The effects of nonlinear resistance and aerobic interval training on serum levels of apelin and insulin resistance in middle-aged obese men

Apelin is an adipokine which may contribute to the link between obesity and metabolic diseases. Regular exercise training has been proposed as a strategy for reducing the risk of these diseases by positive adaptations in adipokines, but there is limited research directly comparing different types of training. The purpose of this study was to determine and compare the effects of nonlinear resistance training (NRT) and aerobic interval training (AIT) on serum levels of apelin-13 and insulin resistance in middle-aged obese men. This quasi-experimental study was conducted from October to February 2012 in Ilam City, Iran. Eligible subjects (33 obese men) between aged 34-46 years participated in this study and were allocated to the following groups: NRT (n= 12), AIT (n= 10), and control (n= 11). The inclusion criteria were sedentary (less than 60 minutes physical activity per week), nonsmokers, no regular exercise for at least the past 6 months, no regular consumption of medication, no special diet, percentage body fat > 23% and no history of medical conditions that would prevent them from participating in the exercise intervention. Only the subjects who performed more than 90% of the training sessions were included in this study. The experimental groups performed 3 weekly sessions for 12 weeks, whereas the control group maintained a sedentary lifestyle. NRT consisted of 40-65 minutes of weight training at different intensities and with a flexible period. AIT consisted of running on a treadmill (4×4 min at 80-90% maximal heart rate, 3 min recovery intervals). Analysis of variance showed that there were no significant differences betwee n the groups for apelin-13 and insulin resistance at baseline (P> 0.05). Compared to control group, two exercise programs were equally effective at reducing insulin resistance, but apelin-13 levels increased significantly only with the AIT (P= 0.04). After the training, maximal oxygen uptake increased significantly in AIT and NRT compared with control group (both P= 0.001) and in AIT more than NRT (P= 0.001). The practical applications indicate that obese men can use both AIT and NRT exercise programs to reduce insulin resistance. However, the AIT may have better beneficial effects (as indicated by apelin-13) compared to NRT.