Lighter weights vs heavier weights?

Heavy weight... the more muscle mass I can have I will burn more calorie. Also when I'm on a diet... I already lose both muscle mass and fat at the same time.

I do like variety.. so once in a while I do light weight..

My personal trainer (who is certified and has been so for 20 years) told me this when I was confused:

Lighter weights, heavier reps burns fat and builds long lean muscles
Heavier weights, lighter reps builds bulk

She has me on 20 lbs. (machines) doing 3 sets of 25 reps and I've lost an inch on my arms and 2 inches off my thighs. :happy:

It depends on what you're trying to do. If you're trying to build muscle you should be using heavier weights and doing fewer reps. If you're trying to tone up without bulking up you want lighter weights with higher reps. Not trying to generalize, but most women are looking to tone, while most men are trying to build mass.

heavier weights will keep your metabolism burning longer.

My personal trainer (who is certified and has been so for 20 years) told me this when I was confused:

Lighter weights, heavier reps burns fat and builds long lean muscles
Heavier weights, lighter reps builds bulk

She has me on 20 lbs. (machines) doing 3 sets of 25 reps and I've lost an inch on my arms and 2 inches off my thighs. :happy:

How much time did it take for you to lose those inches doing those reps/weight?

i do "light" weights with a lot of reps but when trainers say light weights they dont mean weight that it is so light that you could go on for 100 times. light weight should still be heavy enough that when are finished you set, your couldnt do another one. whether you do 10/12/15/25 reps, your muscles should be fatigued at that point. heavy weight with low reps are sometimes the heaviest weight you can lift for 3/4/5 reps. many women use weight that is much too light and dont ge tthe results that they want.

Way too much info but a lot of good stuff on this website

http://www.exrx.net/WeightTraining/Myths.html

High Repetitions Burn More Fat Myth
Performing lighter weight with more repetitions (15-20 reps, 20-30 reps, or 20-50 reps) does not burn more fat or tone (simultaneous decrease of fat and increase muscle) better than a heaver weight with moderate repetitions (8-12 reps). Weight training utilizes carbohydrates after the initial ATP and CP stores have been exhausted after the first few seconds of intense muscular contraction. Typically a set's duration is 20 to 30 seconds. For the average fit person, it requires 20 to 30 minutes of continuous aerobic activity with large muscle groups (e.g. Gluteus Maximus and Quadriceps) to burn even 50% fat; fat requires oxygen to burn. Performing a few extra repetitions on a weight training exercise is not significant enough to burn extra fat and may in effect burn less fat. If intensity is compromised, less fat may be burned when light weight is used with high repetitions. The burning sensation associated with high repetition training seems to be the primary deterrent for achieving higher intensities.

Higher volume weight training (i.e. 3 sets versus 1 set of each exercise) with short rest periods of approximately 1 minutes can stimulate a greater acute growth hormone release (Kraemer 1991, 1993; Mulligan 1996). Growth hormone is lipolytic in adults. It is hypothesized that maximal effort is necessary for optimizing exercise induced secretion of growth hormone. Growth hormone release is related to the magnitude of exertion (Pyka 1992) and is attenuated with greater lactic acidosis (Gordon 1994).

Intense weight training utilizing multiple large muscles with longer rest between sets may also accentuate body lipid deficit by increasing post training epinephrine. Intramuscular triacylgycerol is thought to be an important energy substrate following repeated 30 second maximal exercise with 4 minute recovery intervals (McCartney 1996, Tremblay 1994). Rest periods lasting approximately 4 minutes between maximal exercise exercise of very short duration is required for almost complete creatine phosphate recovery required for repeated maximal bouts (McCartney 1986). Insufficient recovery may compromise the intensity of the exercise and in turn, possibly decrease intramuscular triacylgycerol utilization following anaerobic exercise with significantly shorter rest periods.

For individuals attempting to achieve fat loss for aesthetics, the intensity of weight training can be a double edge sword. When beginning an exercise program, muscle mass increases may out pace fat losses, resulting in a small initial weight gain. Significant fat loss requires a certain intensity, duration, and frequency that novice exercisers may not be able to achieve until they develop greater tolerance to exercise. If an exercise and nutrition program is not adequate for significant fat loss, a lighter weight with higher repetitions may be recommended to minimize any bulking effects, although less fat may be utilized hours later. If an aerobic exercise and nutrition program is sufficient enough to lose fat, a moderate repetition range with a progressively heavier weight will accelerate fat loss with a toning effect. If a muscle group ever outpaces fat loss, the slight bulking effect is only temporary. For a toning effect, fat can be lost later when aerobic exercise can be significantly increased or the weight training exercise(s) for that particular muscle can be ceased altogether. The muscle will atrophy to a pre-exercise girth within months. Higher repetitions training may be later implemented and assessed.

It still may be recommended to perform high repetitions (e.g. 20-30) for abdominal and oblique training. It has been theorized muscular endurance may be more beneficial for lower back health than for muscular strength. Furthermore, moderate repetitions with a greater resistance can increase muscular girth under the subcutaneous fat, particularly in men, who have greater potential for muscular hypertrophy. Increasing the thickness around the waist with existing abdominal fat may further increase bulk, particularly in men who typically have greater intra-abdominal and subcutaneous fat in this area. The abdominal musculature is composed of relatively small muscle mass as compared to the glutes, quadriceps, hamstrings, chest, and upper back. Performing high reps with a lighter resistance should not compromise metabolism or muscle increases, as would performing high reps with light resistance on other, larger muscle groups. See Spot Reduction Myth above.

It is plausible that the high repetition myth was originated and later propagated by bodybuilders that used calorie restrictive diets to shed fat before a contest. Because of their weakened state from dieting, they were unable to use their usual heavier weights. When asked about their use of lighter weights, they explained they were "cutting up" for a contest. This is merely a theory, but it is easy to see how it may have been misunderstood that the lighter weight was used to reduce fat instead of actually being a result of their dietary regime.

Typically with weight training alone, the fat loss is equal to the muscle gain, give or take a few pounds. Certain dietary modification can have much greater impact on fat loss than with weight training alone. The ideal program for fat loss would include the combination of proper diet, weight training, and cardio exercise. Also see study summaries: Weight Training and Diet and Endurance and Weight Training.