 2012 at 1:37 am
(22) Steve W. says:

At 60, protecting my joints is key. Pushing big weights to the point of failure will sooner or later end with an injury, so the question is how to push the muscle without over-stressing the connective tissue. I’ve found that starting with an easy warmup set with plenty of reps, usually 12 to 15, then a medium set with 10 to 12, then a harder set with 10 to 12, and a very hard set with 6 to 8 reps. Then my last set would be 6 hard reps again, followed immediately with 6 reps at a lighter weight, then 6 more reps at a lighter weight, then, with an even lighter weight, as many reps as is required to feel pumped. I never push myself to the point of failure however because it causes too much damage to the muscle. The reps should be slow, smooth, always in control, and never strained. Using this method has given me excellent results without injury, and I’m usually fully recovered and ready to work the same muscles again two days or three days later. One other thing, I limit the number of exercises I do, so that I don’t exhaust my entire body. One of the biggest mistakes people make (and one of the main reasons people stop making gains) is because they over train. Old or young, your body can only handle so much.

February 15, 2013 at 6:17 pm
(23) StrengthCoach96 says:

Periodize. Periodize. Periodize. Cycling varying intensities on different days provides maximum results, whether 3×10-15 or 5×5 or pyramids, etc.

There is a point of diminishing returns with high-rep training since each rep is about a 2.5% decrease in intensity, so by the time 20+ reps come around, the intensity level is at 50% or less – basically going through the motions which does not allow the exerciser to reap the benefits of resistance training. If high-rep training was a viable training method, then gum chewers would have skinny faces.

While injury rates increase with low-rep, high-intensity training (typically strains), overuse and repetitive use injuries also occur with high-rep training, such as tendonitis, bursitis, fascitis, etc.

February 18, 2013 at 8:09 am
(24) glelvis says:

10-15 reps works great for me. Heavier weight and fewer reps seems to be much harder on the joints. 3-4 reps as needed. When i’m failing at 8, it’s time to move on.

April 24, 2013 at 5:56 pm
(25) troy says:

I’m 15 years old iv been lifting for over a year now and I tend to do more weight and less reps but iv recently noticed my muscle gain has dramatically slowed down I use 15kg dumbells about 5 reps and 35kg on barbell bicep curl up to 10 reps what can I do to improve

May 18, 2013 at 6:56 pm
(26) Trevor says:

I used to do a 3-5 sets 6-8 reps routine but I got to the point where I was feeling like the reps were getting in the way of my strength gains. For the last month and a half or so I have been doing 3-5 sets 5-7 reps. If I cannot do at least 5 reps on my 3rd set, I do a superset with roughly half the weight for 5-7 reps (no rest period between the two sets). Even though I lower the weight for the superset, I am working at roughly the same intensity because my muscles are already tired from the previous set I could not do 5 reps of. I am mostly seeing great strength gains. My first trainer had me on a 3 set 6-8 rep routine but my last trainer had me on a 20 rep routine for warm-up sets and then 10 rep sets for working sets. He was a bodybuilder which I don’t want to be. Eventually, I want to get into powerlifting. I am a long ways from that though.

May 24, 2013 at 12:11 pm
(27) Norma Padro says:

I had ten years experience working out with one set. It was very nice, because I got the results I wanted. I was toned and I had the energy I needed to keep.

I couldn’t get into the heavy lifting since I’m asthmatic and have a heart condition. I was able to do reps with light weight until my muscles were tight then go on to another exercise.

I never counted the reps, because I focused on the muscles working. There were days when the muscles were too tight to even contract or lift at all. I guess I must have used the muscle on something else.

An example. I am focusing on upper body exercise. One exercise like bench press. This exercise works all the upper body parts. To see if the theory still works. I tried doing military press with my little 3pound dumbell. I couldn’t push it up at all. The muscle wasn’t working.

I had exhausted the arm muscles by doing chest presses with my elastic band. I tried doing a dumbell curl with the same dumbell and nothing. I couldn’t curl at all. I didn’t even try.

I’m staying with one set, because this works for my muscles. I recommend one set for upper body like bench press, lower body squats. Sometimes the abs get too tight to even do any crunches. I guess it’s not always needed.

This works out well for me.

October 28, 2013 at 9:49 pm
(28) michael says:

What you failed to address is the level which you are starting from. Studies show that beginners can achieve strength gains with as low as 40% of the 1RM. The higher level person will require a higher percentage of their 1RM.

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