Functional and Morphological Adaptations to Aging in Knee Extensor Muscles of Physically Active Men

It is not known if a physically active lifestyle, without systematic training, is sufficient to combat age-related muscle and strength loss. Therefore, the purpose of this study was to evaluate if the maintenance of a physically active lifestyle prevents muscle impairments due to aging. To address this issue, we evaluated 33 healthy men with similar physical activity levels (IPAQ = 2) across a large range of ages. Functional (torque-angle and torque-velocity relations) and morphological (vastus lateralis muscle architecture) properties of the knee extensor muscles were assessed and compared between three age groups: young adults (30 ± 6 y), middle-aged subjects (50 ± 7 y) and elderly subjects (69 ± 5 y). Isometric peak torques were significantly lower (30% to 36%) in elderly group subjects compared with the young adults. Concentric peak torques were significantly lower in the middle aged (18% to 32%) and elderly group (40% to 53%) compared with the young adults. Vastus lateralis thickness and fascicles lengths were significantly smaller in the elderly group subjects (15.8 ± 3.9 mm; 99.1 ± 25.8 mm) compared with the young adults (19.8 ± 3.6 mm; 152.1 ± 42.0 mm). These findings suggest that a physically active lifestyle, without systematic training, is not sufficient to avoid loss of strength and muscle mass with aging.

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Activation varies among the knee extensor muscles during a submaximal fatiguing contraction in the seated and supine postures

Journal of Applied Physiology ◽

10.1152/japplphysiol.00334.2003 ◽

2003 ◽

Vol 95 (4) ◽

pp. 1515-1522 ◽

Cited By ~ 42

Author(s):

L Rochette ◽

S. K. Hunter ◽

N Place ◽

R Lepers

Keyword(s):

Vastus Lateralis ◽

Maximum Voluntary Contraction ◽

Knee Extensor ◽

Voluntary Contraction ◽

Emg Activity ◽

Task Failure ◽

Rate Of Increase ◽

Extensor Muscles ◽

Seated Posture ◽

Knee Extensor Muscles

Ten young men sustained an isometric contraction of the knee extensor muscles at 20% of the maximum voluntary contraction (MVC) torque on three separate occasions in a seated posture. Subjects performed an isometric knee extension contraction on a fourth occasion in a supine posture. The time to task failure for the seated posture was similar across sessions (291 ± 84 s; P > 0.05), and the MVC torque was similarly reduced across sessions after the fatiguing contraction (42 ± 12%). The rate of increase in electromyograph (EMG) activity (%MVC) and torque fluctuations during the fatiguing contractions were similar across sessions. However, the rate of increase in EMG differed among the knee extensor muscles: the rectus femoris began at a greater amplitude (31.5 ± 11.0%) compared with the vastus lateralis and vastus medialis muscles (18.8 ± 5.3%), but it ended at a similar value (45.4 ± 3.1%). The time to task failure and increase in EMG activity were similar for the seated and supine tasks; however, the reduction in MVC torque was greater for the seated posture. These findings indicate that the time to task failure for the knee extensor muscles that have a common tendon insertion did not alter over repeat sessions as had been observed for the elbow flexor muscles (Hunter SK and Enoka RM. J Appl Physiol 94: 108-118, 2003).

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Knee angle-dependent oxygen consumption during isometric contractions of the knee extensors determined with near-infrared spectroscopy

Journal of Applied Physiology ◽

10.1152/japplphysiol.01420.2004 ◽

2005 ◽

Vol 99 (2) ◽

pp. 579-586 ◽

Cited By ~ 38

Author(s):

C. J. de Ruiter ◽

M. D. de Boer ◽

M. Spanjaard ◽

A. de Haan

Keyword(s):

Oxygen Consumption ◽

Near Infrared ◽

Vastus Lateralis ◽

Knee Extensor ◽

Rectus Femoris ◽

Knee Extensors ◽

Isometric Contractions ◽

Knee Angle ◽

Extensor Muscles ◽

Knee Extensor Muscles

Fatigue resistance of knee extensor muscles is higher during voluntary isometric contractions at short compared with longer muscle lengths. In the present study we hypothesized that this would be due to lower energy consumption at short muscle lengths. Ten healthy male subjects performed isometric contractions with the knee extensor muscles at a 30, 60, and 90° knee angle (full extension = 0°). At each angle, muscle oxygen consumption (mV̇o2) of the rectus femoris, vastus lateralis, and vastus medialis muscle was obtained with near-infrared spectroscopy. mV̇o2 was measured during maximal isometric contractions and during contractions at 10, 30, and 50% of maximal torque capacity. During all contractions, blood flow to the muscle was occluded with a pressure cuff (450 mmHg). mV̇o2 significantly ( P < 0.05) increased with torque and at all torque levels, and for each of the three muscles mV̇o2 was significantly lower at 30° compared with 60° and 90° and mV̇o2 was similar ( P > 0.05) at 60° and 90°. Across all torque levels, average (± SD) mV̇o2 at the 30° angle for vastus medialis, rectus femoris, and vastus lateralis, respectively, was 70.0 ± 10.4, 72.2 ± 12.7, and 75.9 ± 8.0% of the average mV̇o2 obtained for each torque at 60 and 90°. In conclusion, oxygen consumption of the knee extensors was significantly lower during isometric contractions at the 30° than at the 60° and 90° knee angle, which probably contributes to the previously reported longer duration of sustained isometric contractions at relatively short muscle lengths.

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Roles of Reflex Activity and Co-contraction During Assessments of Spasticity of the Knee Flexor and Knee Extensor Muscles in Children With Cerebral Palsy and Different Functional Levels

Physical Therapy ◽

10.2522/ptj.20070331 ◽

2008 ◽

Vol 88 (10) ◽

pp. 1124-1134 ◽

Cited By ~ 9

Author(s):

Samuel R Pierce ◽

Mary F Barbe ◽

Ann E Barr ◽

Patricia A Shewokis ◽

Richard T Lauer

Keyword(s):

Knee Flexion ◽

Vastus Lateralis ◽

Knee Extensor ◽

Reflex Activity ◽

Knee Flexor ◽

Extensor Muscles ◽

Level I ◽

Passive Movements ◽

Knee Extensor Muscles ◽

Gmfcs Level

Background and Purpose Spasticity is a common impairment in children with cerebral palsy (CP). The purpose of this study was to examine differences in passive resistive torque, reflex activity, coactivation, and reciprocal facilitation during assessments of the spasticity of knee flexor and knee extensor muscles in children with CP and different levels of functional ability. Subjects Study participants were 20 children with CP and 10 children with typical development (TD). The 20 children with CP were equally divided into 2 groups: 10 children classified in Gross Motor Function Classification Scale (GMFCS) level I and 10 children classified in GMFCS level III. Methods One set of 10 passive movements between 25 and 90 degrees of knee flexion and one set of 10 passive movements between 90 and 25 degrees of knee flexion were completed with an isokinetic dynamometer at 15°/s, 90°/s, and 180°/s and concurrent surface electromyography of the vastus lateralis and medial hamstring muscles. Results Children in the GMFCS level III group demonstrated significantly more peak knee flexor torque with passive movements at 180°/s than children with TD. Children in the GMFCS level I and level III groups demonstrated significantly more repetitions with medial hamstring muscle activity, vastus lateralis muscle activity, and co-contraction than children with TD during the assessment of knee flexor spasticity at a velocity of 180°/s. Discussion and Conclusion Children with CP and more impaired functional mobility may demonstrate more knee flexor spasticity and reflex activity, as measured by isokinetic dynamometry, than children with TD. However, the finding of increased reflex activity with no increase in torque in the GMFCS I group in a comparison with the TD group suggests that reflex activity may play a less prominent role in spasticity.

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Relationships between contraction properties of knee extensor muscles and fasting IGF-1 and adipocytokines in physically active postmenopausal women

Clinical Physiology and Functional Imaging ◽

10.1111/j.1475-097x.2010.00950.x ◽

2010 ◽

pp. no-no

Author(s):

Toivo Jürimäe ◽

Mati Pääsuke ◽

Tatjana Kums ◽

Helena Gapeyeva ◽

Jaan Ereline ◽

...

Keyword(s):

Postmenopausal Women ◽

Knee Extensor ◽

Physically Active ◽

Extensor Muscles ◽

Knee Extensor Muscles

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Neuromuscular Differences Between Men and Prepubescent Boys During a Peak Isometric Knee Extension Intermittent Fatigue Test

Pediatric Exercise Science ◽

10.1123/pes.22.2.205 ◽

2010 ◽

Vol 22 (2) ◽

pp. 205-217 ◽

Cited By ~ 22

Author(s):

Vasilios Armatas ◽

Eleni Bassa ◽

Dimitrios Patikas ◽

Ilias Kitsas ◽

Georgios Zangelidis ◽

...

Keyword(s):

Fatigue Test ◽

Vastus Lateralis ◽

Knee Extensor ◽

Biceps Femoris ◽

Knee Extension ◽

Initial Value ◽

Antagonist Activity ◽

Extensor Muscles ◽

Isometric Knee Extension ◽

Knee Extensor Muscles

The aim of this study was to examine the fatigue and recovery in boys and men during a maximal intermittent isometric fatigue test of the knee extensor muscles, by evaluating the electromyogram of vastus lateralis, vastus medialis and biceps femoris. Thirteen boys (10.0 ± 0.8yrs) and 13 men (26.1 ± 4.2yrs) were fatigued until torque reached 50% of its initial value. Three and 6 min after, a maximal isometric knee extension test was assessed. Men had faster torque decline during fatigue and slower torque recovery compared with boys. Agonist activity declined in both groups during fatigue but men had greater extent of reduction. After 6 min boys recovered fully in respect to agonist EMG, whereas this was not the case for the men. The lower level of fatigue and faster recovery in boys could be attributed to the limited inhibition that was observed in the boys’ agonist muscles, whereas the antagonist activity does not seem to play a role in the fatigue or recovery differences between the groups.

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Impaired muscle glycogen resynthesis after eccentric exercise

Journal of Applied Physiology ◽

10.1152/jappl.1990.69.1.46 ◽

1990 ◽

Vol 69 (1) ◽

pp. 46-50 ◽

Cited By ~ 95

Author(s):

D. L. Costill ◽

D. D. Pascoe ◽

W. J. Fink ◽

R. A. Robergs ◽

S. I. Barr ◽

...

Keyword(s):

Muscle Soreness ◽

Glycogen Content ◽

Vastus Lateralis ◽

Knee Extensor ◽

Serum Creatine Kinase ◽

Eccentric Contractions ◽

O2 Uptake ◽

Maximal Extension ◽

Extensor Muscles ◽

Knee Extensor Muscles

Eight men performed 10 sets of 10 eccentric contractions of the knee extensor muscles with one leg [eccentrically exercised leg (EL)]. The weight used for this exercise was 120% of the maximal extension strength. After 30 min of rest the subjects performed two-legged cycling [concentrically exercised leg (CL)] at 74% of maximal O2 uptake for 1 h. In the 3 days after this exercise four subjects consumed diets containing 4.25 g CHO/kg body wt, and the remainder were fed 8.5 g CHO/kg. All subjects experienced severe muscle soreness and edema in the quadriceps muscles of the eccentrically exercised leg. Mean (+/- SE) resting serum creatine kinase increased from a preexercise level of 57 +/- 3 to 6,988 +/- 1,913 U/l on the 3rd day of recovery. The glycogen content (mmol/kg dry wt) in the vastus lateralis of CL muscles averaged 90, 395, and 592 mmol/kg dry wt at 0, 24, and 72 h of recovery. The EL muscle, on the other hand, averaged 168, 329, and 435 mmol/kg dry wt at these same intervals. Subjects receiving 8.5 g CHO/kg stored significantly more glycogen than those who were fed 4.3 g CHO/kg. In both groups, however, significantly less glycogen was stored in the EL than in the CL.

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Differential serial sarcomere number adaptations in knee extensor muscles of rats is contraction type dependent

Journal of Applied Physiology ◽

10.1152/japplphysiol.00481.2005 ◽

2005 ◽

Vol 99 (4) ◽

pp. 1352-1358 ◽

Cited By ~ 71

Author(s):

Timothy A. Butterfield ◽

Timothy R. Leonard ◽

Walter Herzog

Keyword(s):

Vastus Lateralis ◽

Unit Length ◽

Knee Extensor ◽

Repeated Bout Effect ◽

Extensor Muscles ◽

In Series ◽

Downhill Walking ◽

Repeated Bout ◽

Knee Extensor Muscles ◽

Sarcomere Number

Sarcomerogenesis, or the addition of sarcomeres in series within a fiber, has a profound impact on the performance of a muscle by increasing its contractile velocity and power. Sarcomerogenesis may provide a beneficial adaptation to prevent injury when a muscle consistently works at long lengths, accounting for the repeated-bout effect. The association between eccentric exercise, sarcomerogenesis and the repeated-bout effect has been proposed to depend on damage, where regeneration allows sarcomeres to work at shorter lengths for a given muscle-tendon unit length. To gain additional insight into this phenomenon, we measured fiber dynamics directly in the vastus lateralis (VL) muscle of rats during uphill and downhill walking, and we measured serial sarcomere number in the VL and vastus intermedius (VI) after chronic training on either a decline or incline grade. We found that the knee extensor muscles of uphill walking rats undergo repeated active concentric contractions, and therefore they suffer no contraction-induced injury. Conversely, the knee extensor muscles during downhill walking undergo repeated active eccentric contractions. Serial sarcomere numbers change differently for the uphill and downhill exercise groups, and for the VL and VI muscles. Short muscle lengths for uphill concentric-biased contractions result in a loss of serial sarcomeres, and long muscle lengths for downhill eccentric-biased contractions result in a gain of serial sarcomeres.

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