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Background and aims: This study assessed the reliability of evaluating asymmetrical strength and power deficits in the lower limbs of healthy middle-aged, healthy older and mobility-limited elders. We also explored the relationship between limb asymmetry and physical functioning. Methods: We evaluated baseline knee extension strength and power asymmetry data from a cohort of older adults (n=57; 74.2±0.9 yrs, 26 male) who participated in a lower body strength training study (TS) and from a cross-sectional study of community dwelling volunteers. Cross-sectional participants were recruited into: healthy middle-aged (MH) (n=31-, 47.4±4.8 yrs, 14 male), healthy older (OH) (n=28; 74.0±3.6 yrs, 16 male) and mobility-limited older (OML) (n=34; 77.8±4.5 yrs, 16 male) groups. Knee extensor strength (1RM) and power asymmetry at 40% and 70% of 1RM were evaluated for test-retest reliability using intraclass correlation coefficients (ICCs). Results: Knee extension 1RM, and peak power at 40% and 70% asymmetry ICCs exhibited excellent to good reliability in the TS and OML groups (TS= 0.8, 0.7and 0.7, respectively; OML= 0.7, 0.7, and 0.9. respectively) but not in the MH and OH groups. No consistent association between lower limb asymmetry and measures of physical functioning was observed. Conclusions: Assessment of lower limb strength and power asymmetry is more reliable in mobility-limited elders when compared to healthy middle-aged and older subjects. The relationship of lower limb asymmetry to physical functioning is poor, in contrast to associations between the absolute strength and power of the individual limbs and physical functioning. [ABSTRACT FROM AUTHOR]

Background and aims: This study investigated whether high-velocity high-power training (POW) improved lower extremity muscle power and quality in functionally-limited elders greater than traditional slow-velocity progressive resistance training (STR). Methods: Fifty-seven community-dwelling older adults aged 74.2±7 (range 65-94 yrs), Short Physical Performance Battery score 7.7±1.4, were randomized to either POW (n=23) (12 females), STR (n=22) (13 females) or a control group of lower extremity stretching (CON) (n=12) (6 females). Training was performed three times per week for 12 weeks and subjects completed three sets of double leg press and knee extension exercises at 70% of the one repetition maximum (1RM). Outcome measures included 1RM strength and peak power (PP). Total leg lean mass was determined using dual-energy X-ray absorptiometry. to estimate specific strength and specific PP. Results. During training, power output was consistently higher in POW compared to STR for knee extension (~2.3-fold) and leg press (~2.8-fold) exercises (p<0.01). Despite this, PP and specific PP of the knee extensors increased similarly from baseline in POW and STR compared to CON (p<0.01), and no significant time-group interaction occurred for PP of the leg extensors. However, gains in leg press specific PP were significantly greater in POW compared to both STR and CON (p<0.05). Total leg lean mass did not change within any group. Conclusions: A short-term intervention of high-velocity power training and traditional slow-velocity progressive resistance training yielded similar increases of lower extremity power in the mobility-impaired elderly. Neuromuscular adaptations to power training, rather than skeletal muscle hypertrophy, may have facilitated the improvements in muscle quality. Additional studies are warranted to test the efficacy of power training in older individuals with compromised physical functioning. [ABSTRACT FROM AUTHOR]

Background and aims: The purpose of this study was to assess the reliability and concurrent validity of a new methodology to evaluate lower extremity muscle power in older, functionally limited men and women. Methods: A cross sectional evaluation was performed on 58 older men (n=27) and women (n=31) (74.2±0.9 years). Knee and hip (leg press) and knee extensor power were evaluated on pneumatic and isokinetic resistance equipment. Incremental single attempt power (IP) testing utilized a single attempt at attaining maximum power at each of six external resistances and was compared to multiple attempt pneumatic power (MP) testing determined by the highest of 5 attempts at achieving maximum power at two set resistances and also with power determined by isokinetic dynamometry. Results: Leg press extension MP yielded significantly greater power than IP at both low (mean=225.3±11.85 and 183.9±11.52 watts respectively, p<0.001) and high (mean=249.7±15.25 and 201.7±13.18 watts respectively, p<0.001) external resistances. Knee extension MP also produced significantly greater power when compared to IP at low (mean=82.4±4.45 and 69.7±4.28 watts respectively, p<0.001) and high (mean=93.7±6.3 and 83.2±5.93 watts respectively, p<0.001) external resistances. MP testing exhibited excellent reliability at both low (leg press extension: Intra Class Correlation (ICC)=0.93, knee extension: ICC=0.87) and high (Leg press extension: ICC=0.85, Knee Extension: ICC=0.91) external resistances. MP knee extension at 70% 1 RM also showed good agreement with average isokinetic power (R²=0.636). Conclusions: These findings support the reliability and concurrent validity of MP for the evaluation of muscle power in older individuals. [ABSTRACT FROM AUTHOR]