Group Exercise Program. The participants allocated into the GET Group will receive a general exercise training realized in group of workers. Each training session started with a five minute swarm-up by slowly moving the neck, upper back, shoulder, arms and hands through pain-free range of motion; followed by 30 minutes of stretching and strengthening exercises for neck, upper back, shoulder, arms and hands, performed in the standing posture, sitting or lying. For resistance exercise, will be adopted 3 sets of 10 repetitions with a load of 80% of 1 repetitions maximum 12. Dumbbells and elastic bands and will be used as accessories to perform the resistance exercises.

Individual Exercise Program. The participants allocated into the IET Group will receive a individual and specific strength training with seven different exercises, based in training programme describe by Andersen et al. and Sundstrup et al . During the intervention period, the training intensity were progressively increased according to the principle of periodization and progressive overload. Dumbbells and elastic bands and will be used as accessories to perform the resistance exercises. Experienced instructors supervised every other training session.

The participants allocated into the GET Group will receive a general exercise training realized in group of workers. Each training session started with a five minute swarm-up by slowly moving the neck, upper back, shoulder, arms and hands through pain-free range of motion; followed by 30 minutes of stretching and strengthening exercises for neck, upper back, shoulder, arms and hands, performed in the standing posture, sitting or lying. For resistance exercise, will be adopted 3 sets of 10 repetitions with a load of 80% of 1 repetitions maximum. Dumbbells and elastic bands and will be used as accessories to perform the resistance exercises.

Numeric Pain Rating Scale (NPRS) assesses the pain intensity levels perceived by the patient using likert 11-point scale (ranging from 0 to 10), with 0 representing "no pain" and 10 representing "the worst possible pain". The participants will be instructed to report the level of pain intensity in the last seven days.

The Global Perceived Effect Scale assesses the patient's perception, on a numerical scale, about how much their condition has improved or deteriorated comparing the onset of symptoms to the last few days. It is an 11-point numerical scale ranging -5 to +5, where the negative scores means that the patients are worsening, and the positive scores means refer positive that patients are recovering compared to the beginning. This scale has adequate clinimetric properties and it has been recommended for use as outcome measure for chronic pain trials 15.