Changes In Maximal Isometric Strength Research Articles

Changes in Maximal Isometric Quadriceps Strength after the Application of Ultrasound-Guided Percutaneous Neuromodulation of the Femoral Nerve: A Case Series

Abstract Introduction For those individuals who have suffered an injury to the knee or undergone a surgical intervention, the early recovery of the muscle strength contraction properties of the quadriceps is essential for a favorable recovery and for a return to the activities of daily living and other work- or sports-related activities. Objectives To evaluate the changes in maximal isometric strength (MIS) of the quadriceps muscle after the application of ultrasound-guided percutaneous neuromodulation (US-guided PNM) on the femoral nerve. Materials and Methods A case series involving subjects who had previously presented unilateral knee pathology and were in the stage of recovery of quadriceps strength. The subjects were pain-free at the time of the dynamometry measurements, which were performed before and after the application of the US-guided PNM technique. The isometric measurement was performed using the KINEO dynamometry system, performing a preintervention measurement of the mean maximal isometric strength (mMIS) based on 3 repetitions (3 seconds contraction and 6 seconds relaxation). The US-guided PNM technique was performed on the femoral nerve, using the Physio Invasiva CE0120 device (Prim Physio, Madrid, Spain) and a GE Logiq e R7 ultrasound (GE Healthcare, Chicago, IL, USA). Results In total, 13 subjects participated in the present study. Significant changes were obtained (p < 0.001) in the mMIS of the quadriceps of the affected knee, which progressed from a mean strength of 25.91 kg (standard deviation [SD]: 7.17 kg) to a mean strength of 29.98 kg (SD: 9.06 kg). Discussion In subjects with knee pathology, the quadriceps muscle is inhibited despite being pain-free during the strength measurements. This process of inhibition can improve with the application of low frequency percutaneous electrical stimulation on the femoral nerve. This technique represents a complementary strategy for the recovery of the normal strength values in pathological knees with or without prior surgery. Conclusions Ultrasound-guided PNM is an effective technique for the reestablishment of quadriceps strength in inhibited muscles.

Serial assessment of local peripheral vascular function after eccentric exercise

Muscle damage is a common response to unaccustomed eccentric exercise; however, the effects of skeletal muscle damage on local vascular function and blood flow are poorly understood. This study examined serial local vascular responses to flow-mediated (endothelial-dependent) and nitroglycerin-mediated (endothelial-independent) dilation in the brachial artery after strenuous eccentric exercise and serially assessed resting blood flow. Ten healthy males performed 50 maximal eccentric unilateral arm contractions to induce muscle damage to the biceps brachii. Changes in maximal isometric strength and vascular responses were assessed 1, 24, 48, and 96 h after exercise. Mean blood velocities and arterial diameters, measured with Doppler ultrasound, were used to calculate blood flow and shear stress (expressed as area under the curve). Eccentric exercise resulted in impaired maximal isometric strength for up to 96 h (p < 0.001). Reductions in flow-mediated dilation (before exercise, 9.4% ± 2.6%; 1 h after exercise, 5.1% ± 2.2%) and nitroglycerin responses (before exercise, 26.3% ± 6.5%; 1 h after exercise, 20.7% ± 4.7%) were observed in the 1 h after exercise and remained lower for 96 h (p < 0.05). The shear stress response was attenuated immediately after exercise and remained impaired for 48 h (p < 0.05). Resting blood pressure and muscle blood flow remained similar throughout the study. Results suggest that muscle damage from eccentric exercise leads to impaired local endothelial and vascular smooth muscle function. Lower shear stress after exercise might contribute to the observed reduction in flow-mediated dilation responses, but the mechanism responsible for the attenuated endothelial-independent vasodilation remains unclear.

Effect of Slow-Velocity Lengthening Contractions on Muscle Damage Induced by Fast-Velocity Lengthening Contractions

This study tested the hypothesis that the first exercise bout consisting of slow-velocity (30° · s(-1)) maximal lengthening contractions would not affect muscle damage in a subsequent bout consisting of fast-velocity (210° · s(-1)) lengthening contractions. Eighteen men were randomly assigned into either a repeated bout group (n = 10) or control group (n = 8). The repeated bout group performed 2 bouts of exercise consisting of 210 maximal lengthening contractions of the elbow flexors separated by 14 days at a velocity of 30° · s(-1) for the first and 210° · s(-1) for the second bout. The control group performed a single bout of the fast-velocity exercise. Changes in maximal isometric strength, range of motion (ROM), upper-arm circumference, muscle thickness, muscle soreness, serum creatine kinase, and lactate dehydrogenase activities were measured before, immediately after, and 24 to 96 hours after exercise. The repeated bout group showed significantly (p < 0.05) smaller changes in all criterion measures except for muscle soreness after the fast-velocity exercise compared with the control group. A significant (p < 0.05) difference was evident only for ROM between the slow- and fast-velocity bouts of the repeated bout group. These results suggest that slow-velocity exercise reduced muscle damage induced by fast-velocity exercise, although the reduction was not large.

Responses of old men to repeated bouts of eccentric exercise of the elbow flexors in comparison with young men

A bout of eccentric exercise confers protection against subsequent bouts of the same exercise. This study investigated whether the protective effect would be produced similarly between old and young adults. Eight old men (70.5 +/- 4.1 years) and ten young men (20.4 +/- 2.0 years) performed two bouts of eccentric exercise of the elbow flexors (six sets of five eccentric actions) separated by 4 weeks. Changes in maximal isometric strength, range of motion (ROM), upper arm circumference (CIR), plasma creatine kinase (CK) activity, myoglobin (Mb) concentration, and muscle soreness (SOR) before, immediately after, and 1, 24, 48, 72 and 96 h following exercise were compared between bouts, and between groups by a two-way repeated measures ANOVA. Changes in the measures following the first bout were significantly (P < 0.05) smaller for the old than the young group. The young group showed significantly (P < 0.05) smaller changes in all measures following the second bout than the first bout; however, the old group had the protective effect only for ROM, Mb, and SOR. The magnitude of the effect observed for ROM and Mb concentration in the old group was significantly (P < 0.05) smaller compared with that of the young group. These results suggest that the protective effect conferred by the first bout was less for the old than the young group. This may be due to the less muscle damage after the first bout in the old subjects, but it is also possible that the protective effect of old adults does not last as long as that of young adults.

Effects of number of eccentric muscle actions on first and second bouts of eccentric exercise of the elbow flexors

This study compared changes in indirect markers of muscle damage following eccentric exercise of the elbow flexors among the exercises consisting of different number of eccentric actions. Sixty male athletes were placed into one of the six groups (n=10 per group) based on the number of eccentric actions for the first (ECC1) and second exercise bouts (ECC2). Single bout groups (30, 50, and 70) performed ECC1 only, and repeated bout groups (30-30, 50-50, and 70-70) performed ECC2 3 days after ECC1. Another 10 male athletes performed different number of eccentric actions for ECC1 (30) and ECC2 (70) separated by 3 days (30-70). Changes in maximal isometric strength (MVC), range of motion (ROM), upper arm circumference (CIR), serum creatine kinase activity, myoglobin, and nitric oxide concentrations and muscle soreness for 10 days following ECC1 were compared among groups by two-way repeated measures ANOVA. Changes in MVC, ROM, and CIR following ECC1 were significantly (P<0.05) smaller for the groups that performed 30 eccentric actions compared with other groups. No significant differences between 30 and 30-30, 50 and 50-50, and 70 and 70-70 were evident for the changes in the measures for 10 days following ECC1 except for the acute decreases in MVC and ROM immediately after ECC2 for the repeated bout groups. The 30-30 and 30-70 groups showed similar changes in all criterion measures. It is concluded that recovery from eccentric exercise is not retarded by the second bout of eccentric exercise regardless of the number of eccentric actions.

Partial Protection against Muscle Damage by Eccentric Actions at Short Muscle Lengths

This study investigated the hypothesis that maximal eccentric actions at a short muscle length would fail to confer a protective effect against muscle damage induced by maximal eccentric exercise at a long muscle length. Eleven males performed 24 maximal eccentric actions of the nondominant elbow flexors over a short extension range from an elbow joint angle of 0.87-1.74 rad (S-ECC) followed 4 wk later by eccentric actions at a long range of 2.27-3.14 rad (L-ECC). A second group of 11 males performed L-ECC on two occasions using the nondominant arm separated by 4 wk. Changes in maximal isometric strength, range of motion, upper arm circumference, muscle soreness, plasma creatine kinase and aspartate aminotransferase activities, and B-mode ultrasound images were compared between bouts and between groups by two-way repeated measures ANOVA. All measures changed significantly (P < 0.01) after the first bout; however, the effects were significantly (P < 0.01) smaller after S-ECC compared with L-ECC. The second bout resulted in significantly (P < 0.01) reduced changes in all measures compared with the first bout in the subjects who performed L-ECC on both occasions. The subjects who performed S-ECC in the first bout displayed significantly smaller changes after L-ECC than those seen after L-ECC alone, with the degree of attenuation being around 50-70%. Contrary to the hypothesis, S-ECC provided partial but effective protection against L-ECC. This result suggests adaptations associated with the repeated bout effect were also produced after S-ECC, but the degree of adaptations was not as strong as that by L-ECC. Eccentric exercise at a short extension range can be used as a strategy to present severe muscle damage.

Reproducibility of maximal quadriceps strength and its relationship to maximal voluntary activation in postpoliomyelitis syndrome

Horemans HL, Beelen A, Nollet F, Jones DA, Lankhorst GJ. Reproducibility of maximal quadriceps strength and its relationship to maximal voluntary activation in postpoliomyelitis syndrome. Arch Phys Med Rehabil 2004;85:1273–8. Objectives To determine what changes in maximal isometric strength can be detected in a symptomatic quadriceps muscle in patients with postpoliomyelitis syndrome (PPS) and to investigate the association between the variability in maximal strength and maximal voluntary activation (MVA). Design Repeated-measures over a 3-week interval. Setting University hospital. Patients Convenience sample of 65 patients with PPS. Intervention Dynamometer testing. Main outcome measures Maximal voluntary contraction (MVC) torque of the quadriceps was measured with a Kin-Com dynamometer and MVA was determined by twitch interpolation. Results The mean difference between the 2 consecutive measurements was −0.7±12.8Nm (95% confidence interval [CI], −3.9 to 2.5). The test-retest reliability was excellent for MVC torque (intraclass correlation coefficient [ICC]=.96; 95% CI, .93–.98) and moderate for MVA (ICC=.73; 95% CI, .56–.85). The smallest detectable change in MVC torque was 25% for an individual. The variability in MVA explained 18% of the variability in maximal strength. Conclusions Variability in maximal quadriceps strength, measured with a fixed dynamometer, was large and partly related to variability in MVA. This implies that even with optimally standardized strength testing, a follow-up of many years is required to objectify progression of quadriceps weakness in an individual patient with PPS. To demonstrate changes in strength in groups of patients in follow-up or intervention studies, feasible sample sizes are required.

Physical activity and the changes in maximal isometric strength in men and women from the age of 75 to 80 years.

To research the natural changes in maximal isometric strength, over a period of 5 years, in men and women aged 75 at baseline, and to study the effect of everyday physical activity on strength alterations. A 5-year longitudinal study. Exercise laboratory. The target group in 1989 was the total 75-year-old population of Jyväskylä. One hundred one men (81%) and 186 women (75%) participated in baseline strength tests, and after 5 years, 55 men and 111 women (70% and 72% of the survivors) took part in the follow-up measurements. Maximal isometric hand grip, arm flexion, knee extension, trunk flexion, and trunk extension forces were measured using dynamometers. Self-rated physical activity was recorded using a scale by Grimby (1986). Strength changes were compared between groups based on the amount of everyday physical activity: (1) remained active (AA, 24 men, 24 women); (2) remained sedentary (SS, 11 men, 43 women); (3) decreased activity (AS, 11 women); and (4) increased activity (SA, 32 women). AS and SA could be formed for women only because of the small number of men. All analyses were stratified by gender. The average percentage change in strength over 5 years among survivors varied from a 4% increase in knee extension strength observed in men and women to a 16% decrease in grip strength in women. The grip strength decrease was greater in women than men. The AA men maintained their trunk extension strength at a higher level than the SS men. Time by group interactions in men were not significant. In women, the rate of decline in AS was 32% in grip and 27% in elbow flexion strength, which was greater than in the other activity groups. The AA women retained their knee extension strength at a higher level than the other groups. Those who died before follow-up tests exhibited poorer strength test results at baseline. Physical activity decreased over follow-up. Strength alterations with age differed between muscle groups. Undertaking everyday physical activities such as household work, walking, and gardening, which are also the most common physically demanding activities of older people, may play an important role in maintaining strength at an adequate level for independent living.