Title: The effect of alcohol drinking on the isokinetic knee strength Objectives: The objective of this thesis is to assess the effect of alcohol on isokinetic knee strength during extension and flexion. Methods: Fifteen volunteers participated in this study. Their age was 23,9 ± 1,9 years, height 179,5 ± 7,2cm and weight 78,5 ± 7,95kg. They were all students from sports faculty. One group of volunteers was given alcohol with juice (0,8g of alcohol to 1kg of fat-free mass), the second group drank only juice. We used the switch design study. We measured isokinetic knee strenght on dynamometer Cybex Humac Norm (Cybex NORM ®, Humac, CA, USA) in three types of angular velocity (6Oř/s, 180ř/s, 240ř/s). The parametrs were peak torque, muscular work, average muscular power and time to peak. Results: We registered statistically significant increase of peak torque, muscular work and average muscular powers when measuring flexion in all the three angular velocities (60ř/s, 180ř/s, 240ř/s). We did not register statistically or effect size significant diference readings of time needed for maximal peak torque when measuring flexion and extension. The only exception was angular speed 240ř/s where we registered a factually significant change in time needed for extensors to reach the maximal peak torque....

The goals of the pelvis include maintaining the center of mass of the body, assisting in foot clearance and absorb forces from the lower extremities using muscles and ligaments to stabilize the joint. A better understanding of the influence of muscle strength on controlling pelvic obliquity in a healthy population will help in understanding low back pain and overuse lower extremity injuries. Thirteen females (22 ±2 yrs) participated in isokinetic strength testing of the hip abductors, adductors, internal rotators and external rotators on a Biodex dynamometer. The subjects also underwent gait analysis during self selected pace walking and stair descent. For each muscle group subjects were divided into weaker and stronger groups based on the mean. Independent t-test revealed a significantly greater amount of pelvic obliquity in the stronger group for abductors, adductors, and internal rotators during stair descent. Subjects may be compensating for more pelvic obliquity with less movement of the hip, knee and ankle. During walking weaker external rotators was the only muscle group that significantly increased pelvic obliquity. Our study supports the finding of other studies that the external rotators contribute to pelvic stabilization during walking (Powers, 2003).

Acute static vibration-induced stretching enhanced muscle viscoelasticity but did not affect maximal voluntary contractions in footballers. J Strength Cond Res 28(11): 3105-3114, 2014-The aim of this study was to compare the effects of acute vibration-enhanced static stretching and/or static stretching alone on the strength and flexibility of the hamstrings and quadriceps muscles. Twenty-one male footballers participated in this study (21.9 ± 1.8 years; 75.54 ± 7.3 kg; 178.7 ± 6.5 cm). The experiment started with 5 minutes standardized warm-up followed by (a) baseline flexibility pretest (Split Test); (b) maximal voluntary flexion and extension (isokinetic strength) of the knee; (c) Treatment or Sham involving 45-second stretch with or without vibration for the hamstring and quadriceps muscle groups with 10-second rest between; and (d) posttest repeating the measures of the pretest. Each player randomly performed both trials on separate occasions. The vibration device operated at 35 Hz with 2 mm amplitude. Stretching with vibration statistically increased hamstring flexibility by 7.8% (p ≥ 0.05) when compared with stretching without vibration. No statistical differences for hamstring or quadriceps strength were noted between treatment conditions. There was no statistical correlation between flexibility and strength measurements. In conclusion, flexibility increased with vibration-enhanced static stretching; however, no change was evident in the maximal voluntary contractions of the knee flexors and extensors.

Title: The assesment of selected strength and stability parameters of an ankle plantar and dorsal flexion in slackliners. Objectives: To assess the relation between level of stability the dorsiflexion and the plantar flexion strength in slackliners. Methods: The research sample was composed of two groups - slackliners (9 person) and balanced control group (9 person) selected from physically active population. Probands were tested on the Flamingo test on the pressure plate, the test of the dorsiflexion and plantar flexion strenght on an isokinetic dynamometer. Slackliners underwent extra range of motions elements on the slackline. The level of stability was assessed by using the centre of pressure and the physical design of individual elements on the slackline. Power was assessed by using the peak torque at 30 ř and 120 ř. Results: Slackliners achieve bigger relative strength in the plantar angular velocity of rotation of 30 ř in both limbs than the control group (left: 1.51 ± 0.31 vs. 1.20 ± 0.30 Nm.kg-1 , p <0.05 , η2 = 0.21, right: 1.55 ± 0.34 vs. 1.21 ± 0.34 Nm.kg-1 , p <0.05, η2 = 0.22). The results of other parameters (postural stability, isokinetic power at the ankle angular velocity of 120 ř.s-1 and the time course of force) between the two groups did not differ significantly. Conclusion:...

Introduction: Isokinetic testing is used in rehabilitation settings on a regular basis, yet there is a lack of consistency in rest period usage among protocols. Purpose: The purpose of this study was to establish an optimal rest period that would allow reproducibility of strength during a common isokinetic strength-test. Methods: Twentyseven healthy college-aged males underwent isokinetic strength testing to determine peak torque at 60, 180 and 300 deg/sec, respectively. Work:rest ratios of 1:3, 1:8 and 1:12 were counterbalanced between sets. A 3 X 3 repeated measures ANOVA was used to analyze the data. The p < .05 level of significance was used for all tests. Results: There was no significant difference in either knee extension or knee flexion peak torque when comparing work:rest ratios. Conclusion: These findings suggest that a 1:3 work:rest ratio is sufficient during a common isokinetic strength test.

Healthcare costs for treating back pain have risen to 50 billion dollars a year in the past decade. In attempt reduce the risk of back pain; ergonomists use digital human modeling to assess the risks involved in functional tasks. However, current models are limited to analyzing the strength in static position. The overall goal of this study is to provide three-dimensional strength surfaces incorporating both static and dynamic strength for digital human models. Fifteen male and twenty-one female subjects were recruited. The study required two visits, were hip strength testing was performed in one visit and trunk strength testing was performed in the other visit. Hip strength was tested by completing flexion and extension isometric tests and isokinetic tests. Trunk flexion and extension strength was also measured by isometric and isokinetic tests. Isometric and Isokinetic tests were completed for trunk left and right rotation too. The data was analyzed using custom made MATLAB (Mathworks, Inc) programs and the three-dimensional strength surfaces were generated using SigmaPlot (SYSTAT Software, INC). The maximum peak torques were as followed: Hip flexion male 183Nm(57), hip flexion female 106 Nm (38), hip extension male 181 Nm (71), hip extension female 130 Nm (52), trunk flexion male 182 Nm (40.3), trunk flexion female 111.8 Nm (32), trunk extension male 328.5 Nm (52), trunk extension female 197.5 Nm (58), trunk right rotation male 71.6 Nm (20), trunk right rotation female 43 Nm (14), trunk left rotation male 71 Nm (24), and trunk left rotation female (43 Nm (17). Correlations were found between the hip and trunk joints, and the flexion and extension motion. Implementing this data into digital human models will provide realistic static and dynamic human strength parameters. Ultimately, this will help ergonomists predict and reduce high risk back injuries.

The purpose of this study was to display increase in eccentric hamstring strength after 10-weeks training program. Secondly, if such an increase occurred, would this strength change result in altered landing kinetics and improved jumping performance? 27 recreational female athletes assigned into experimental (n = 14) and control (n = 13) groups. Baseline measures of landing kinetics were collected using a force plate, strength data and proprioceptive measurements were evaluated using an isokinetic dynamometer and vertical jump performance were determined by a jumping mat. Results indicated that NHST group increased their eccentric hamstring strength after eccentric strength training program (week-1 = 233.6&plusmn / 27.5, week-10 = 253.8&plusmn / 28.4 Nm/kgbw / p&lt / .05). The results demonstrated that there were significant differences in landing mechanics for NHST group. PVGRF (week-1 = 6.2&plusmn / 0.9, week-5 = 5.3&plusmn / 0.9 / p&lt / .05), PAPGRF (week-1 = 1.1&plusmn / 0.2 &amp / week-10 = 0.8&plusmn / 0.3 / p&lt / .05) and APImp results demonstrated significant differences in trained group (week-1 = 78.1&plusmn / 13.6 &amp / week-10 = 67.8&plusmn / 9.2 / p&lt / .05). NHST group exhibited significant increase in vertical jumping ability (week-1 = 0.25&plusmn / 0.0 &amp / week-10 = 0.27&plusmn / 0.0 cm / p&lt / .01). This study supported the following points: 1) increases in the eccentric hamstring strength were evident after NHST program, 2) the increases in isokinetic strength were sufficient to cause alterations in landing kinetics to decrease the applied joint forces, so the NHST program would be an influential factor in decreasing the lower extremity injuries, and 3) the increase in the efficiency of force transfer at the final take off phase of jumping contributed to a higher performance in vertical jump.

Title: Strength asymmetries of female soccer players according to playing position Objectives: The aim of this diploma thesis was to characterize the unilateral and bilateral asymmetries of knee flexors and extensors in elite football players based on player positions and to define the characteristic isokinetic strength profile for each playing positions. Methods: The research group consisted of 66 female football players who play in the highest czech league. The players completed laboratory testing under the supervision of qualified experts, which took place according to the standard conditions described in the methodological part of this study. In the case of players, we examined the strength asymmetries in the flexors and extensors of the knee and compared them between the 4 basic positions in football. Results: After summing the data from all angular velocities (60ř.s-1 , 180ř.s-1 , 300ř.s-1 ) we found that 33% of our attackers had quadriceps asymmetries above 10%, which was the most of all posts. This is followed by goalkeepers with 28% and midfielders with 25%. The lowest percentage of quadriceps asymmetries was recorded in defenders 22%. Even in the case of hamstrings, we recorded the most asymmetries (> 10%) in attackers, up to 46%. For midfielders and defenders, it was the same result for...

Resistance training has shifted towards a high- vs low-load training approach. Heavier loads are suggested to maximally recruit motor units and optimize strength adaptations, whereas lower loads stimulate hypertrophy. However, a majority of the research has not used a true strength range when assessing load. Therefore, the purpose of this investigation was to examine and determine significant differences in strength, body composition, and hormonal markers over nine weeks of high- or low-load resistance training. Secondary purposes of the current investigation were to assess and quantify training load for resistance training using sEMG sensor-embedded compression shorts. 17 recreationally-trained males were randomized into two groups with training loads of 30 or 85% 1-RM. Both groups completed nine weeks of whole-body resistance training three days per week, with exercises performed as three sets to failure per movement. Measures were collected at baseline and every three weeks after, including muscle thickness, body composition, isometrics/isokinetic strength, and hormonal status (testosterone and cortisol). Predicted 1-RM testing was performed pre- and post-training. Both groups demonstrated significant hypertrophy and strength, although the 85% showed greater improvements in the predicted 1-RM and the isokinetic peak torque values. There were also significant differences between groups for muscle load and training load as measured by the wearables, indicating the technology was able to differentiate between resistance training intensities. However, there were no changes in any of the hormonal markers either in basal levels or acutely post-exercise. Overall, our results suggest a similar hypertrophy and hormone response occurs in both low- and high-load groups when training to failure, but the high-load results in greater strength improvements and higher muscle load output when measured by wearable technology.

Spinal manipulative therapy (SMT) is a therapeutic procedure employed by various healthcare practitioners for alleviating acute and chronic musculoskeletal complaints. This form of treatment is also delivered to enhance the performance and augment the rehabilitation of athletes. However, despite research findings alleging the strength-modulating effects of SMT alongside numerous professional athletes’ positive anecdotal claims concerning its results, the physiological processes to explain its effects remain largely unexplained. Therefore, the purpose of this work was to investigate the effects of SMT in a college-aged sample population with two experiments. The first study examined the effect of SMT targeting the lumbosacral region on concentric force production of the knee extensors and flexors. A randomized, controlled, single-blind crossover design was utilized with 21 subjects. Isometric and isokinetic peak torques (Nm) were recorded during maximal voluntary isometric contractions (MVIC) or maximal voluntary contractions (MVC) post-treatment of either SMT or a sham manipulation. The second study incorporated the same experimental design with 20 subjects to examine the effects of SMT on central nervous system (CNS) excitability. This was accomplished by assessing postactivation potentiation (PAP), measured with the Hoffmann Reflex (H-reflex). PAP is an enhanced neuromuscular response to prior contractile activity, and the H-reflex is the electromyographic (EMG) recording of submaximal electrical stimulation of the Ia monosynaptic reflex pathway. Subsequent to SMT and/or a plantar flexion MVIC, EMG amplitudes and isometric twitch torque generation of the gastrocnemius and soleus muscles were recorded during tibial nerve stimulations. The results of the first study indicate that SMT did not produce a significant strength-modulating effect during isometric and isokinetic contractions of neither knee extension nor flexion. Similarly, the second study revealed that SMT immediately preceding the MVIC to induce PAP did not significantly increase H-reflex EMG amplitudes of either muscle or the simultaneous isometric twitch torque generation compared to the MVIC only. These data from both investigations suggest that SMT does not enhance strength or PAP. The positive anecdotal claims of athletes who utilize SMT may be due to other factors, such as the clinical efficacy of the treatment in addressing musculoskeletal injuries or a placebo effect.