The aim of this study was to compare the possible changes in muscle activation level between a first and second bout of damaging eccentric exercise performed at 2 weeks interval (i.e. repeated bout effect). To that purpose, ten physically active males took part in this study. The eccentric exercise consisted of 10 sets of 12 maximal voluntary contractions (MVC) produced by the knee extensors during movements performed at a constant speed of 160 degrees s(-1). Changes in voluntary and electrically evoked torque in concentric and/or isometric conditions were assessed at the following time points: pre-exercise, and 2 min, 1 and 24 h after each eccentric exercise. At the same time points, voluntary activation was quantified by the superimposed electrical stimulation technique. Muscle soreness and plasma CK activity were measured within 48 h after the eccentric exercise. The results showed that the decrease in eccentric peak torque was linear throughout the exercise protocol. At the end of bouts 1 and 2, torque was significantly reduced by 27.7 +/- 9.1 and 23.4 +/- 11.2, respectively, with no difference between bouts (P > 0.05). At 24 h post-exercise, a lower reduction (P < 0.05) in MVC (17.8 +/- 5.4%) and electrically evoked (16.7 +/- 4.6%) isometric torque was observed for bout 2. In contrast, no statistical difference was found in the deficit in voluntary activation between the two bouts. In conclusion, our results indicate that the repeated bout effect of eccentric exercise appears to reduce muscle damage, but does not influence the level of voluntary activation.

Ultrasonography is a reliable method to measure the anterior capsular distance in THA, especially if performed by an experienced examiner.

The aim of the study was to establish the impact of hyperthermia and dehydration on maximum voluntary contraction (MVC) force and central fatigue, as well as to assess the impact of rehydration on the function of skeletal muscle in conditions of hy-perthermia when performing isometric exercise of maximum intensity for 2 minutes. The subjects were adult females (n = 8) not actively engaged in sports, aged 21.2 ± 2.4 years, body mass — 64.84 ± 8.4 kg and height — 170.8 ± 2.5 cm respectively.Three studies were carried out: one control study and two experimental ones. During the fi rst experiment the bodies of the participants in the study were subjected to hyperthermia and dehydration (the subjects sat immersed up to the pelvis in hot water (44 ± 1 o C) bath for 45 min). During another experiment, the same methods of increasing hyperthermia being used, the bodies of the subjects experienced oral rehydration with 1000 ml NaCl 0.9% solution of 37 o C. The MVC load lasted for 120 s (MVC-2 min) and every 15 s the muscle was stimulated by electrical impulses: the duration of the stimulation was 250 ms, the frequency — 100 Hz and the voltage — 85—105 V accordingly. We registered the movement of MVC (N * m) and the degree of voluntary activation of muscles according to the formula VA% = (MVF + electrical im-pulse) / MVF * 100. When the load was applied the subjects were motivated verbally and they were provided with the visual feedback of changes in force signals. After hyperthermia and dehydration was applied, the rectal body temperature increased from 37.48 ± 0.25 to 39.5 ± 0.23 o C (p < 0.001), and the inner temperature of the muscle (3 cm deep) — from 36.91 ± 0.29 to 39.83 ± 0.31 o C (p < 0.001) on the average. During the hyperthermia experiment the subjects had lost 0.4 ± 0.07 kg in weight on the average, and that was 0.62 ± 0.13% of their body mass. After oral rehydration in conditions of hyperthermia body mass of the subjects had increased by 0.48 ± 0.01 kg on the average, i. e. by 0.74 ± 0.08% of their body mass. Having analyzed the physiological index of heat stress (in the 10-point system) we have found that during both experiments the subjects had experienced a physiological stress of an extremely high level, e. g. in the case of hyperthermia — 8.85 ± 1.13 points and in the case of rehydration — 8.38 ± 0.98 points respectively. There was a signifi cant decrease (p < 0.001) in MVC at the 3rd second of the load during both experimental researches and control research — at the 15th second of the load. These changes in MVC remained until the end of the 2nd min, compared to the indices registered before the load. During recovery, 5 min (A 300) after the load applied, MVC during control and experimental (hyperthermia) research had regained the level registered be-fore the load (p > 0.05). Two-factor dispersion analysis revealed that the changes in the force in this case depended on time (p < 0.001), as well as on the body state (p = 0.001), whereas interaction of time and body state had no signifi cant effect on the result (p > 0.05).After the analysis of the indices of voluntary activation we noticed that hyperthermia (p < 0.05) and rehydration (p < 0.01) had signifi cantly increased the degree of voluntary activation (VA%), compared to the one established before the load. During the recovery time, 15 s after the load had been undertaken, the force index of voluntary activation regained the level that had been registered before the load. Two-factor dispersion analysis allowed us to establish that the changes in the force indices of voluntary activation depended on time (p < 0.001), the body state (p = 0.047) and the interaction between them (p < 0.05).Applying the methods of passive muscle heating the participants in the study were subjected to hyperthermia and 1 o  dehy-dration. Hypertension increased the central fatigue. During the experiments of hyperthermia and dehydration MVC force fatigue altered homogeneously. In conditions of hyperthermia, rehydration had a negative impact on the central fatigue and increased it even more when maximum isometric load for 2 min had been undertaken.

Atliekant fi zinius pratimus, kasdienės veiklos veiksmus, dažnai tam tikrą laiką kūnas turi išlaikyti statinę pusiausvyrą. Pusiausvyros stabilumas svarbus kai kuriomis neurologinėmis ligomis sergantiesiems, senyvo amžiaus žmonėms. Pusiausvyrą dažnai tenka išlaikyti įtempus raumenis. Tyrimo tikslas — ištirti, kaip kinta pusiausvyros stabilumas ramiai stovint atpalaidavus ir įtempus kojų raumenis. Remiantis atvirkštinės svyruoklės modeliu, raumenų įtempimas turėtų padidinti pusiausvyros stabilumą. Buvo tiriami 44 Lietuvos kūno kultūros akademijos studentai (18 vaikinų ir 26 merginos). Jų amžius — 22—26 m., ūgis — 174,9 ± 9,4 cm, svoris — 68,7 ± 13,8 kg. Naudojant MYOTON-3 prietaisą, miotonometrijos metu išmatuotas įtempto ir atpalaiduoto dvilypio blauzdos raumens vidinės galvos standumas. Vertintas raumens virpesių dažnis, virpesių logaritminis dekrementas ir standumo koefi cientas (K). Naudojant serijinės gamybos jėgos plokštę MA-1 ir kompiuterinę įrangą registruojamiems signalams analizuoti, statinės posturografi jos metodu užregistruota stabi-lograma tiriamajam stovint atpalaidavus ir įtempus kojų raumenis. Registruojamo signalo diskretizacija — 10 ms. Stabilogramos registravimo trukmė — 60 s. Vertintas slėgio centro (SC) didžiausias poslinkis skersinėje (Δx) ir strėlinėje ašyse (Δy), SC svyravimo vidutinis greitis ( v ). Kojų raumenų įtempimas reikšmingai (p < 0,01) padidino Δx nuo 22,14 ± 1,04 iki 26,00 ± 1,28 mm, Δy — nuo 25,53 ± 1,60 iki 34,86 ± 2,41,  v  — nuo 11,49 ± 0,39 iki 18,88 ± 0,86 mm / s, K — nuo 333,29 ± 11,16 iki 471,24 ± 16,93 N / m. Stabilogramos signalo dekompozicijai nustatyti taikyta diskretinė vilnelių transformacija (buvo naudojamos Daubechie šeimos 4 eilės vilnelės). Išskirti 6 signalo sandai. Pastebėtas ryškus ir patikimas sando galios padidėjimas įtempus kojų raumenis esant aukštesniems dažniams (5,0—0,625 Hz). Tai rodo, kad įtempus kojų raumenis SC svyravimų dažnio spektras pasislinko aukštesnių dažnių link. Norėdami įvertinti ryšį tarp dvilypio blauz-dos raumens standumo ir stabilometrinių dydžių, skaičiavome stabilometrinių ir miometrinių duomenų koreliacijos koefi cientus. Pastebėtas gana stiprus — 0,651 (p < 0,01) koreliacinis ryšys tarp K ir  v  rodiklių. Didelis determina-cijos koefi cientas (r 2  ≈ 0,9) tarp sando galios ir  v  nustatytas aukštesnių dažnių srityje (5,0—0,625 Hz). Šioje srityje pastebėtas taip pat gana stiprus koreliacinis ryšys tarp sando galios ir raumens standumo — r ≈ 0,6. Apibendrinant tyrimų duomenis galima teigti: a) kojų raumenų įtempimas sumažina žmogaus pusiausvyros stabilumą ramiai stovint; b) įtempus kojų raumenis, SC svyravimų spektre ima vyrauti aukšti dažniai.

It has been established that muscle torque variability determines movement stability during the task [1]. Calf muscle weakness, ankle range of motion reduction and postural misbalance are common pathological limitations after Achilles tendon rupture (ATR). Most studies analyse rehabilitation influence for muscle strength and body balance, but there is a lack of information about calf muscle torque variability. The aim of the study was to determine ankle plantar flexion and dorsal flexion muscle maximal voluntary contraction torque and variability Q. Organization and methods. We measured five males, (aged 29 ± 6) after 6.5 – week surgery of ATR. Participants performed isometric ankle flexion and extension force with injured and non-injured legs. Muscles maximal voluntary contraction (MVC) torque and torque variability were measured at –15°; 0°; 15° angles. The variability of target force was 20% of MVC torque. Rehabilitation programme consisted of balance, muscle strength and stretching exercises. Calf muscle MVC torque and variability were observed before and after 8-week rehabilitation. The results of the research. We determined that after physiotherapy the injured and the non-injured leg isometric ankle flexion and extension muscle MVC torque increased and muscle torque variability decreased.Keywords: muscle torque variability, isometric maximal voluntary contraction torque, rehabilitation suformavimas.