In 1983 Richard Edwards wrote a mini review entitled "Needle biopsy of skeletal muscle, a review of 10 years' experience" (Muscle and Nerve,6:676-83,1983). He advocated the use of the needle biopsy technique in the diagnosis of muscle disease, its progress and the effects of treatment. He also took part in the early studies performed on healthy muscles. Since those days the key findings are: Muscle morphology. Relative muscle fibre composition is inherited but the subgroups of type 2a and 2x fibres are dependant upon usage. More activity results in an upregulation of type 2a at the expense of 2x fibres. Resistance training seems not to reduce the number of type 1 fibres, but may increase the over-all relative amount of type 2 myosin. Of note is that type 2 fibres posses twice the capacity for fibre hypertrophy compared to type 1 fibres. More hybrid fibres expressing both type 1 and type 2a myosin may, however, develop with both resistance and endurance training. Fibre type specific metabolic capacity. All human muscle fibre types have the capacity for oxidative and glycolytic metabolism. It is true that the type 1 fibres in muscles from sedentary people have more mitochondria than type 2a and 2x fibres, but the latter fibre types may with usage reach similar mitochondrial enzyme activities as the type 1 fibres (2-4 fold). Fibre type-specific contractile characteristics. There is a close coupling between myosin isoform and speed of contraction and the relatively modest variation observed is likely to be related to isoform pattern of other contractile proteins. Regulation of adaptations. Strength training and the regulation of muscle fibre size is well worked out, but conversion of contractile proteins as myosin or an increase in mitochondrial transport or enzyme proteins are still controversial. It may well be that there are different signalling pathways that are being activated by various physical activities, targeting the same genes.