Older adults are less steady during submaximal isometric contractions with the knee extensor muscles

2002 ◽  
Vol 92 (3) ◽  
pp. 1004-1012 ◽  
Author(s):  
Brian L. Tracy ◽  
Roger M. Enoka
Keyword(s):  
Maximum Voluntary Contraction ◽  
Knee Extensor ◽  
Voluntary Contraction ◽  
Eccentric Contractions ◽  
Isometric Contractions ◽  
Antagonist Muscle ◽  
Old Adults ◽  
Extensor Muscles ◽  
Young Subjects ◽  
Knee Extensor Muscles

This study compared the steadiness of submaximal contractions with the knee extensor muscles in young and old adults. Twenty young and twenty old subjects underwent assessment of isometric maximum voluntary contraction (MVC), one-repetition maximum (1-RM) strength, and steadiness during isometric, concentric, and eccentric contractions with the knee extensor muscles. The old adults displayed 33% lower MVC force and a 41% lower 1-RM load. The coefficient of variation for force was significantly greater for the old adults during isometric contractions at 2, 5, and 10% of MVC but not at 50% MVC. The decline in steadiness at low forces experienced by the men was marginally greater than that experienced by the women. The steadiness of concentric and eccentric contractions was similar in young and old adults at 5, 10, and 50% of 1-RM load. Old subjects exhibited greater coactivation of an antagonist muscle compared with young subjects during the submaximal isometric and anisometric contractions. These results indicate that, whereas the ability to exert steady submaximal forces with the knee extensor muscles was reduced in old adults, fluctuations in knee joint angle during slow movements were similar for young and old adults.

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

2003 ◽  
Vol 95 (4) ◽  
pp. 1515-1522 ◽  
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).

Exercise-induced muscle injury augments forearm vascular resistance during leg exercise

1998 ◽  
Vol 275 (2) ◽  
pp. H443-H447 ◽  
Author(s):  
Chester A. Ray ◽  
Edward T. Mahoney ◽  
Keith M. Hume
Keyword(s):  
Vascular Resistance ◽  
Muscle Injury ◽  
Forearm Blood Flow ◽  
Maximum Voluntary Contraction ◽  
Knee Extensor ◽  
Voluntary Contraction ◽  
Extensor Muscles ◽  
Exercise Induced ◽  
Knee Extensor Muscles ◽  
Forearm Vascular Resistance

The purpose of the present investigation was to examine the effect of exercise-induced muscle injury on hemodynamic responses during exercise. Ten subjects performed unilateral isometric knee extensions (IKE) at 30% of preinjury maximum voluntary contraction to fatigue and for 3 min before and 48 h after muscle injury. Muscle injury was elicited by performing 8 sets of 10 repetitions of eccentric muscle actions of the knee extensor muscles (i.e., quadriceps muscles) by lowering a weight equivalent to 75% of eccentric maximum load. Exercise time to fatigue for IKE at 30% of maximum voluntary contraction in the injured leg was significantly decreased from preinjury to postinjury IKE (257 ± 21 to 203 ± 23 s; n = 10), but was unchanged in the control leg (244 ± 16 to 254 ± 20 s; n = 7). With the use of a 10-cm visual analog scale, ratings of muscle soreness in the injured leg increased from 0 to 5.1 ± 0.7 cm ( P < 0.001) but were not changed in the control leg (0 both times). Both heart rate and mean arterial pressure responses to exercise were unchanged following muscle injury. Forearm blood flow and forearm vascular resistance were not different at rest and during the first minute of exercise before and after muscle injury. However, after muscle injury, forearm blood flow was significantly lower and forearm vascular resistance was significantly higher ( P < 0.03) during the second and third minutes of exercise. There were no significant changes in any variables with the contralateral control leg. In four subjects, resting magnetic resonance images demonstrated a 23% greater relative cross-sectional area of the knee extensor muscles with an elevated transverse relaxation time in the injured versus control leg. The results indicate that forearm vascular resistance is augmented during isometric knee extension following muscle injury of the knee extensor muscles. The data suggest that muscle injury alters vascular control to non-exercising skeletal muscle during exercise.

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

2005 ◽  
Vol 99 (2) ◽  
pp. 579-586 ◽  
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.

Age and contraction type influence motor output variability in rapid discrete tasks

2002 ◽  
Vol 93 (2) ◽  
pp. 489-498 ◽  
Author(s):  
Evangelos A. Christou ◽  
Les G. Carlton
Keyword(s):  
Standard Deviation ◽  
Knee Flexion ◽  
Maximum Voluntary Contraction ◽  
Voluntary Contraction ◽  
Peak Force ◽  
Full Extension ◽  
Old Adults ◽  
Time To Peak ◽  
Impulse Duration ◽  
Young Subjects

The purpose of this study was to examine the ability to control knee-extension force during discrete isometric (IC), concentric (CC), and eccentric contractions (EC) in 24 young (mean age ± SD = 25.3 ± 2.8 yr) and 24 old (mean age ± SD = 73.3 ± 5.5 yr) healthy and active individuals. Subjects were to match a parabola with a time to peak force of 200 ms during IC, CC, and EC at six target levels of force [20, 35, 50, 65, 80, and 90% of the maximum voluntary contraction (MVC)]. ICs were performed at 90° of knee flexion, whereas CCs and ECs ranged from 90 to 80° of knee flexion (0° is full extension) at a slow velocity (25°/s). Results showed that subjects produced similar MVC forces for the three types of contractions. Young subjects produced greater MVC forces than old subjects, and within each age group, men produced greater force than women. The variability (standard deviation) of peak force and impulse in absolute values was greater for young compared with old subjects. When variability was normalized to the force produced [coefficient of variation (CV)], however, old subjects exhibited greater CV than young subjects for peak force and impulse. Both the standard deviation and CV of time to peak force and impulse duration were greater for the old adults. In general, ECs were more variable than ICs and CCs, and old adults exhibited greater CV compared with young adults during rapid, discrete ICs, CCs, and particularly ECs of the quadriceps.

Sex differences in neuromuscular function after repeated eccentric contractions of the knee extensor muscles

2017 ◽  
Vol 117 (6) ◽  
pp. 1119-1130 ◽  
Author(s):  
Andrea Lee ◽  
Jake Baxter ◽  
Claire Eischer ◽  
Matt Gage ◽  
Sandra Hunter ◽  
...  
Keyword(s):  
Sex Differences ◽  
Knee Extensor ◽  
Neuromuscular Function ◽  
Eccentric Contractions ◽  
Extensor Muscles ◽  
Knee Extensor Muscles

Impaired muscle glycogen resynthesis after eccentric exercise

1990 ◽  
Vol 69 (1) ◽  
pp. 46-50 ◽  
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.

scholarly journals Characterizing rapid-onset vasodilation to single muscle contractions in the human leg

2015 ◽  
Vol 118 (4) ◽  
pp. 455-464 ◽  
Author(s):  
Daniel P. Credeur ◽  
Seth W. Holwerda ◽  
Robert M. Restaino ◽  
Phillip M. King ◽  
Kiera L. Crutcher ◽  
...  
Keyword(s):  
Maximum Voluntary Contraction ◽  
Knee Extensor ◽  
Rapid Onset ◽  
Knee Extension ◽  
Voluntary Contraction ◽  
Muscle Contractions ◽  
Isometric Contractions ◽  
Single Muscle ◽  
Isometric Knee Extension ◽  
Mechanical Factors

Rapid-onset vasodilation (ROV) following single muscle contractions has been examined in the forearm of humans, but has not yet been characterized in the leg. Given known vascular differences between the arm and leg, we sought to characterize ROV following single muscle contractions in the leg. Sixteen healthy men performed random ordered single contractions at 5, 10, 20, 40, and 60% of their maximum voluntary contraction (MVC) using isometric knee extension made with the leg above and below heart level, and these were compared with single isometric contractions of the forearm (handgrip). Single thigh cuff compressions (300 mmHg) were utilized to estimate the mechanical contribution to leg ROV. Continuous blood flow was determined by duplex-Doppler ultrasound and blood pressure via finger photoplethysmography (Finometer). Single isometric knee extensor contractions produced intensity-dependent increases in peak leg vascular conductance that were significantly greater than the forearm in both the above- and below-heart level positions (e.g., above heart level: leg 20% MVC, +138 ± 28% vs. arm 20% MVC, +89 ± 17%; P < 0.05). Thigh cuff compressions also produced a significant hyperemic response, but these were brief and smaller in magnitude compared with single isometric contractions in the leg. Collectively, these data demonstrate the presence of a rapid and robust vasodilation to single muscle contractions in the leg that is largely independent of mechanical factors, thus establishing the leg as a viable model to study ROV in humans.

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