The Effect of Plyometric and Combined Training on IGF-1 and MGF Responses in Vastus Lateralis Muscle in Non-Athlete Men

Insulin – like growth factor – I (IGF-1) plays a role in the skeletal muscle in the development، growth، repair، and maintenance of the tissues in an autocrine / paracrine as well as endocrine fashion. The aim of the present study was to investigate the response of growth factors to two different training methods. 14 male volunteers were selected and divided randomly into two groups. Group A (plyometric، 7 subjects، age: 20. 86±1. 86 yr، height: 179. 29±4. 23 cm، weight: 74. 56±6. 24 kg) performed plyometric training and group B (combined، 7 subjects، age: 21. 43±1. 72 yr، height: 181. 71±6. 42 cm، weight: 76. 14± 8. 47 kg) performed a combination of resistance training and plyometric training 3 days per week for 8 weeks (4 weeks of resistance training and 4 weeks of plyometric training). Muscle biopsies were obtained from vastus lateralis muscle 3 days before and 7 days after the training. To evaluate muscle power، Bosco (5 and 60 sec.)، Sargent jump and standing long jump tests and to evaluate agility and speed، hexagonal obstacle and 35m dash tests were used respectively. To estimate gene expression of insulin – like growth factor (IGF-1) and mechanical growth factor (MGF)، real time RT – PCR was performed. Paired and independent t tests were used to analyze the data at (P≤ 0. 05). The results showed that in Bosco، Sargent jump، standing long jump، hexagonal obstacle and 35m dash tests، plyometric group had better results than group B. The MGF gene expression decreased insignificantly in group A (by 20. 18%، P≤0. 29) and increased significantly in group B (by 159. 24%، P≤0. 048). IGF-1 gene expression increased significantly in group A (by 133. 83%، P≤0. 04) and increased insignificantly in group B (by 24. 06%، P≤0. 16). It can be concluded that different IGF-1 transcripts (IGF-IEa and MGF) differently respond to various mechanical and metabolic overload strategies in human skeletal muscle.