Increased proportion of non-contractile elements can be observed during aging by enhanced skeletal muscle echo intensity (EI). Studies have demonstrated that an increase in rectus femoris EI may affect physical performance. However, it is still unknown whether the whole quadriceps femoris EI (QEI) influences strength, power, and functional capacity of an older population. Therefore, the aim of the present study was to determine the correlation between QEI, the four individual quadriceps portions EI, and muscular performance of older men. Fifty sedentary healthy men (66.1 ± 4.5 years, 1.75 ± 0.06 m, 80.2 ± 11.0 kg) volunteered for the present study. The QEI and EI of the four quadriceps portions were calculated by ultrasound imaging. Knee extension one repetition maximum (1RM), isometric peak torque (PT), and rate of torque development (RTD) were obtained as measures of muscular strength. Muscular power was determined by knee extension with 60 % of 1RM and countermovement jump (CMJ). The 30-s sit-to-stand test was evaluated as a functional capacity parameter. QEI and all individual EI were correlated to functional capacity and power during CMJ (p ≤ 0.05), but rectus femoris EI was not related to knee extension average power (p > 0.05). There were significant correlations between all EI variables, 1RM, PT, and RTD at 0.2 s (p ≤ 0.05), but only vastus medialis EI and QEI were correlated to RTD at 0.05 s (p ≤ 0.05). The results of the present study suggest that QEI is related to muscular power and functional capacity of older subjects, but the EI of some individual quadriceps portions may underestimate the correlations with muscular performance.

The objective of the present study was to evaluate and compare the neuromuscular, morphological and functional adaptations of older women subjected to 3 different types of strength training. 58, healthy women (67?5 year) were randomized to experimental (EG, n=41) and control groups (CG, n=17) during the first 6 weeks when the EG group performed traditional resistance exercise for the lower extremity. Afterwards, EG was divided into three specific strength training groups; a traditional group (TG, n=14), a power group (PG, n=13) that performed the concentric phase of contraction at high speed and a rapid strength group (RG, n=14) that performed a lateral box jump exercise emphasizing the stretch-shortening-cycle (SSC). Subjects trained 2 days per week through the entire 12 weeks. Following 6 weeks of generalized strength training, significant improvements occurred in EG for knee extension one-repetition (1RM) maximum strength (+19%), knee extensor muscle thickness (MT, +15%), maximal muscle activation (+44% average) and onset latency (???31% average) for vastus lateralis (VL), vastus medialis (VM) and rectus femoris (RF) compared to CG (p<0.05). Following 6 more weeks of specific strength training, the 1RM increased significantly and similarly between groups (average of +21%), as did muscle thickness of the VL (+25%), and activation of VL (+44%) and VM (+26%). The onset latency of RF (TG=285?109?ms, PG=252?76?ms, RG=203?43?ms), reaction time (TG=366?99?ms, PG=274?76?ms, RG=201?41?ms), 30-s chair stand (TG=18?3, PG=18?1, RG=21?2) and counter movement jump (TG=8?2?cm, PG=10?3?cm, RG=13?2?cm) was significantly improved only in RG (p<0.05). At the end of training, the rate of force development (RFD) over 150?ms (TG=2.3?9.8?N?s???1, PG=3.3?3.2?N?s???1, RG=3.8?6.8?N?s???1, CG=2.3?7.0?N?s???1) was significantly greater in RG and PG than in TG and CG (p<0.05). In conclusion, rapid strength training is more effective for the development of rapid force production of muscle than other specific types of strength training and by consequence, better develops the functional capabilities of older women.

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