Research in Sport Medicine and Technology

It is necessary to examine the changes of muscle co-contraction in different percent of fatigue-induced force reduction. The present study aims to investigate the effect of fatigue-induced force reduction of knee extension on muscle co-contraction. Ten healthy and active women aged 26.10±2.99 years performed fatigue protocol including 5 seconds of maximal voluntary isometric contraction (MVIC) of the knee extension and a 5-second rest. Muscle co-contraction was calculated for each subject in the repetitions in which the MVIC force was reduced by 10, 20, 30, 40 and 50% as compared to the pre-fatigue MVIC force. Knee extension force and muscle activity measured by Isokinetic and electromyography apparatus, respectively. The difference between co-contraction of vastus lateralis and medialis in different percentages of force reduction was not statistically significant. The co-contraction of rectus femoris and biceps femoris increased by 40 and 50% of force reduction compared to pre-fatigue co-contraction (P<0.01). Co-contraction of biceps femoris and vastus lateralis increased by 20, 30, and 40%, as well as co-contraction of biceps femoris  and vastus medialis increased 40% of the force reduction, compared to pre-fatigue co-contraction (P <0.05). The results, overall, showed that the change of co-contraction during fatigue is influenced by the selected muscle and the rate of force reduction. This finding can help researchers decide how neuromuscular fatigue effects on muscle co-contraction

Aim: Resistance exercises are suggested as a non-drug treatment to improve the complications of menopause (cognitive-nervous and inflammatory problems). The purpose of this study was to investigate the effect of eight weeks of Circuit resistance training on the serum levels of BDNF and TNF-α in sedentary postmenopausal women.
methods: In this semi-experimental research, 30 postmenopausal women (age 54±3 years, body mass index 27.6±1.97 kg/m2) living in Tehran were randomly selected and assigned to two groups, Circuit resistance training groups (n=15) and control groups (n=15). Circuit Resistance training was performed for eight weeks, three sessions per week including 12 stations for the whole body with an intensity of 40-75%, one maximum repetition in three sets with repetitions between 8-12. 24 hours before and after the intervention, fasting blood was taken to measure BDNF and TNF-a were performed. Repeated measures ANOVA statistical method was used to analyze the data.
Results: In the resistance training group, compared to the control group, there was a significant increase in the levels of BDNF (%13.99) and a significant decrease in the levels of TNF-a (%32.92) (P<0.05).
Conclusion: According to the present study, it seems that low-to-moderate Circuit resistance training with increased BDNF and decreased TNF-a was able to improve cognitive-neural and inflammatory factors in postmenopausal women.