Velocity dependence of eccentric strength in young and old men: the need for speed!

2015 ◽  
Vol 40 (7) ◽  
pp. 703-710 ◽  
Author(s):  
Geoffrey A. Power ◽  
Demetri P. Makrakos ◽  
Daniel E. Stevens ◽  
Charles L. Rice ◽  
Anthony A. Vandervoort
Keyword(s):  
Large Range ◽  
Young Men ◽  
Older Men ◽  
Isometric Strength ◽  
Voluntary Activation ◽  
Velocity Dependence ◽  
Younger Adults ◽  
Age Related ◽  
Angular Velocities ◽  
Old Men

Older adults better maintain eccentric strength relative to isometric strength, as indicated by a higher ratio of eccentric:isometric torque as compared with younger adults. The effect of increasing angular velocities (>200°/s) on the age-related maintenance of eccentric strength has not been tested and thus it is unknown whether the eccentric:isometric ratio is velocity dependent in old age. The purpose of this study was to investigate eccentric strength of the ankle dorsiflexors over a large range of lengthening angular velocities in young and older men. Isometric neuromuscular properties were assessed on a HUMAC NORM dynamometer. Nine young (∼24 years) and 9 older (∼76 years) healthy men performed maximal voluntary eccentric contractions at angular velocities of 15–360°/s. Despite near full voluntary activation (>95%), the older men were ∼30% weaker than the young men for isometric strength (P < 0.05). Across all lengthening velocities, older men had a greater eccentric:isometric ratio than young men (P < 0.05). Additionally, there was a velocity dependence of strength in both young and older men: eccentric strength increased as velocity increased up to 120°/s (P < 0.05) and plateaued thereafter. In young and older men, eccentric strength at 15°/s was ∼20% and ∼40% greater than isometric strength (P < 0.05), while at 360°/s eccentric strength was ∼50% and ∼90% greater, respectively (P < 0.05). These findings indicate that with increasing angular velocity, both young and older men have considerable increases in the eccentric:isometric ratio of torque production.

Effect of age on dopaminergic responses to protein feeding

1995 ◽  
Vol 268 (4) ◽  
pp. F613-F625
Author(s):  
N. K. Fukagawa ◽  
L. G. Bandini ◽  
M. A. Lee ◽  
J. B. Young
Keyword(s):  
Young Men ◽  
Elderly Men ◽  
Aldosterone Secretion ◽  
Water Excretion ◽  
Age Related ◽  
Serum Aldosterone ◽  
Protein Feeding ◽  
Old Men ◽  
Induced Changes ◽  
Effect Of Age

Renal excretory responses to protein feeding were compared in nine young (20-26 yr) and nine elderly (70-89 yr) men. Although protein increased excretion of dopamine and serotonin (5-HT, P < 0.001 for both), the basal excretion of dopamine and 5-HT was less in old than young men (P < 0.05). Protein increased sodium and water excretion in the young; responses in elderly for both were less (P < 0.025). Carbidopa markedly suppressed dopamine and 5-HT excretion in both young and old men. Carbidopa also attenuated protein-induced natriuresis and diuresis and raised serum aldosterone levels in the young but not in the old men. These age-related differences in dopamine and 5-HT excretion were not abolished by alterations in dietary NaCl. Thus, although dopamine excretion is decreased overall in elderly men, sodium and water excretion and aldosterone secretion in the old men were unaffected by alterations in dopamine production. These data suggest that impaired protein-induced natriuresis in the old men may be due to limitations in renovascular responses and that, in young men, dopamine and 5-HT may contribute to the protein-induced changes in renovascular function.

Aging does not affect voluntary activation of the ankle dorsiflexors during isometric, concentric, and eccentric contractions

2005 ◽  
Vol 99 (1) ◽  
pp. 31-38 ◽  
Author(s):  
Malgorzata Klass ◽  
Stéphane Baudry ◽  
Jacques Duchateau
Keyword(s):  
Electrical Stimulation ◽  
Compound Muscle Action Potential ◽  
Voluntary Contraction ◽  
Voluntary Activation ◽  
M Wave ◽  
Mechanical Responses ◽  
Age Related ◽  
Angular Velocities ◽  
General Slowing ◽  
Ankle Dorsiflexors

This study examines the age-related deficit in force of the ankle dorsiflexors during isometric (Iso), concentric (Con), and eccentric (Ecc) contractions. More specifically, the contribution of neural and muscular mechanisms to the loss of voluntary force was investigated in men and women. The torque produced by the dorsiflexors and the surface electromyogram (EMG) from the tibialis anterior and the soleus were recorded during maximal Iso contractions and during Con and Ecc contractions performed at constant angular velocities (5–100°/s). Central activation was tested by the superimposed electrical stimulation method during maximal voluntary contraction and by computing the ratio between voluntary average EMG and compound muscle action potential (M wave) induced by electrical stimulation (average EMG/M wave). Contractile properties of the dorsiflexor muscles were investigated by recording the mechanical responses to single and paired maximal stimuli. The results showed that the age-related deficit in force (collapsed across genders and velocities) was greater for Iso (20.5%; P < 0.05) and Con (38.6%; P < 0.001) contractions compared with Ecc contractions (6.5%; P > 0.05). When the torque produced during Con and Ecc contractions was expressed relative to the maximal Iso torque, it was significantly reduced in Con contractions and increased in Ecc contractions with aging, with the latter effect being more pronounced for women. In both genders, voluntary activation was not significantly impaired in elderly adults and did not differ from young subjects. Similarly, coactivation was not changed with aging. In contrast, the mechanical responses to single and paired stimuli showed a general slowing of the muscle contractile kinetics with a slightly greater effect in women. It is concluded that the force deficit during Con and Iso contractions of the ankle dorsiflexors in advanced age cannot be explained by impaired voluntary activation or changes in coactivation. Instead, this age-related adaptation and the mechanisms that preserve force in Ecc contractions appeared to be located at the muscular level.

scholarly journals Differences in the Apparent Metabolic Clearance Rate of Testosterone in Young and Older Men with Gonadotropin Suppression Receiving Graded Doses of Testosterone

2006 ◽  
Vol 91 (11) ◽  
pp. 4669-4675 ◽  
Author(s):  
Andrea D. Coviello ◽  
Kishore Lakshman ◽  
Norman A. Mazer ◽  
Shalender Bhasin
Keyword(s):  
Lean Body Mass ◽  
Body Mass ◽  
Young Men ◽  
Serum Testosterone ◽  
Older Men ◽  
Total Testosterone ◽  
Metabolic Clearance ◽  
Clearance Rates ◽  
Testosterone Levels ◽  
Age Related

Abstract Background: Recently we found that testosterone levels are higher in older men than young men receiving exogenous testosterone. We hypothesized that older men have lower apparent testosterone metabolic clearance rates (aMCR-T) that contribute to higher testosterone levels. Objective: The objective of the study was to compare aMCR-T in older and young men and identify predictors of aMCR-T. Methods: Sixty-one younger (19–35 yr) and 60 older (59–75 yr) men were given a monthly GnRH agonist and weekly testosterone enanthate (TE) (25, 50, 125, 300, or 600 mg) for 5 months. Estimated aMCR-T was calculated from the amount of TE delivered weekly and trough serum testosterone concentrations, corrected for real-time absorption kinetics from the im testosterone depot. Results: Older men had lower total (316 ± 13 vs. 585 ± 26 ng/dl, P &lt; 0.00001) and free testosterone (4 ± 0.1 vs. 6 ± 0.3 ng/dl, P &lt; 0.00001) and higher SHBG (52 ± 3 vs. 33 ± 2 nmol/liter, P &lt; 0.00001) than younger men at baseline. Total and free testosterones increased with TE dose and were higher in older men than young men in the 125-, 300-, and 600-mg dose groups. aMCR-T was lower in older men than young men (1390 ± 69 vs. 1821 ± 102 liter/d, P = 0.006). aMCR-T correlated negatively with age (P = 0.0007), SHBG (P = 0.046), and total testosterone during treatment (P = 0.02) and percent body fat at baseline (P = 0.01) and during treatment (P = 0.004). aMCR-T correlated positively with lean body mass at baseline (P = 0.03) and during treatment (P = 0.01). In multiple regression models, significant predictors of aMCR-T included lean body mass (P = 0.008), percent fat mass (P = 0.009), and SHBG (P = 0.001). Conclusions: Higher testosterone levels in older men receiving TE were associated with an age-related decrease in apparent testosterone metabolic clearance rates. Body composition and SHBG were significant predictors of aMCR-T.

Endothelin-1 vasoconstriction and the age-related decline in endothelium-dependent vasodilatation in men

2011 ◽  
Vol 120 (11) ◽  
pp. 485-491 ◽  
Author(s):  
Christian M. Westby ◽  
Brian R. Weil ◽  
Jared J. Greiner ◽  
Brian L. Stauffer ◽  
Christopher A. Desouza
Keyword(s):  
Young Men ◽  
Older Men ◽  
Endothelin 1 ◽  
Age Related ◽  
Eta Receptor ◽  
Vasomotor Regulation ◽  
Artery Disease ◽  
Potent Vasoconstrictor ◽  
Vasoconstrictor Peptide

ET (endothelin)-1, a potent vasoconstrictor peptide released by the endothelium, plays an important role in vasomotor regulation and has been linked to diminished endothelial vasodilator capacity in several pathologies associated with human aging, including hypertension, Type 2 diabetes and coronary artery disease. However, it is currently unknown whether the decline in endothelial vasodilatation with advancing age is due to elevated ET-1 vasconstrictor activity. Accordingly, we tested the hypothesis that the age-related impairment in ACh (acetylcholine)-mediated endothelium-dependent vasodilatation is due, at least in part, to increased ET-1-mediated vasoconstrictor tone. FBF (forearm blood flow) responses to ACh, SNP (sodium nitroprusside) and BQ-123 (ETA receptor blocker) were determined in 14 young (age, 25±1 years) and 14 older (age, 61±2 years) healthy non-obese men. Additionally, FBF responses to ACh were determined in the presence of ETA blockade. Vasodilatation to ACh was lower (approx. 25%; P<0.05) in the older men (from 4.9±0.2 to 13.9±0.9 ml·100 ml−1 of tissue·min−1) compared with the young men (4.6±0.3 to 17.2±1.0 ml·100 ml−1 of tissue·min−1). There were no differences in FBF responses to SNP between the young (4.8±0.3 to 18.5±0.3 ml·100 ml−1 of tissue·min−1) and older (5.1±0.3 to 17.3±0.8 ml·100 ml−1 of tissue·min−1) men. In the young men, resting FBF was not significantly altered by BQ-123, whereas, in the older men, FBF increased approx. 25% in response to BQ-123 infusion (P<0.05). Co-infusion of ACh with BQ-123 resulted in an approx. 20% increase in the ACh-induced vasodilatation in older men compared with saline. In contrast, FBF responses to ACh were not significantly altered by ETA blockade in the young men. In conclusion, these results demonstrate that ET-1 vasoconstrictor activity contributes, at least in part, to diminished endothelium-dependent vasodilatation in older men.

THE RESPONSE OF INHIBIN TO HUMAN CHORIONIC GONADOTROPHIN IS DECREASED IN SENESCENT MEN COMPARED WITH YOUNG MEN

1989 ◽  
Vol 123 (2) ◽  
pp. R9-R11 ◽  
Author(s):  
U. Fingscheidt ◽  
E. Nieschlag
Keyword(s):  
Old Age ◽  
Sertoli Cells ◽  
Young Men ◽  
Serum Testosterone ◽  
Older Men ◽  
Chorionic Gonadotrophin ◽  
Human Chorionic Gonadotrophin ◽  
Before And After ◽  
Old Men ◽  
Ejaculate Parameters

ABSTRACT Inhibin and testosterone were measured in the serum of young and old men with proven fertility before and after stimulation with human chorionic gonadotrophin (hCG) in order to characterize endocrinological changes in senescence further. While there was a significant increase of both hormones in all young men, there was a decreased response of serum testosterone and an insignificant increase in inhibin in the older men. Although basal hormone levels and ejaculate parameters were not different, hCG stimulation revealed that there were decreased secretory capacities of Leydig as well as of Sertoli cells in old age.

scholarly journals Blunting of AICAR-induced human skeletal muscle glucose uptake in type 2 diabetes is dependent on age rather than diabetic status

2009 ◽  
Vol 296 (5) ◽  
pp. E1042-E1048 ◽  
Author(s):  
John Andree Babraj ◽  
Kristy Mustard ◽  
Calum Sutherland ◽  
Mhari C. Towler ◽  
Shaui Chen ◽  
...  
Keyword(s):  
Type 2 Diabetes ◽  
Young Men ◽  
Older Men ◽  
Age Related ◽  
Skeletal Muscle Glucose Uptake ◽  
Ampk Activity ◽  
Young Subjects ◽  
Extracellular Regulated Kinase ◽  
Amp Activated Protein Kinase

We demonstrated previously that, in healthy young men, 5-aminoimidazole-4-carboxamide 1-β-d-ribofuranoside (AICAR) stimulates human muscle 2-deoxyglucose (2DG) uptake without detectable activation of muscle AMP-activated protein kinase (AMPK) but with extracellular-regulated kinase 1/2 (ERK1/2) activation. We tested whether AICAR stimulates muscle 2DG uptake in healthy older patients with or without type 2 diabetes (T2D). Six healthy young subjects (23 ± 3 yr, BMI 25 ± 2 kg/m−2; means ± SE), eight older subjects (59 ± 4 yr, BMI 28 ± 2 kg/m−2), and eight subjects with T2D (62 ± 4 yr, BMI 27 ± 2 kg/m−2) received a 6-h 2DG infusion (prime 10 mg/kg, 6 mg·kg−1·h−1) and AICAR (10 or 20 mg·kg−1·h−1) from 3 to 6 h. Quadriceps biopsies were taken at 0, 3, and 6 h. We determined 1) 2DG uptake, 2) total AMPKα activity, AMPK, acetyl-CoA carboxylase (ACC), and AS160 phosphorylation, and 3) ERK1/2 phosphorylation. Ten milligrams per kilogram per hour AICAR increased 2DG uptake by 2.9 ± 0.7-fold in young men ( P < 0.001), 1.8 ± 0.2-fold in older men ( P < 0.01), and 1.6 ± 0.1-fold in men with T2D; 20 mg·kg−1·h−1 AICAR increases were 2.5 ± 0.1-fold (older men, P < 0.001) and 2.2 ± 0.2-fold (men with T2D, P < 0.001). At 3-h AMPK activity and AMPK, ACC and AS160 phosphorylation were unchanged, but ERK1/2 phosphorylation increased at both AICAR doses. The fold changes of ERK1/2 phosphorylation and 2DG uptake closely correlated ( R2 = 0.55, P = 0.003). AICAR stimulates muscle 2DG uptake in T2D to the same extent as in healthy age-matched controls, but there is an age-related reduction.

Age-related resistance to skeletal muscle fatigue is preserved during ischemia

2007 ◽  
Vol 103 (5) ◽  
pp. 1628-1635 ◽  
Author(s):  
Linda H. Chung ◽  
Damien M. Callahan ◽  
Jane A. Kent-Braun
Keyword(s):  
Skeletal Muscle ◽  
Fatigue Resistance ◽  
Oxidative Metabolism ◽  
Ischemia Reperfusion ◽  
Age Groups ◽  
Young Men ◽  
The Elderly ◽  
Older Men ◽  
Contractile Properties ◽  
Age Related

During voluntary contractions, the skeletal muscle of healthy older adults often fatigues less than that of young adults, a result that has been explained by relatively greater reliance on muscle oxidative metabolism in the elderly. Our aim was to investigate whether this age-related fatigue resistance was eliminated when oxidative metabolism was minimized via ischemia induced by cuff (220 mmHg). We hypothesized that 1) older men ( n = 12) would fatigue less than young men ( n = 12) during free-flow (FF) contractions; 2) both groups would fatigue similarly during ischemia; and 3) reperfusion would reestablish the fatigue resistance of the old. Subjects performed 6 min of intermittent, maximal voluntary isometric contractions of the ankle dorsiflexors under FF and ischemia-reperfusion (IR) conditions. Ischemia was maintained for the first 3 min of contractions, followed by rapid cuff deflation and reperfusion for 3 additional minutes of contractions. Central activation, peripheral activation, and muscle contractile properties were measured at 3 and 6 min of contractions. Older men fatigued less than young men during FF ( P ≤ 0.02), ischemia ( P < 0.001), and reperfusion ( P < 0.001). During FF, activation and contractile properties changed similarly across age groups. At the end of ischemia, central ( P = 0.02) and peripheral ( P ≤ 0.03) activation declined more in the young, with no effect of age on the changes in contractile properties. Thus age-related fatigue resistance was evident during FF and IR, indicating that differences in blood flow and oxidative metabolism do not explain the fatigue resistance of old age.

An age-related shift in the force-frequency relationship affects quadriceps fatigability in old adults

2004 ◽  
Vol 96 (3) ◽  
pp. 1026-1032 ◽  
Author(s):  
Brian L. Allman ◽  
Charles L. Rice
Keyword(s):  
Electrical Stimulation ◽  
Relaxation Rate ◽  
Old Age ◽  
Maximum Voluntary Contraction ◽  
Young Men ◽  
Force Frequency ◽  
Leftward Shift ◽  
Age Related ◽  
Frequency Relationship ◽  
Old Men

We examined the effect of an age-related leftward shift in the force-frequency relationship on the comparative quadriceps fatigability of nine young (27 ± 1 yr old) and nine old men (78 ± 1 yr old) during low-frequency electrical stimulation. Two different protocols of intermittent trains (6 pulses on, 650 ms off) of electrical stimulation at 25% maximum voluntary contraction were performed by both groups: 1) 180 trains at 14.3 Hz [constant frequency (CF) protocol], and 2) 180 trains at the frequency corresponding to 60% of each subject's force-frequency curve [normalized frequency (NF) protocol; young 14.9 ± 0.4 vs. old 12.7 ± 0.5 Hz; P < 0.05]. The quadriceps of the old men were weaker (∼31%) and relaxation was slower compared with the young men, as assessed by the maximal relaxation rate constant of the 50-Hz tetanus (young 12.1 ± 0.2 vs. old 9.2 ± 0.5 s-1; P < 0.05) and a leftward shift in the force-frequency relationship. The NF protocol revealed a decreased fatigability in the quadriceps with old age (percentage of 1st contraction force remaining at 180th: old 63.4 ± 1.5 vs. young 58.2 ± 1.7%; P < 0.05) that was masked during the CF protocol (old 60.7 ± 1.6 vs. young 58.6 ± 2.3%; P > 0.05). Irrespective of the protocol, the maximal relaxation rate was reduced to ∼73 and ∼57% of the prefatigue value in the young and old men, respectively. The age-related leftward shift in the force-frequency relationship of the quadriceps contributed to an underestimation of the fatigue resistance with old age during the CF protocol. However, when the stimulation frequency used in the NF protocol was adjusted to account for the age-related shift in the force-frequency relationship, the quadriceps muscles of the old men were less fatigable than those of the young men. Thus we suggest that whole muscle fatigability is better examined by electrical stimulation protocols that are adjusted for inter- and intragroup differences in the force-frequency relationship.

Motor unit firing rates and contractile properties in tibialis anterior of young and old men

1999 ◽  
Vol 87 (2) ◽  
pp. 843-852 ◽  
Author(s):  
Denise M. Connelly ◽  
Charles L. Rice ◽  
Martin R. Roos ◽  
Anthony A. Vandervoort
Keyword(s):  
Motor Unit ◽  
Tibialis Anterior ◽  
Tibialis Anterior Muscle ◽  
Young Men ◽  
Contractile Properties ◽  
Firing Rates ◽  
Twitch Contraction ◽  
Age Related ◽  
Motor Unit Firing ◽  
Old Men

The effects of aging on motoneuron firing rates and muscle contractile properties were studied in tibialis anterior muscle by comparing results from six young (20.8 ± 0.8 yr) and six old men (82.0 ± 1.7 yr). For each subject, data were collected from repeated tests over a 2-wk period. Contractile tests included maximal voluntary contraction (MVC) with twitch interpolation and stimulated twitch contractions. The old men had 26% lower MVC torque ( P < 0.01) than did the young men, but percent activation was not different (99.1 and 99.3%, respectively). Twitch contraction durations were 23% longer ( P < 0.01) in the old compared with the young men. During a series of repeated brief steady-state contractions at 10, 25, 50, 75, and 100% MVC, motor unit firing rates were recorded. Results from ∼950 motor unit trains in each subject group indicated that at all relative torque levels mean firing rates were 30–35% lower ( P < 0.01) in the old subjects. Comparisons between young and old subjects’ mean firing rates at each of 10%, 50%, and MVC torques and their corresponding mean twitch contraction duration yielded a range of moderate-to-high correlations ( r = −0.67 to −0.84). That lower firing rates were matched to longer twitch contraction durations in the muscle of old men, and relatively higher firing rates were matched with shorter contraction times from the young men, indirectly supports the neuromuscular age-related remodeling principle.

Age-Related Differences in Muscle Power during Single-Step Balance Recovery

2006 ◽  
Vol 22 (3) ◽  
pp. 186-193 ◽  
Author(s):  
Michael L. Madigan
Keyword(s):  
Muscle Function ◽  
Peak Power ◽  
Muscle Power ◽  
Young Men ◽  
Older Men ◽  
Single Step ◽  
Joint Torque ◽  
Balance Recovery ◽  
Age Related ◽  
The Right

The purpose of this study was to investigate agerelated differences in muscle power during a surrogate task of trip recovery. Participants included 10 healthy young men (19–23 years old) and 10 healthy older men (65–83). The task involved releasing participants from a forward-leaning posture. After release, participants attempted to recover their balance using a single step of the right foot. Muscle power at the hip, knee, and ankle of the stepping limb were determined from the product of joint angular velocity and joint torque. Muscle powers during balance recovery followed a relatively consistent pattern in both young and older men, and showed effects of both lean and age. Interestingly, the effects of age did not always involve smaller peak power values in the older men as expected from the well-documented loss of muscle power with aging. Older men exhibited smaller peak muscle power at the knee and larger peak muscle power at the ankle and hip compared to young men. The increases in muscle power at the ankle and hip may result from a neuromuscular adaptation aimed at improving balance recovery ability by compensating for the age-related loss of muscle function.

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