Schizophrenia is a serious mental disease characterized by a combination of positive and negative symptoms, and it is associated with social and occupational dysfunction. The positive symptoms reflect an excess or distortion of normal functions (delusions, hallucinations and disorganized behavior), whereas the negative symptoms are related to flattened affect, alogia, avolition and decreased cognitive function. One recent study reported that schizophrenia is associated with distortions of reality, changes in perceptions and thoughts, difficulties in social situations and problems with daily functions.
Schizophrenia generally appears at the end of adolescence or at the beginning of adulthood and affects approximately 1% of the population. The disease has a deteriorating course and does not involve large neurological changes. Its etiology may be explained by interactions between factors associated with genetic susceptibility and adverse environmental factors. Recently, it has been hypothesized that alterations in neuroplasticity may be an important factor for the development of schizophrenia.
IGF-1 is an important growth factor that induces neuroplasticity (neuronal survival, cell differentiation, cell proliferation, synaptic plasticity and neurogenesis). Schizophrenic patients have lower serum IGF-1 levels than healthy individuals. Because IGF-1 levels are lower in schizophrenic patients and this is associated with the etiology of the disease, it is important to investigate treatments that may increase serum IGF-1. Antipsychotic drugs such as olanzapine stimulate the phosphorylation of AKT, which is part of the main downstream pathway of IGF-1. It is possible to activate AKT through several intracellular signals and receptors, including activation of the insulin receptor (IR). However, activation of the IGF-1 receptor (IGF-1R) appears to be the main activator of AKT phosphorylation.
In addition to antipsychotic medications, resistance exercises may be another way to increase IGF-1 concentrations. This type of physical exercise has been growing in popularity in society. In recent years, evidence has shown benefits from this exercise for different age groups in both healthy and sick individuals, and it has been indicated to augment bone mineral mass, strength and muscular mass; to prevent or treat sarcopenia; to decrease frailty and functional impairment; and to improve cognitive function and hypertension, among other benefits.
Studies conducted with the young and the elderly who underwent resistance training have shown increased serum IGF-1 levels. However, studies showing the effects of resistance training and concurrent training on schizophrenia and serum IGF-1 levels have not been performed. Studying physical exercise is important for several reasons. Importantly, it is a low-cost treatment that may be a possible therapeutic tool, not only to increase IGF-1 concentrations but also to decrease disease symptoms, especially negative symptoms, and the side effects of antipsychotic drugs (extrapyramidal effects, weight gain and tiredness), which may improve quality of life. Therefore, the aim of this study is to evaluate the effects of 20 weeks of resistance training and concurrent training on psychotic and depressive symptoms, quality of life and serum IGF-1 concentration.
