The purpose of the present study was to investigate the acute effects of local vibration on muscle performance at different durations and frequencies. Fifteen male handball players participated in the study voluntarily. University&rsquo / s Ethics Committee approved the study and the informed consent forms were filled by all participants. Different vibration durations, (10 sec, 1 min, 10 min), different frequencies (40 and 80 Hz), dominancy (dominant and non-dominant) and conditions (vibration and no-vibration) were independent variables of study. Dependent variables were maximum isometric strength measures under different situations. One way Repeated measures ANOVA, Bonferoni adjusted paired sample t-tests and Two way Repeated ANOVA was used for statistical analyses. Result of this study demonstrated that local vibration (LV) induced significantly higher muscle activity than no vibration (NV) condition. Strength improvements were obtained in quadriceps muscles of dominant and non-dominant legs for 40 Hz and 80 Hz. When 40 Hz vibration was applied to dominant leg with different durations (10 sec, 1 min, 10 min), significantly higher strength measures were found than no vibration. When 80 Hz vibration was applied to dominant leg with different durations (10 sec, 1 min, 10 min), only 10-sec vibration duration revealed significant increase in strength measures. When 40 Hz vibration was applied to non-dominant leg with different durations, (10 sec, 1 min, 10 min) significantly higher strength measures were found than no vibration. When 80 Hz vibration was applied to non-dominant leg with different durations (10 sec, 1 min, 10 min), 10-sec and 1 min vibration durations revealed significant increase in strength measures. However, no significant difference was obtained when the different vibration durations were compared between 40 Hz and 80 Hz.

The thesis aimed to analyse the acute neuromuscular (NM) response during and following maximum strength and power training methods. The primary aim of study one was to establish the reliability of biomechanical and surface electromyographic (sEMG) measurements during barbell squat exercise. This would enable the subsequent studies to precisely assess muscle activity and mechanical power during barbell resistance exercise sessions. Nine male well-trained subjects performed squat exercise on three separate trial days. Each trial comprised one set of squat at 50, 75 and 100% of 3RM load. Synchronous recordings of knee joint kinematics from a flexible electrogoniometer, barbell displacement from a single linear position transducer and quadriceps sEMG amplitude were made. The mean maximum knee angle during squat was recorded at each load, and the overall inter-trial coefficient of variation (CV) was 5.5%. Mean concentric repetition power was processed from displacement data and derived into force and velocity values. The overall inter-trial CV for mean power was found to be 8.4%. The raw sEMG signal was processed into root mean square (RMS) amplitude and normalised to values taken from pre-trial knee extension maximum voluntary contractions (MVC). RMS amplitude was processed for the whole concentric phase and a 200 ms time interval at a knee angle of 70°, which matched the knee angle used during MVC. Inter-trial CV for RMS amplitude from the concentric phase and 70° knee angle were 7.2% and 16.4% respectively. There were no differences in RMS amplitude, maximum knee angle or mean power across trial days. It was concluded there was acceptable reliability for all three measurements (CV < 10%), if RMS amplitude was processed from the concentric phase. Based upon the measurement reliability, the analysis system was considered suitable for monitoring power and sEMG during barbell exercise. The second study aimed to establish the reliability of muscle fibre conduction velocity (MFCV) measurements during barbell squat. This was of interest, as MFCV may provide useful information of NM recruitment and fatigue processes during resistance exercise. The study was also used as a preliminary investigation of MFCV response, in comparison to RMS amplitude, to increasing fatigue and load during squat exercise. Nine well-trained male subjects performed a series of exercises on two separate trial days. Each trial comprised isometric knee extensions at 50, 75 and 100% of MVC force, followed by barbell squats at 50, 75 and 100% of 3RM, and then a maximal bout of squat jumps at 50% 3RM load, performed until failure. sEMG measurements were recorded from a four-electrode array, secured upon the vastus lateralis. Normalised RMS amplitude was processed as above, and MFCV was processed from the inter-electrode distance and time delay between two double differentiated and correlated signals, using bespoke software. The overall value of MFCV during squat was 5.8 m.s-1. The inter-trial CV for MFCV was 9.6% during squat and 12.1% during squat jump. Based upon acceptable reliability of 10%, MFCV measurements from barbell squats were considered reliable. As expected, MFCV significantly increased with each knee extension force level (4.7 ± 1.4, 5.6 ± 1.5 and 6.2 ± 1.8 m.s-1) (p<0.01), along with RMS amplitude (p<0.0001). No differences in MFCV were found between squat loads, whilst RMS amplitude significantly increased with load (p<0.0001). Power (1920 ± 143 versus 1407 ± 254 W) and MFCV (5.7 ± 1.4 versus 4.6 ± 1.0 m.s-1) significant decreased (p<0.001) from the start to the end of the squat jump trial, with RMS amplitude unchanged. Therefore, MFCV altered with increasing fatigue, but not load, during dynamic squat exercise. It was concluded that MFCV provides useful and reliable data for acute fatigue investigations of barbell resistance exercise, in addition to sEMG amplitude measures. The following three investigations compared NM responses during and following maximum strength and power type resistance exercise sessions with different exercises, loads and movement speeds. The sessions were designed to represent elite athlete training practices, to help inform the optimisation of resistance exercise programmes. The first of these studies aimed to compare NM response to a typical maximum strength session performed with barbell squat or deadlift exercise. The purpose was to assess if technical differences between the exercises, influenced the acute NM response. Nine elite trained weightlifters performed the trial sessions of five sets of five repetitions on separate days. Normalised RMS amplitude, MFCV and power was continually measured during exercise repetitions, using the methods established above. NM function was assessed pre- and post- sessions using MVC force, central activation ratio (CAR) from superimposed stimulation during MVC, and jump performance (CMJ). The exercises were performed with subjectively matched load levels, corresponding to active muscle RPE = 17 (Borg scale), and also with controlled lifting speed. However, the squat load was lowered and raised upon the lifter’s back, whilst deadlift load was grasped in the hands, raised from the floor and then dropped. Repetition mean power was unchanged within and across sets of both sessions. Repetition RMS amplitude significantly increased (p<0.001) within sets of squat and deadlift, whilst a significant interaction between sessions and set (p<0.001) demonstrated RMS increased more during squat. Furthermore, a significant reduction in repetition MFCV was found within sets of squat (p = 0.034), but not deadlift. This suggests that motor unit activation increased during both exercises, as a response to the task of maintaining power during repetitions of whole body lifting. However, acute fatigue within squat sets led to additional increased activation as a NM compensation strategy. No pre- versus post- session differences were found for MVC, CAR or CMJ; suggesting minimal change in NM function occurred following five sets of maximum strength type resistance exercise, in well-trained subjects. The primary aim of the second study was to compare NM response and 24-hour recovery following barbell exercise maximum strength and power type sessions. The purpose was to specifically establish the degree and nature of NM response, as previous findings were unclear and barbell exercise sessions of this type have not been compared. 10 elite sprint athletes performed sessions comprising squat, split squat and push press, with four sets x repetitions per exercise. The maximum strength session exercises involved loads corresponding to active muscle RPE = 17 (Borg scale) and metronome controlled movements. The power session exercises used 30% of the maximum strength barbell load, performed as fast as possible. Repetition sEMG and power was monitored throughout each session, as above. NM function was assessed, pre-, post- and 24-hour post- each session, using the same tests as above. However, evoked peak twitch force (Pt) was also included to the pre- and post- assessments. Overall, the maximum strength session involved greater total work (p = 0.008), but lower mean power during exercise repetitions (p<0.001) in comparison to the power session. MVC and Pt force values both significantly decreased (p<0.05) pre- versus post- both sessions. However, MVC reduced more following maximum strength session (p<0.01). CAR and CMJ were unchanged post-both sessions and no differences were found between pre and 24-hour post session NM tests. The decreased Pt but not CAR findings, suggest peripheral fatigue explains the reduced force generation capacity following maximum strength and power sessions, contrary to previous resistance exercise session findings. Up to 24-hours may be required to recover force generation capacity following this volume of resistance exercise.

published_or_final_version / Medical Sciences / Master / Master of Medical Sciences

The primary purpose of this study was to observe the relationship between muscle activation of the right hand with the force produced at the fingertips in an isometric precision pinch tracking task. Thirty right-handed subjects, 15 males and 15 females, with a mean age 23.5 (SD 3.5) years, free from any neurological disorder or physical ailment, had a pair of electromyography (EMG) electrodes placed over the first dorsal interosseous (FDI) muscle, which acts on the index finger, while performing a pinch force tracking task scaled to 20% maximum voluntary contraction (MVC). The tracking task was chosen because it created a continuously increasing force application to 20% MVC and then decreasing force release from 20% MVC at a prescribed rate in both cases of 6.66% MVC force per second. In addition to showing increases in EMG activation of the FDI with increases in force, the results revealed that muscle activation for a given force level was generally greater for force application than for force release. This may be due dynamics of muscle contraction or to patterns of multiple muscle coordination. / text

Darbo tikslas - nustatyti nenutrūkstamų izometrinių susitraukimų tikslumo ir stabilumo valdymo ypatumus. Tyrimo metu kelti šie uždaviniai: 1) nustatyti ir palyginti vaizdinės grįžtamosios informacijos (VGI) ir skirtingos procentinės jėgos (SPJ) įtaką nenutrūkstamo izometrinio susitraukimo tikslumui, stabilumui ir raumenų (agonisto ir antagonisto) elektriniam aktyvumui; 2) nustatyti ir palyginti mokymosi ir potencijuojamojo krūvio įtaką nenutrūkstamo izometrinio susitraukimo tikslumui ir stabilumui. Buvo tiriami jauni, fiziškai aktyvūs vyrai (n = 8; amžius 20,0 ± 1,5 m, ūgis 182,4 ± 6,5 cm; kūno masė 73,0 ± 5,7 kg, KMI kūno masės indeksas 22,0 ± 1,7 kg/m2 (vid. ± S). Pirmojo tyrimo metu tiriamieji atliko 20%, 50% ir 70% nuo MVJ nenutrūkstamus izometrinius susitraukimus (NIS). Tiriamieji atliko 2 NIS su ir be VGI. NIS truko 13 s, tačiau buvo analizuojami tik paskutinių 10 s duomenys, nes per pirmas 3 s tiriamiesiems buvo leidžiama pasiekti reikiamą jėgą nuo MVJ ir ją išlaikyti likusias 10 s. Antrojo tyrimo metu tiriamieji atliko tokius pačius NIS kaip ir pirmojo tyrimo metu 20% jėga nuo MVJ. Tiriamieji po su VGI ir be jos atliktų NIS atliko rankos raumenų potenciaciją, kurios metu turėjo padidinti rankos lenkimo jėgą iki maksimumo ir ją išlaikyti 10 s. Pailsėję 10 s vėl atliko NIS be VGI. Visas tyrimas buvo pakartotas po 9 - erių mokymosi pratybų, kai per pratybas tiriamieji buvo mokomi atlikti greitus ir tikslius izometrinius susitraukimus 20% jėga nuo MVJ kas antrą dieną su... [toliau žr. visą tekstą] / Research aim was to establish the peculiarities of control of the accuracy and the stability of continuous isometric muscle contractions. Objectives: 1) to establish and compare effect of visual feedback on the accuracy, stability and muscle activity of continuous isometric contractions performed with different strength; 2) to establish and compare effect of learning on the dependence of accuracy and stability of a continuous isometric contraction on muscle potentiation. The subjects studied were healthy, physically active men (n = 8; age 20.0 ± 1.5 m, height 182.4 ± 6.5 cm; body mass 73.0 ± 5.7 kg, body mass index 22.0 ± 1.7 kg/m2 ( ±SD). In experiment 1, the subjects performed CIC at 20%, 50% and 70% force of MVC. The subjects performed two series of CIC – first with visual feedback information (VFI), second – without VFI. The duration of each series was 13 sec. In experiment 2, the subjects performed the same CIC at 20% force of MVC. The subjects after two series of CIC (first with VFI, second – without VFI), done potentiation load (PL), when they had to achieve maximal force and it maintain 10 sec. After 10 sec rest the subjects performed CIC without VFI. All the experiment was repeated after 9 training series. In training series, they were learning speeds – accuracy isometric contractions at 20% force of MVC. Absence of visual feedback information worsening in the accuracy of performing CIC at all forces of MVC. We have established that there is a significant... [to full text]

While military body armor is used among warfighters for protection on and off the battlefield, it has been suggested to impede performance and act as a risk factor for the development of musculoskeletal disorders, especially low back pain. Apart from personal suffering, low back pain in soldiers is a great economic burden on the US economy. The objective of this study was to quantify the changes in trunk mechanical and neuromuscular behavior following prolonged exposure to body armor compared to exposure without. A crossover study design was used where 12 sex-balanced participants completed a series of tests before and after 45 minutes of treadmill walking with and without body armor. The tests included range of motion, isometric trunk tests, sudden perturbations, and stress relaxation. As a whole, exposure duration considered in this study resulted in no significant differences in performance between armor and no armor conditions. However, comparing the effects of body armor among the sex-differentiated groups showed a body armor -induced increase in range of trunk motion in the sagittal plane among females (p = 0.0018) and a decrease in pelvic range of motion in the transverse plane among both males (p=0.025) and females (p=0.004).

The purpose of this study was to determine the effectiveness of a modified sitting position straight leg raise on vastus medialis oblique (VMO) strength and EMG activity as compared to a traditional straight leg raise. A total of twenty-three subjects were recruited for this study. The subjects were randomly assigned to one of the following groups: (group I) modified straight leg raise (MSLR), and (group II) straight leg raise (SLR). The exercise program was three weeks long. University procedures for the protection of human subjects were followed. The subjects began with a 5 minute warm-up on a Cybex stationary bike set at 90 revolutions / minute. The subject then had electrodes placed on the Vastus Lateralis (VL) and Vastus Medialis Oblique (VMO). A Macintosh computer was used to record the EMG data. The subject then performed a standard Cybex test for knee flexion and extension. The Cybex dynamometer was placed at the knee joint line, the chair back tilt was at 85 degrees, the hip, chest, and thigh restraints were all fastened. The subjects in group I (Modified sitting SLR) and II (SLR) then returned the next day for their first rehabilitation lesson. Each subject group then participated in their respected exercise program for a total of three weeks. After three weeks of rehabilitation, the subjects retested using the same procedures followed in the pretest. A two tailed t-test was used to determine significance of the difference between means of the two groups. No significant differences were found between the two groups. / School of Physical Education

The purpose of this study was to determine the vastus medialis oblique muscular electromyographical (EMG) activity during two therapeutic exercises: the modified straight leg raise and the traditional straight leg raise. Two subject groups of 10 subjects each, one with anterior knee pain (PHY) and the other group with no history of patellofemoral pathology (NORM), performed the traditional straight leg raise (SLR) and a modified straight leg raise with external hip rotation (MOD). Each subject performed an isometric maximum voluntary contraction and three trials of each of the two therapeutic exercises. The EMG variables analyzed were the percent of the maximum voluntary contraction for each muscle, vastus medialis oblique, vastus lateralis, and rectus femoris: the percent of the maximum voluntary contraction of the ratio between the vastus medialis oblique and the vastus lateralis; the percent of the maximum voluntary contraction for the integrated EMG for each muscle; and the percent of the maximum voluntary contraction for the root mean square for each muscle. The statistical analysis was conducted with two-way analysis of variance procedures. The statistical analysis revealed no significant differences; however, the data appeared to illustrate a trend toward more electromyographical activity in the vastus medialis oblique in the PHY subject group during the MOD therapeutic exercise. This suggests that the MOD therapeutic exercise may be able to isolate the vastus medialis oblique muscle in persons with anterior knee pain and allow them to regain strength and normal function earlier than with the use of the SLR therapeutic exercise. / School of Physical Education

The main purpose of this study was to investigate the relationship between human growth hormone (hGH) and two separate components of resistance exercise. Eight non-weight-trained subjects (23.33 ± 0.3 yrs) performed three force production trials (FPT), at different concentric workloads, and an 120% eccentric exercise trial (EET) on the Cybex 6000. Blood samples (3 mls) were taken pre- and post-exercise and analyzed for lactate, creatine kinase (CK) and hGH. Electromyographic (EMG) activity of the quadriceps muscle was recorded during each trial. The mean peak torque produced during the FPTs increased as work intensity increased but was the highest in the EET. The data for total work showed a proportional relationship with the intensity of the three concentric work loads but not the 120% EET. EMG activity of vastus medialis (VM) and rectus femoris (RF) measured during EET was 26% less than RF of 50% and 15% less than VL of 70% in FPT, respectively. The highest hormonal response occurred following the 120% EET. The hormonal response following the FPTs was highest in the 90% FPT with the two lower work intensity trials (50 and 70%) showing no clear hormonal response. Although the hGH response was the highest in the 120% EET, the post-exercise lactic acid levels in EET were 24% less than that of the 90% FPT. Creatine kinase (CK) activity was significantly elevated 36 hours after the last bout of EET which suggests that the eccentric exercise resulted in muscle damage. The results from concentric trials showed that muscle force generation, EMG, and lactic acid of the three different concentric trials were well correlated to the pattern of hGH secretion. However, only peak torque was consistent with the hGH response of the EET. The highest peak torque and hGH levels were achieved with eccentric exercise. The highest levels of fatigue, as a result of the combination of longer exercise time and overloading of the muscle during EET, may explain the higher hGH output. The muscle damage caused by the eccentric trial was enough to induce delayed onset of muscle soreness and may be the stimulus for the higher hGH output. The hGH response may facilitate repair of the muscular damage induced by eccentric exercise by promoting protein synthesis. / School of Physical Education

Progressive resistance training (PRT) in the elderly has commonly used ATPase histochemistry to evaluate fiber type changes, but evidence shows there are myosin heavy chain (MHC) hybrids in aging muscle that cannot be classified by histochemistry. The purpose of this study was to assess the MHC and whole muscle alterations following a 12-week PRT protocol. Seven healthy men (age=74.0±4.7, weight=74.6±13.5kg) underwent testing for 1-repetition maximum (1-RM), whole muscle (thigh) crosssectional area (CSA) by computed tomography, and a needle muscle biopsy from the vastus lateralis for analysis of MHC, pre- and post-training. The PRT consisted of 2 sets of 10 repetitions, and a third set to volitional exhaustion at 80% 1-RM, 3 days per week for 12 weeks. Muscle ATPase histochemistry analysis for distribution did not significantly differ following training. Muscle samples were freeze dried and dissected for MHC analysis (sodium dodecyl sulfate-polyacrylamide gel electrophoresis (5% gel) and silver stained; 224.0±11.2 and 213.0±8.1 fibers/subject pre-/post-training; total fibers analyzed=3059). MHC analysis demonstrated significant increases in MHC I proportion (10.4%; P<0.05), and significant decreases in MHC UIIa (9.0%; P<0.05), UIIa/x (0.9%; P<0.05), and IIa/x (8.9%; P<0.05) isofroms, along with no change in the MHC Ila and IIx isoforms, pre- versus post-training. In addition, 1-RM (51.9%; P<0.05) and CSA (5.9%; P<0.05) increased from pre- to post-testing. This data supports previous whole muscle changes, more important, is the increase in MHC I and decrease in MHC I/IIa, I/IIa/IIx, and IIa/x hybrids. The myosin light chain 3f (MLC3f) to MLC 2 ratio did not change with the PRT in either the MHC I or MHC IIa isoforms, although there was a significantly greater amount of MLC 3f in the MHC Ila versus the MHC I fibers (p<0.05), pre- and post-training. The myosin isofrom data provides support that aging muscle has the plasticity to adapt in a manner unlike that of young muscle. / School of Physical Education