Many beginners believe that high number of repetitions performed with light weights will tone the body and add definition to the muscles.
Actually, the truth is there is no such thing as muscle toning.The tone that people often desire is just a small growth in the size of the muscles and it has everything to do with low bodyfat percentage.Also, certain exercises cannot shape the muscles in a certain way. The muscle will grow and shape according to your genetic profile.High reps help you build muscle endurance,but do not tone the muscles and certainly don’t make the muscle stronger.
High reps will cause sarcoplasmic hypertrophy, which means that you’ll get an increase in volume of the non-contractile fluids of the muscle, the sarcoplasm. This fluid will make you bigger, but won’t give your muscles any definition. You won’t get a lot stronger either.The bad news here is that sarcoplasm is only about 25% of the muscle mass, or in other words – you’ll get a little bigger and bloated but not toned or defined.
Myofibrillar hypertrophy on the other hand is a result of training with heavy weights and low repetitions. It is an increase in the number of muscle fibres in the muscle. Myofibrillar hypertrophy makes the muscle harder, stronger and more dense.
In conclusion : The tone and definition that people desire is not a product of high reps and low weights. It is a product of hard training with heavy weights in combination with a sensible diet and cardio training.