Association between intramuscular fat in the arm following arm training and INSIG2.

Insulin-induced gene 2 (INSIG2) single-nucleotide polymorphism (SNP rs7566605) is linked to lipid metabolism, and this study assessed its potential influence on fat in the upper arm following arm training. Twenty healthy sedentary volunteers (22.0 ± 1.1 years, body mass index 25.4 ± 4.0 kg/m(2) ; mean ± standard deviation) carried out a 12-week two-arm elbow extensor training (10 maximal extensions with 1 min recovery between bouts) five times per day, five times per week. For 17 volunteers, upper arm muscle and adipose tissue [subcutaneous (SCAT) and intramuscular (IMAT)] volumes were evaluated by magnetic resonance imaging before, immediately after, and 12 months after training and variables were related to the subjects' INSIG2 SNP rs7566605 genotype. Muscle volume and SCAT for the upper arm, as the decrease in IMAT during training were not related to INSIG2 SNP rs7566605: GG: %IMAT 1.0 ± 0.9%; GC/CC: %IMAT 0.6 ± 0.5% (P > 0.05). However, in the year following the training, accumulation of upper arm IMAT was twice as large in participants homozygous for the G allele (GG: Δ%IMAT +2.5 ± 0.8%; GC/CC: Δ%IMAT +1.1 ± 0.7%; P < 0.01). This study suggests that the G allele in the INSIG2 SNP rs7566605 is more relevant for changes in IMAT following training than for the amount of subcutaneous fat.

Assessment of elbow extensors endurance in young athletes.

The aim of this study was to compare different endurance parameters of elbow extensors between senior and junior athletes. A group of 23 junior (16.2 ± 0.8 years, BMI 21.8 ± 2.9 kg/m(2)) and 16 senior athletes (23.1 ± 6.2 y, BMI 23.6 ± 4.2 kg/m(2)) volunteered for the study. Strength measurements were performed on the isoacceleration dynamometer (5 sets of 10 maximal elbow extensions, 1 min resting period between each set). The following strength parameters were measured: maximal strength (MS), endurance strength (ES), fatigue rate (FR) and decrease in strength (DS). Both arms triceps brachii muscle mass (MM) was calculated using a series of cross-sectional images of upper arms obtained by the MRI. Triceps brachii muscle mass for both arms in senior athletes showed significantly higher values (1286.9 ± 323.7 g) compared to young athletes (948.9 ± 171.1 g, p<0.01). ES was 50% higher in seniors, while FR was 10% higher in juniors. MS was 35% higher in seniors, but no difference was discovered when this parameter was expressed in relation to muscle mass. DS was significantly different between juniors and seniors, except in absolute values. No significant correlation was found between triceps brachii muscle mass and FR or DS. Different values of strength decrease throughout multiple contractions could be attributed to different characteristics of various sports.