Effects of different small-sided games on blood lactate and GH/IGF-1 axis responses in young soccer players

Soccer and its intense workouts cause lactate accumulation and extensive metabolic changes. This study, therefore, aimed to compare the percentage of maximum heart rate (%HRmax), blood lactate, growth hormone (GH), and insulin-like growth factor-1 (IGF-1) responses across different formats of small-sided games (SSG) in young soccer players. Twenty-four soccer players (mean age: 17.1 +/- 1.12 years, weight 67.28 +/- 1.65 kg and body mass index 20.8 +/- 1.18 kg/m(2)) were randomly divided into three equal groups, including control, 2 vs. 2 (8 periods of 2 min separated by 1 min of passive recovery, with a pitch of 20 m x 25 m) and 4 vs. 4 (4 periods of 4 min separated by 2 min of passive recovery, with a pitch of 28 m x 35 m). Blood samples were taken immediately before and after small-sided games. The results showed that the heart rate increased significantly in young soccer players at different minutes of SSG (p <= 0.05). The comparison of these two SSG did not show any significant differences on lactate and somatotropic hormone concentrations (p > 0.05), although each alone significantly increased lactate, GH and IGF-1 levels compared to control group (p < 0.05). Hence, it can be concluded that due to the sufficient intensity of these two modes of SSG, the cellular relationship between the GH/IGF-1 axis and lactate helps improve the physiological capacity of young soccer players. However, further studies were needed to consider more accurate effects of these variables (lactate, GH and IGF-1) with two SSG modalities (2 vs. 2 and 4 vs. 4).