Isometric Strength Of Leg Extensors Research Articles

Effects of Resistance Training Cessation on Cycling Performance in Well-Trained Cyclists: An Exploratory Study.

Bláfoss, R, Rikardo, J, Andersen, AØ, Hvid, LG, Andersen, LL, Jensen, K, Christensen, PM, Kvorning, T, and Aagaard, P. Effects of resistance training cessation on cycling performance in well-trained cyclists: an exploratory study. J Strength Cond Res 36(3): 796-804, 2022-Supplementary (i.e., concurrent) resistance training can enhance cycling performance among competitive cyclists. However, a lack of knowledge exists about the retention (decay profile) in mechanical muscle function and cycling performance after concurrent resistance and endurance training. The present exploratory intervention study investigated the effect of 6 weeks of resistance training cessation when preceded by 8 weeks of concurrent resistance and endurance training on mechanical muscle function and cycling performance in 9 male well-trained competitive cyclists (V̇o2max = 66 ± 7 ml·min-1·kg-1). Cyclists performed periodized resistance training targeting leg and core muscles for 8 weeks as a supplement to their normal endurance (cycling) training. This was followed by 6 weeks of endurance training only (retention period) leading up to the start of the competitive season. Maximal leg extensor power, isometric leg extensor strength (maximal voluntary contraction [MVC]), rate of force development (RFD), and long-term cycling performance (2-hour submaximal cycling at 55% of Wmax), followed by 5-minute max cycling were evaluated. After 8 weeks of concurrent resistance and endurance training, leg extensor power, MVC, and RFD increased by 12, 15, and 17%, respectively while mean power output (W) during 5-minute max cycling increased by 7% (p < 0.05). Training-induced gains in MVC and 5-minute max cycling power were retained after 6-week cessation of resistance training (p < 0.05). These findings indicate that competitive cyclists can focus on cycling training alone for at least 6 weeks leading up to competition without losing attained gains in maximal muscle strength and cycling performance achieved by preceding periods of concurrent resistance training.

Heterogeneity of the strength response to progressive resistance exercise training in older adults: Contributions of muscle contractility.

Older adults display wide individual variability (heterogeneity) in the effects of resistance exercise training on muscle strength. The mechanisms driving this heterogeneity are poorly understood. Understanding of these mechanisms could permit development of more targeted interventions and/or improved identification of individuals likely to respond to resistance training interventions. Thus, this study assessed potential physiological factors that may contribute to strength response heterogeneity in older adults: neural activation, muscle hypertrophy, and muscle contractility. In 24 older adults (72.3±6.8years), we measured the following parameters before and after 12weeks of progressive resistance exercise training: i) isometric leg extensor strength; ii) isokinetic (60°/sec) leg extensor strength; iii) voluntary (neural) activation by comparing voluntary and electrically-stimulated muscle forces (i.e., superimposed doublet technique); iv) muscle hypertrophy via dual-energy x-ray absorptiometry (DXA) estimates of regional lean tissue mass; and v) intrinsic contractility by electrically-elicited twitch and doublet torques. We examined associations between physiological factors (baseline values and relative change) and the relative change in isometric and isokinetic muscle strength. Notably, changes in quadriceps contractility were positively associated with the relative improvement in isokinetic (r=0.37-0.46, p≤0.05), but not isometric strength (r=0.09-0.21). Change in voluntary activation did not exhibit a significant association with the relative improvements in either isometric or isokinetic strength (r=0.35 and 0.33, respectively; p>0.05). Additionally, change in thigh lean mass was not significantly associated with relative improvement in isometric or isokinetic strength (r=0.09 and -0.02, respectively; p>0.05). Somewhat surprising was the lack of association between exercise-induced changes in isometric and isokinetic strength (r=0.07). The strength response to resistance exercise in older adults appears to be contraction-type dependent. Therefore, future investigations should consider obtaining multiple measures of muscle strength to ensure that strength adaptations are comprehensively assessed. Changes in lean mass did not explain the heterogeneity in strength response for either contraction type, and the data regarding the influence of voluntary activation was inconclusive. For isokinetic contraction, the strength response was moderately explained by between-subject variance in the resistance-exercise induced changes in muscle contractility.

Physical Fitness and Cognitive Function in an 85-Year-Old Community-Dwelling Population

Background: Little is known about the association between physical fitness and cognitive function in very elderly people (over 80 years of age). Objectives: To evaluate that relationship in 85-year-old community-dwelling individuals. Methods: Out of 207 participants (90 males, 117 females) who were 85 years old and community-dwelling, 205 completed the Mini-Mental State Examination (MMSE) for evaluating cognitive function. The numbers of subjects who completed physical fitness measurements such as hand-grip strength, isometric leg extensor strength, one-leg standing time, stepping rate, and walking speed were 198, 159, 169, 168, and 151, respectively. Results: There were significant associations in MMSE with hand-grip strength (right or left hand), isometric leg extensor strength, stepping rate, and walking speed by simple regression analysis. MMSE was still significantly associated with hand-grip strength (β = 0.305, p = 0.005 for right side; β = 0.309, p = 0.004 for left side), stepping rate (β = 0.183, p = 0.046), and walking speed (β = –0.222, p = 0.014) by multiple regression analysis after adjustments for the amount of education, gender, smoking, drinking, complication of stroke, body weight, body height, regular medical care, serum albumin, blood HbA1c, and marital status. By logistic regression analysis, the prevalence of a normal MMSE score (MMSE ≧24) was increased by 9% with each 1-kg increase in hand-grip strength of the left hand (OR 1.087, 95% CI 1.003–1.179, p = 0.042), and was increased by 6% with each step per 10 s in stepping rate (OR 1.060, 95% CI 1.000–1.122, p = 0.048). Conclusion: In a very elderly population of 85-year-olds, cognitive function was associated with some physical fitness measurements, independent of confounding factors.

Physical Fitness and 4-Year Mortality in an 80-Year-Old Population

Because little is known about the relationship between physical fitness and mortality among very elderly people, we evaluated this association in a Japanese population of 80-year-old community residents. Among 1282 80-year-old residents of Fukuoka Prefecture, Japan, 697 individuals (277 men and 420 women) underwent physical fitness tests of handgrip strength, isometric leg extensor strength, isokinetic leg extensor power, stepping rate, and one-leg standing time. Four years later, the dates and causes of death among the participants during those years were analyzed based on data from resident registration cards and from official death certificates. During the 4-year follow-up period, 107 individuals (58 men and 49 women) died. Of these deaths, 27 were due to cardiovascular disease (CVD), 27 to cancer, 22 to pneumonia, and the rest to other causes. The relative hazard ratios (HR) for all-cause mortality, adjusted for various confounding factors, fell with increases in stepping rate, and the HR for pneumonia mortality fell with increases in leg extensor strength. In contrast, there was no association between cardiovascular or cancer mortality and physical fitness. A partial association was found between impaired physical fitness at the age of 80 years and increased mortality in the 4 years thereafter. Mortality due to all causes was related only to stepping rate, and mortality due to pneumonia was related to leg extensor strength. Mortality due to CVDs or cancers was not associated with physical fitness.

Motor performance deteriorates with simultaneously performed cognitive tasks in geriatric patients

Hauer K, Marburger, C, Oster P. Motor performance deteriorates with simultaneously performed cognitive tasks in geriatric patients. Arch Phys Med Rehabil 2002;83:217-23. Objective: To investigate whether simultaneous cognitive tasks influence maximal motor performance in frail geriatric patients with a history of injurious falls and different levels of cognitive function. Design: Experimental 3-group design. Setting: Geriatric rehabilitation hospital. Participants: Twenty-two healthy, young adults (mean age ± standard deviation, 27.7 ± 9y) and 23 geriatric patients (mean age, 80.9 ± 5.4y) with a history of injurious falls with (Mini-Mental State Examination [MMSE] score, 20.5 ± 1.6) and without (MMSE score, 28.1 ± 1.2) cognitive impairment. Interventions: Not applicable. Main Outcome Measure: Motor performance: peak and integral of maximal isometric strength of leg extensors. Cognition: semiautomated calculation steps (serial 2 forward) and nonautomated calculation steps derived from the MMSE (serial 7 retro). Motor and cognitive performances were examined as single and dual tasks. Results: In frail geriatric patients, especially in patients with cognitive impairment, maximal motor performance decreased significantly during all dual tasks. Cognitive performance was reduced, depending on the task and group. Conclusion: In frail or cognitively impaired geriatric patients, additional tasks can substantially decrease maximal motor performance. Insufficient resources on dual tasking may thus be a link in connecting the high incidence of falls with frailty and cognitive impairment in geriatric patients with a history of injurious falls. © 2002 by the American Congress of Rehabilitation Medicine and the American Academy of Physical Medicine and Rehabilitation