The mechanism(s) of load-induced muscle hypertrophy is as yet unclear, but increasing evidence suggests a role for locally expressed insulin-like growth factor I (IGF-I). We investigated the effects of concentric (CON) vs. eccentric (ECC) loading on muscle IGF-I mRNA concentration. We hypothesized a greater IGF-I response after ECC compared with CON. Ten healthy subjects (24.4 +/- 0.7 yr, 174.5 +/- 2.6 cm, 70.9 +/- 4.3 kg) completed eight sets of eight CON or ECC squats separated by 6-10 days. IGF-I, IGF binding protein-4 (IGFBP-4), and androgen receptor (AR) mRNA concentrations were determined in vastus lateralis muscle by RT-PCR before and 48 h after ECC and CON. Serum total testosterone (TT) and IGF-I were measured serially across 48 h, and serum creatine kinase activity (CK), isometric maximum voluntary contraction (MVC), and soreness were determined at 48 h. IGF-I mRNA concentration increased 62% and IGFBP-4 mRNA concentration decreased 57% after ECC (P < 0.05). Changes after CON were similar but not significant (P = 0.06-0.12). AR mRNA concentration increased (P < 0.05) after ECC (63%) and CON (102%). Serum TT and IGF-I showed little change. MVC fell 10% and CK rose 183% after ECC (P < 0.05). Perceived soreness was higher (P < 0.01) after ECC compared with CON. Results indicate that a single bout of mechanical loading in humans alters activity of the muscle IGF-I system, and the enhanced response to ECC suggests that IGF-I may somehow modulate tissue regeneration after mechanical damage.

Despite similar increases in strength and fat free mass, the VR group decreased difficulty of performing the carry task more than the HR group. These data suggest that larger improvements in DAT may be achieved if frequency of high-resistance training is less than 3 times.wk(-1).

No abstract

The is study examined the effects of 24 wk. of resistance training on mood in healthy but sedentary older adults. 28 participants performed resistance training 3 times per week for 24 weeks. No significant differences were found in mood scores between high and variable resistance groups, and there were no significant interactions between resistance and sex or intervention, or among all three factors. For pooled data, significant improvement was found on measures of Confusion, Tension, Anger, and Total Mood Scores, although not for scores for Fatigue, Vigor, and Depression. Sex differences were found on some subscales, but no significant interactions between sex and resistance training. These findings support the effectiveness of resistance training in improving mood in healthy older adults, although further study is needed to control for effect size, as well as cohort, social, and attentional effects.

ple" (p. 50). Rushton presented a vast array of scientific evidence in his conceptualization, for example, a correlation of .62 between cranial capacity and distance from the equator with 20,000 crania representing 122 ethnically distinguishable populations (Beals, Smith, & Dodd, 1984). Templer and Arikawa (2003) reported a correlation of Ϫ.71 between mean IQ and mean high winter temperature and a correlation of Ϫ.61 between mean IQ and mean low winter temperature with 129 countries. There are alternative explanations to those of Rushton for such findings. To relegate Rushton's theory to the realm of absurdity, however, would neither constitute optimal scientific reasoning nor represent an ideal spirit of scholarly disagreement. REFERENCES