Effects of velocity on upper to lower extremity muscular work and power output ratios of intercollegiate athletes

Bar Load-Velocity Profile of Full Squat and Bench Press Exercises in Young Recreational Athletes

The purpose of this study was to determine the mean propulsive velocity (MVP) at various percentages of one repetition maximum (1RM) in the full squat and chest press exercises. A total of 96 young women and 256 young men (recreational athletes) performed an incremental test (50−60−70−80% 1RM) comprising the bench press and full squat exercises in two different sessions. The individual load and velocity ratios were established through the MPV. Data were analyzed using SPSS software version 25.0, with the significance level set at 5%. The following findings were revealed: highly linear load-velocity relationships in the group of women (r = 0.806 in the squat, and r = 0.872 in the bench press) and in the group of men (r = 0.832 and r = 0.880, respectively); significant differences (p < 0.001) in the MPV at 50−70−80% 1RM between the bench press and the full squat in men and at 70−80% 1RM in women; and a high variability in the MPV (11.49% to 22.63) in the bench press and full squat (11.58% to 25.15%) was observed in women and men (11.31% to 21.06%, and 9.26% to 24.2%) at the different percentages of 1RM evaluated. These results suggest that the load-velocity ratio in non-strength-trained subjects should be determined individually to more precisely establish the relative load to be used in a full squat and bench press training program.

Interseason variability in isokinetic strength and poor correlation with Nordic hamstring eccentric strength in football players

In elite sport, the use of strength testing to establish muscle function and performance is common. Traditionally, isokinetic strength tests have been used, measuring torque during concentric and eccentric muscle action. A device that measures eccentric hamstring muscle strength while performing the Nordic hamstring exercise is now also frequently used. The study aimed to investigate the variability of isokinetic muscle strength over time, for example, between seasons, and the relationship between isokinetic testing and the new Nordic hamstring exercise device. All teams (n = 18) eligible to compete in the premier football league in Qatar underwent a comprehensive strength assessment during their periodic health evaluation at Aspetar Orthopaedic and Sports Medicine Hospital in Qatar. Isokinetic strength was investigated for measurement error, and correlated to Nordic hamstring exercise strength. Of the 529 players included, 288 players had repeated tests with 1/2 seasons between test occasions. Variability (measurement error) between test occasions was substantial, as demonstrated by the measurement error (approximately 25 Nm, 15%), whether separated by 1 or 2 seasons. Considering hamstring injuries, the same pattern was observed among injured (n = 60) and uninjured (n = 228) players. A poor correlation (r = .35) was observed between peak isokinetic hamstring eccentric torque and Nordic hamstring exercise peak force. The strength imbalance between limbs calculated for both test modes was not correlated (r = .037). There is substantial intraindividual variability in all isokinetic test measures, whether separated by 1 or 2 seasons, irrespective of injury. Also, eccentric hamstring strength and limb-to-limb imbalance were poorly correlated between the isokinetic and Nordic hamstring exercise tests.

Work and power reduced in L-dopa naïve patients in the early-stages of Parkinson’s disease

ABSTRACT Studies which have investigated muscular performance during the initial stages of Parkinson´s disease (PD) without L-dopa treatments were not found. Objective to assess whether muscular performance, work and power, of the trunk and lower limbs in L-dopa naïve patients in the early stages of PD was lower than those of healthy subjects and to compare muscular performance between the lower limbs. Method Ten subjects with PD, Hoehn and Yahr (HY) I-II, L-dopa naïve and 10 subjects in the control group were assessed with the isokinetic dynamometer. Results ANOVAs revealed that work and power measures of the trunk, hip, knee, and ankle muscular groups were lower in PD compared with the control group (p < 0.05). There were no significant differences in muscular performance between the lower limbs. Conclusion The results suggested the use of specific exercises, as rehabilitation strategies, to improve the ability to produce work and power with this population.

Similar increases in muscle size and strength in young men after training with maximal shortening or lengthening contractions when matched for total work

Training exclusively with eccentric (lengthening) contractions can result in greater muscular adaptations than training with concentric (shortening) contractions. We aimed to determine whether training-induced increases in muscle size and strength differed between muscles performing maximal lengthening (LC) or maximal shortening (SC) contractions when total external work is equivalent. Nine healthy young males completed a 9-week isokinetic (0.79 rad/s) resistance training program of the elbow flexors whereby they performed LC with one arm and an equivalent volume of total external work with the contralateral arm as SC. Training increased isometric peak torque for both LC (~10%) and SC (~20%) with no difference (P = 0.14) between conditions. There were also similar increases in isokinetic peak torque at both slow (0.79 rad/s) and fast (5.24 rad/s) shortening and lengthening peak torque for both LC (~8-10%) and SC (~9-20%). Training increased work per repetition similarly for both LC (~17%) and SC (~22%), in spite of ~40% greater work per repetition with LC. The increase in muscle cross-sectional area with training was also similar (P = 0.37) between LC (~6.5%) and SC (~4.6%). We conclude that increases in muscle size and strength with short-term unilateral resistance training are unrelated to muscle contraction type when matched for both exercise intensity (i.e. maximal contractions) and total external work.

Child-adult differences in muscle strength and activation pattern during isometric elbow flexion and extension

Muscle strength and activation were compared in boys and men during maximal voluntary elbow flexion and extension contractions. Peak torque, peak rate of torque development (d/dmax), rate of muscle activation, and electromechanical delay (EMD) were measured in 15 boys (aged 9.7 +/- 1.6 years) and 16 men (aged 22.1 +/- 2.8 years). During flexion, peak torque was significantly lower in boys than in men (19.5 +/- 5.8 vs. 68.5 +/- 11.0 Nm, respectively; p < 0.05), even when controlling for upper-arm cross-sectional area (CSA), and peak electromyography activity. Boys also exhibited a lower normalized d/dmax (7.2 +/- 1.7 vs. 9.5 +/- 1.6 (Nm.s-1).(Nm-1), respectively; p < 0.05) and a significantly longer EMD (75.5 +/- 28.4 vs. 47.6 +/- 17.5 ms, respectively). The pattern was similar for extension, except that group differences in peak torque were no longer significant when normalized for CSA. These results suggest that children may be less able to recruit or fully utilize their higher-threshold motor units, resulting in lower dimensionally normalized maximal torque and rate of torque development.

Analysis of impairments influencing gait velocity and asymmetry of hemiplegic patients after mild to moderate stroke

OBJECTIVE

To identify the most important impairments determining gait velocity and asymmetry in patients with mild to moderate stroke.

DESIGN

Descriptive analysis of convenience sample.

SETTING

Outpatient rehabilitation clinic of a hospital in Taiwan.

PARTICIPANTS

Twenty-six subjects with mild to moderate spastic hemiparesis after a single onset of stroke, all able to walk independently without any assistance or device.

INTERVENTIONS

Not applicable.

MAIN OUTCOME MEASURES

Subjects' maximal muscle strength (isokinetic peak torque, total work), motor and sensation function, and ankle plantarflexor spasticity of the affected lower extremity were examined using the Cybex 6000 dynamometry, Fugl-Meyer Assessment, and Modified Ashworth Scale, respectively. Gait velocity, as well as temporal and spatial asymmetry, were evaluated when subjects walked at their comfortable and fast speeds by using the GaitMatII.

RESULTS

Regression analyses revealed that the total work isokinetic measures of the affected hip flexors and knee extensors were the most important independent determinants of the comfortable and fast gait velocities, respectively (R(2)=.57, R(2)=.72). Spasticity of the affected plantarflexors was the most important independent determinant of temporal and spatial gait asymmetry during comfortable-speed (R(2)=.76 for temporal asymmetry; R(2)=.46 for spatial asymmetry) and fast-speed (R(2)=.75 for temporal asymmetry; R(2)=.45 for spatial asymmetry) walking.

CONCLUSIONS

Gait velocity and asymmetry of patients with mild to moderate stroke were affected by different physical impairments. Whereas gait velocity was mainly affected by weakness of the affected hip flexors and knee extensors, gait asymmetry was influenced primarily by the degree of the spasticity of the affected ankle plantarflexors. Therapeutic interventions aiming to improve different aspects of gait performance of these patients may emphasize treatment of different impairments.

Isokinetic muscle performance in major depressive disorder: alterations by antidepressant therapy

The aims of this study were (i) to examine whether patients with major depressive disorder (MDD) differ from healthy control subjects with respect to isokinetic muscle performance (IMP) as measured by a dynamometer; (ii) to investigate the effect of subchronic treatment on the IMP in depressed patients. Thirty-eight patients with MDD, and 41 sex- and age-matched healthy controls participated in this study. The severity of depression and anxiety levels were evaluated by the Hamilton Depression and Anxiety Scales. Quadriceps and hamstring IMPs were determined by using an isokinetic dynamometer before and after subchronic antidepressant treatment. The patients had lower IMP levels than healthy controls. After treatment for three months with selective serotonin reuptake inhibitors, the IMP levels increased significantly. These findings suggest that (i) MDD may be characterized by reduced IMP levels; and (ii) treatment with antidepressants may increase the IMP levels, as a state marker for depression. It was concluded that (i) isokinetic muscle performance may be used as a state marker for monitoring antidepressant drug effects on MDD; (ii) isokinetic exercise increasing IMP may be used in the treatment of depression.

Isokinetic muscle performance in major depressive disorder: alterations by antidepressant therapy

The aims of this study were (i) to examine whether patients with major depressive disorder (MDD) differ from healthy control subjects with respect to isokinetic muscle performance (IMP) as measured by a dynamometer; (ii) to investigate the effect of subchronic treatment on the IMP in depressed patients. Thirty-eight patients with MDD, and 41 sex- and age-matched healthy controls participated in this study. The severity of depression and anxiety levels was evaluated by the Hamilton Depression and Anxiety Scales. Quadriceps and hamstring IMPs were determined by using an isokinetic dynamometer before and after subchronic antidepressant treatment. The patients had lower IMP levels than healthy controls. After treatment for three months with selective serotonin reuptake inhibitors, the IMP levels increased significantly. These findings suggest that (i) MDD may be characterized by reduced IMP levels; and (ii) treatment with antidepressants may increase the IMP levels, being a state marker for depression. It was concluded that (i) isokinetic muscle performance may be used as a state marker for monitoring antidepressant drug effects on MDD; (ii) isokinetic exercise increasing IMP may be used in the treatment of depression.