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Background: Total hip arthroplasty (THA) is very effective in alleviating pain, but functional deficits persist up to a year following surgery. Regardless of standard physiotherapy programs, significant additional muscular atrophy and weakness occur. Deficits in strength have serious adverse consequences for these patients with respect to physical function, the maintenance of independence, and the requirement for revision surgery. Progressive resistance training in rehabilitation following THA has been shown to significantly enhance muscle strength and function. The fundamental principle is to progressively overload the exercised muscle as it becomes stronger. Different strength training protocols have been used at different times in the postoperative phase, in group or individual practices, with major differences being in center-based and home-based programs with or without supervision. The primary objective of our study is to evaluate whether an early postoperative home-based strength training protocol can improve patient functional outcomes at 3 months and 1 year following surgery. Secondary objectives are the feasibility of the presented protocol for all elective THA patients and its safety., Methods/design: This study is a prospective multicenter randomized clinical trial to be conducted in the orthopedic departments of two Slovenian hospitals. In each hospital, 124 patients aged 60 or older with unilateral osteoarthritis, an ASA score between 1 and 3, a signed informed consent form, and no terminal illness disabling rehabilitation participation will be randomly assigned to the intervention or control group. THA with an anterior approach will be performed. All patients will receive current standard physiotherapy during hospitalization. Patients in the intervention group will also learn strength and sensory-motor training exercises. Upon discharge, all will receive USB drives with exercise videos, written exercise instructions, and a training diary. Physiotherapists will perform the assessments (physical tests and the maximal voluntary isometric contraction assessment), and patients will fill out outcome assessment questionnaires (the Harris Hip Score and 36-Item Short Form Health Survey) at baseline and 1, 3, and 12 months after surgery., Discussion: The main purpose of our study is to design a new standardized rehabilitation protocol with videos that will be effective, safe, and accessible to all Slovenian THA patients., Trial Registration: ClinicalTrials.gov NCT04061993 . Registered on 07 November 2019. Protocol ID: PRT_PhD. Version 1., (© 2022. The Author(s).)

SLOfit Lifelong is a public health initiative which was created to upgrade a well-established, national physical fitness surveillance system for Slovenian schoolchildren that has been collecting annual fitness and health data for over three decades. The ultimate objective of creating SLOfit Lifelong was to build a modern societal infrastructure with the capacity and ability to detect future causal associations between childhood physical fitness trends and future health outcomes based on the lifelong surveillance of one's own fitness status. By instilling citizens with an ambition to test, understand, and follow-up their own physical fitness and health status (including related health risk factors), this initiative provides the technical support and expert feedback needed to engender greater individual control over understanding (and thus modulating), one's own physical fitness status as they progress into older adulthood. This perspective paper details the extensive approach taken to devise appropriate fitness test batteries for adults and older adults which can also relate to the student version of the original SLOfit test database, including establishing criterion health risk zones and a public approach to establish this national, citizen-driven health feedback framework. Through its sophisticated online web applications, social media, print media, and outreach workshops, SLOfit Lifelong provides the expert support for public health engagement by fostering positive lifelong physical literacy experiences an individual can enjoy across their aging journey., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2022 Jurak, Morrison, Soric, Leskošek, Kovač, Ocvirk, Sember, Kramaršič, Meh, Potočnik, Blagus, Markelj, Golja, Strojnik, Hadžić and Starc.)

(1) Speed endurance training (inducing a high blood lactate concentration) delays excitation-contraction coupling impairment, thus providing more space for high-frequency fatigue to occur in the early stage of maximal concentric actions. This study aimed to test the hypothesis that the maintenance type of speed endurance training may shift peripheral fatigue from low-frequency to high-frequency fatigue after the 15 s long Wingate test. (2) Six students of physical education performed the corresponding training for six weeks. Before and after this period, they were tested for low- and high-frequency fatigue after the 15 s long Wingate test; additionally, their blood lactate concentrations, maximal cycling power, work, fatigue index, and muscle twitch responses were also tested. (3) The training increased the maximal cycling power and work ( p < 0.001 and p < 0.01, respectively) with minor changes in the mean fatigue index and blood lactate concentration (both p > 0.05). Low-frequency dominant fatigue before the training showed a trend toward high-frequency dominant fatigue after the training ( p > 0.05). (4) The results showed that the 15 s Wingate test failed to induce significant high-frequency fatigue. Even though it displayed a substantial fatigue index, the changes in favor of high-frequency fatigue were too small to be relevant.

The aim of the study was to test whether ascending to a moderate real altitude affects motoneuron pool excitability at rest, as expressed by a change in the H-reflex amplitude, and also to elucidate whether a possible alteration in the motoneuron pool excitability could be reflected in the execution of lower-body concentric explosive (squat jump; SJ) and fast eccentric-concentric (drop jump; DJ) muscle actions. Fifteen participants performed four experimental sessions that consisted of the combination of two real altitude conditions [low altitude (low altitude, 690 m), high altitude (higher altitude, 2,320 m)] and two testing procedures (H-reflex and vertical jumps). Participants were tested on each testing day at 8, 11, 14 and 17 h. The only significant difference ( p < 0.05) detected for the H-reflex was the higher H-reflex response (25.6%) obtained 15 min after arrival at altitude compared to baseline measurement. In terms of motor behavior, DJ height was the only variable that showed a significant interaction between altitude conditions (LA and HA) and time of measurement (8, 11, 14 and 17 h) as DJ height increased more during successive measurements at HA compared to LA. The only significant difference between the LA and HA conditions was observed for DJ height at 17 h which was higher for the HA condition ( p = 0.04, ES = 0.41). Although an increased H-reflex response was detected after a brief (15-20 min) exposure to real altitude, the effect on motorneuron pool excitability could not be confirmed since no significant changes in the H-reflex were detected when comparing LA and HA. On the other hand, the positive effect of altitude on DJ performance was accentuated after 6 h of exposure., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2022 Štirn, Garcia-Ramos, Feriche, Strojnik and Tomažin.)

Abstract: Tomazin, K, Strojnik, V, Feriche, B, Garcia Ramos, A, Štrumbelj, B, and Stirn, I. Neuromuscular adaptations in elite swimmers during concurrent strength and endurance training at low and moderate altitudes. J Strength Cond Res 36(4): 1111-1119, 2022-This study evaluated neuromuscular adaptations in elite swimmers during concurrent strength and endurance training (SET) at low (295 m) and moderate (2,320 m) altitudes. Sixteen elite swimmers took part in a 3-week SET during a general preparation phase. All neuromuscular tests were performed a week before and after a SET. In posttraining, maximal knee isometric torque (TMVC) and soleus H-reflex remained statistically unchanged for sea-level (SL) and for altitude (AL) training. Rate of torque development (RTD) decreased post-SL (-14.5%; p < 0.01) but not post-AL (-4.7%; p > 0.05) training. Vastus lateralis electromyographic (EMG) activity during RTD decreased post-SL (-17.0%; P = 0.05) but not post-AL (4.8%; p > 0.05) training. Quadriceps twitch torque (TTW) significantly increased post-AL (12.1%; p < 0.01) but not post-SL (-1.0%; p > 0.05; training × altitude: F1,15 = 12.4; p < 0.01) training. Quadriceps twitch contraction time and M-wave amplitude remained statistically unchanged post-SL and post-AL training. After SL training, increment in TMVC was accompanied with increment in vastus lateralis EMG (R = 0.76; p < 0.01) and TTW (R = 0.48; p < 0.06). Posttraining in AL, increment in TMVC was accompanied with increment in TTW (R = 0.54; p < 0.05). Strength and endurance training at altitude seems to prompt adaptations in twitch contractile properties. In contrast, SET performed at SL may hamper the magnitude of neural adaptations to strength training, particularly during rapid voluntary contractions. In conclusion, SET at AL might benefit muscular adaptations in swimmers compared with training at SL., (Copyright © 2020 National Strength and Conditioning Association.)

We propose a new exercise, the abdominal rise on the ball, to replace the traditional crunch in exercise programs. The aim of this study is to compare the activity of the abdominal muscles when performing an ARB with the same activity when performing a traditional crunch. Twenty healthy adults participated in the study. Surface electromyography (EMG) was recorded from the upper and lower rectus abdominis (URA, LRA), internal oblique (IO), external oblique (EO), transversus abdominis (TrA), and erector spinae (ES). EMG values were normalized to maximal voluntary isometric contraction. A paired t -test, nonparametric Wilcoxon test and correlation coefficient were used for statistical analysis. The normalized EMG values of EO, TrA and ES, were statistically significantly higher during the abdominal rise on the ball compared to the traditional crunch, while URA, LRA and IO were significantly lower during the abdominal rise on the ball compared to the traditional crunch. TrA, EO and IO are sufficiently activated during an abdominal rise on a ball, so the exercise could be deemed effective for strengthening these muscles.

Background: Blood flow-restricted resistance training (BFR-RT) has been proven to be safe and efficacious in healthy older adults, but not in cardiovascular disease., Objective: The aim of this study was to investigate the acute and training induced effects of BFR-RT on hemostatic and hemodynamic responses in patients with coronary artery disease (CAD)., Methods: Stable patients with CAD were randomized to 8 weeks of BFR-RT (30%-40% 1-repetition maximum unilateral knee extension) combined with aerobic training or aerobic training alone (control group). At baseline and after 4 and 8 weeks, blood samples were taken before and after BFR exercise, whereas hemodynamic parameters were monitored throughout the exercise., Results: Twenty-four patients (12 per group; mean age, 60 ± 2 years; mostly male [75%]) completed the study. The BFR-RT significantly improved systolic blood pressure (-10 mm Hg; P = .020) and tended to lower diastolic blood pressure (-2 mm Hg; P = .066). In contrast, no posttraining alterations were observed in N-terminal prohormone B-type natriuretic hormone, fibrinogen, and D-dimer values. During BFR exercise, all hemodynamic variables significantly increased after the first and second set, whereas blood pressure immediately lowered after the cuff was released in the third set. Last, significant interaction was only observed for repetitions × intensity (P < .001; partial η2 = 0.908) of diastolic blood pressure at higher exercise intensity (40% 1-repetition maximum)., Conclusions: The BFR-RT was proven to be safe, with favorable hemodynamic and hemostatic responses in patients with CAD, and can be recommended as an additional exercise modality in cardiac rehabilitation.Trial Registration:ClinicalTrial.gov Identifier: NCT03087292., Competing Interests: The authors have no conflicts of interest to disclose., (Copyright © 2020 Wolters Kluwer Health, Inc. All rights reserved.)

The aim of this study was to investigate neuromuscular adaptations in elite judo athletes after three weeks of power-oriented strength training at terrestrial altitude (2320 m). Nineteen men were assigned to altitude training (AL) (22.1 ± 2.3 years) and sea level training (SL) (22.6 ± 4.1 years). Neuromuscular assessment consisted of: (1) maximal isometric knee extensor (KE) torque, (2) KE rate of torque development (RTD), (3) quadriceps activity and voluntary activation, (4) soleus H-reflex, (5) quadriceps single (T TW ) and double twitch torque (T DB100 ) and contraction time (CT TW ). There were no significant differences between groups at baseline for any of the observed parameters. Significant differences were found between groups in terms of change in RTD ( p = 0.04). Cohen's d showed a positive significant effect (0.43) in the SL group and a negative significant effect (-0.58) in the AL group. The difference between groups in changes in CT TW as a function of altitude was on the edge of significance ( p = 0.077). CT TW increased by 8.1 ± 9.0% in the AL group ( p = 0.036) and remained statistically unchanged in the SL group. Only the AL group showed a relationship between changes in T TW and T DB100 and changes in RTD at posttest ( p = 0.022 and p = 0.016, respectively). Altitude induced differences in muscular adaptations likely due to greater peripheral fatigue.

Background: There is insufficient knowledge about how aerobic exercise impacts the disease process of multiple sclerosis, which is characterized by accumulation of white matter lesions and accelerated brain atrophy., Objective: To examine the effect of aerobic exercise on neuroinflammation and neurodegeneration by magnetic resonance imaging and clinical measures of disease activity and progression in persons with multiple sclerosis., Patients and Methods: An exploratory 12-week randomized control trial including an intervention group (n = 14, 12 weeks of aerobic exercise twice weekly) and a control group (n = 14, continuation of usual lifestyle). Primary outcomes were magnetic resonance imaging measures (lesion load, brain structure volume change), while secondary outcomes included disability measures, blood cytokine levels, cognitive tests and patient-reported outcomes., Results: The effects of aerobic exercise on whole brain and grey matter atrophy were minor. Surprisingly, the observed effect on volume (atrophy) in selected brain substructures was heterogeneous. Putaminal and posterior cingulate volumes decreased, parahippocampal gyrus volume increased, thalamus and amygdala volume remained the same, and active lesion load and count decreased. However, apart from weak improvements in walking speed and brain-derived neurotrophic factor levels, there was no effect of aerobic exercise on other clinical, cognitive or patient-reported outcomes., Conclusion: These results suggest that aerobic exercise in persons with multiple sclerosis has a positive effect on the volume of some of the substructures of the brain, possibly indicating a slowing of the neurodegenerative process in these regions, but a negative impact on the volume of some other substructures, with unclear implications. Further research is needed to determine whether the slight decrease in active lesion volume and count implies an anti-inflammatory effect of aerobic exercise, and the exact significance of the heterogeneous results of volumetric assessments.

Background: The aim of the study was to address the working population with an occupational stress prevention program using mHealth solution and encourage them for healthy lifestyle choices., Methods: Seventeen participants were randomized from the corporate setting. A 24alife app with a good compliance program was selected. Test battery has been designed to test the physical readiness, psychological evaluation and biological blood markers for stress. Participants were followed up after 30, 60 and 90 days, respectively, within the intervention period. Weight of participants was tracked three times per month. Univariate analysis compared the continuous variables by One-Way Repeated-Measures ANOVA test when the data were normally distributed, or Wilcoxon rank sum test for abnormal distribution of variables., Results: Participants used the app with a compliance rate of 94.1%. The psychological evaluation revealed higher motivation for work, lower burnout scores and participants gave subjective responses of better general wellbeing. Some of the participants lost up to four kg of body mass. Physical readiness has also improved., Conclusions: Results of mHealth projects on corporate could include primary health care institutions and health ministry to extend the existing system to patients' pockets where they can monitor their disease and increase the ability of self-care.

Background: Whole body vibrations have been used as an exercise modality or as a tool to study neuromuscular integration. There is increasing evidence that longer WBV exposures (up to 10 minutes) induce an acute impairment in neuromuscular function. However, the magnitude and origin of WBV induced fatigue is poorly understood., Purpose: The study aimed to investigate the magnitude and origin of neuromuscular fatigue induced by half-squat long-exposure whole-body vibration intervention (WBV) with sets of different duration and compare it to non-vibration (SHAM) conditions., Methods: Ten young, recreationally trained adults participated in six fatiguing trials, each consisting of maintaining a squatting position for several sets of the duration of 30, 60 or 180 seconds. The static squatting was superimposed with vibrations (WBV 30 , WBV 60 , WBV 180 ) or without vibrations (SHAM 30 , SHAM 60 , SHAM 180 ) for a total exercise exposure of 9-minutes in each trial. Maximum voluntary contraction (MVC), level of voluntary activation (%VA), low- (T 20 ) and high-frequency (T 100 ) doublets, low-to-high-frequency fatigue ratio (T 20/100 ) and single twitch peak torque (TW PT ) were assessed before, immediately after, then 15 and 30 minutes after each fatiguing protocol., Result: Inferential statistics using RM ANOVA and post hoc tests revealed statistically significant declines from baseline values in MVC, T 20 , T 100 , T 20/100 and TW PT in all trials, but not in %VA. No significant differences were found between WBV and SHAM conditions., Conclusion: Our findings suggest that the origin of fatigue induced by WBV is not significantly different compared to control conditions without vibrations. The lack of significant differences in %VA and the significant decline in other assessed parameters suggest that fatiguing protocols used in this study induced peripheral fatigue of a similar magnitude in all trials., Competing Interests: Ramona Ritzmann is employed by Praxisklinik Rennbahn AG. The authors declare there are no competing interests., (©2020 Kalc et al.)

Background: Health care professionals are exposed to the psychological and physiological effects of stress, which is a well-known risk factor for various mental and physical health problems., Objective: The aims of this study were to assess the adherence of female health care workers to use a web-based tool for improving and modifying lifestyle and to identify the potential factors influencing their adherence., Methods: A prospective, observational study was performed. A total of 80 female health care workers (physicians and gradated nurses) from 2 university medical centers and female members of a family medicine society participated. Participants completed a questionnaire that inquired about their basic demographic data and physical fitness. Physical fitness was assessed by the Rockport Fitness Walking Test. Adherence to a web-based application (24@life) was followed for 3 months and the number of log-ins into the application was counted., Results: The study was conducted from March to October 2019. Significantly high workload has been detected in all groups (P<.05), except in the general practitioner with normal workload group. The graduated nurse working in the surgery room group showed chronic stress with elevated S-cortisol levels (>690 nmol/L); activated cellular immune system with elevated concentrations of lymphocytes (reference 1.1-2.5 × 10 9 cells/L), CD3 cells (reference 0.7-1.9 × 10 9 cells/L), CD8 cells (reference 0.2-0.7 × 10 9 cells/L), and HLA-DR/CD3 cells (reference 0.04-0.2 × 10 9 cells/L); and the worst quality of sleep (mean 2.8 [SD 1.2]). Only 32 of 80 participants (40%) were adherent to the web-based application. Participants most frequently viewed web pages on areas of physical activity (497 times) and nutrition (332 times). No factors or participant's characteristics such as weight (odds ratio [OR] 1.026, 95% CI 0.977-1.078), BMI (OR 0.993, 95% CI 0.834-1.184), age (OR 0.970, 95% CI 0.910-1.034), or stress level (OR 0.997, 95% CI 0.995-1.000) were identified to affect the adherence rates., Conclusions: Female health care workers exposed to high workload did not find the web-based application useful for improving and modifying their lifestyle. Therefore, other strategies that might help health care workers facing stress and improve their lifestyle should be identified., (©Tomislav Jukic, Alojz Ihan, Marija Petek Šter, Vojko Strojnik, David Stubljar, Andrej Starc. Originally published in the Journal of Medical Internet Research (http://www.jmir.org), 14.08.2020.)

Few, if any, studies have reported the effects of intensity of balance exercise for balance training and rehabilitation. The aim of the present study was to find a relative measure of intensity of balance exercise. On this basis, we analysed ankle muscle activation in the sagittal plane with increasing difficulty for a one leg stance on a T-board. Ten adults (7 men, 24.1 ± 3.5 years; 3 women, 30.6 ± 5.8 years) performed 3 trials on a T-board within 6 randomly assigned stability levels. T-board swaying velocities in the sagittal plane were manipulated to attain different stability levels (conditions). Concurrently, angular distance of the T-board and active balance time (i.e., percentage of a total time balancing) under each condition were measured. Surface electromyography from the tibialis anterior, gastrocnemius and soleus were monitored during one leg stance. The surface electromyography amplitude in the time domain was quantified using the root-mean-square values. Significant effect of stability levels on angular distance (F 5,45 = 3.4; p = 0.01) and velocity of the T-board (F 5,45 = 4.6; p = 0.002) were obtained. Active balance time decreased by ∼15% (p = 0.001) from the maximal to the minimal stability conditions. The graded level of balance board stability conditions did not generate significantly higher root-mean-square values in any muscles and hence could not be used as a relative measure of intensity of balance exercise. These findings imply that there could be a plateau in difficulty of balance exercise for enhancement of ankle muscle activity., (© 2019 Jerica Licen, Vojko Strojnik, Katja Tomazin, published by Sciendo.)

Resistance training may be associated with unfavorable cardiovascular responses (such as hemodynamic alterations, anginal symptoms or ventricular arrhythmias). In healthy adults, blood flow-restricted (BFR) resistance training improves muscle strength and hypertrophy improvements at lower loads with minimal systemic cardiovascular adverse responses. The aim of this study was to assess the safety and efficacy of BFR resistance training in patients with coronary artery disease (CAD) compared to usual care. Patients with stable CAD were randomized to either 8 weeks of supervised biweekly BFR resistance training (30-40% 1RM unilateral knee extension) or usual exercise routine. At baseline and after 8 weeks, patients underwent 1-RM knee extension tests, ultrasonographic appraisal of vastus lateralis (VL) muscle diameter and of systemic (brachial artery) flow-mediated dilation, and determination of markers of inflammation (CD40 ligand and tumor necrosis factor alfa), and fasting glucose and insulin levels for homeostatic model assessment (HOMA). A total of 24 patients [12 per group, mean age 60 ± 2 years, 6 (25%) women] were included. No training-related adverse events were recorded. At baseline groups significantly differ in age (mean difference: 8.7 years, p < 0.001), systolic blood pressure (mean difference: 12.17 mmHg, p = 0.024) and in metabolic control [insulin ( p = 0.014) and HOMA IR ( p = 0.014)]. BFR-resistance training significantly increased muscle strength (1-RM, +8.96 kg, p < 0.001), and decreased systolic blood pressure (-6.77 mmHg; p = 0.030), whereas VL diameter (+0.09 cm, p = 0.096), brachial artery flow-mediated vasodilation (+1.55%; p = 0.079) and insulin sensitivity (HOMA IR change of 1.15, p = 0.079) did not improve significantly. Blood flow restricted resistance training is safe and associated with significant improvements in muscle strength, and may be therefore provided as an additional exercise option to aerobic exercise to improve skeletal muscle functioning in patients with CAD. Clinical Trial Registration: www.ClinicalTrials.gov, identifier: NCT03087292.

Background: Being aware of ankle movement and motor control has a critical role in maintaining balance during functional activities such as standing, walking, and running. Since the somatosensory system declines with aging, this is even more important for older adults., Research Question: How do different exercise modalities (static stretching, one-leg balance task, concentric contractions, and control) acutely influence ankle motion sense in young and older adults?, Methods: Seventeen young and fifteen older participants performed four different intervention protocols (static stretching, one-leg balance task, concentric contractions, and control) in random order. Each session comprised measurements of ankle motion sense in plantar flexion (PF) and dorsal flexion (DF) directions prior to and after an intervention protocol. Average threshold levels (in degrees) of motion sense detection were calculated from three trials in each direction (PF/DF)., Results: A lower threshold of motion ankle sense was observed for young adults compared to older adults regardless of the exercise modality and the direction of the movement (p < 0.001). However, the changes in PF and DF ankle motion senses followed a similar trend in both groups during the three exercise modalities: static stretching increased ankle motion sense threshold (PF: 14% and 5%; DF: 19% and 11% in young and older adults, respectively), concentric contractions decreased ankle motion sense threshold (PF: -24% and -14%; DF: -19% and -21% in young and older adults, respectively), and the one-leg balance task did not significantly influence the ankle motion sense threshold (PF: -1% and -2%; DF: 6% and 1% in young and older adults, respectively)., Significance: Based on these results, static stretching should not be performed before ankle activities that require a good balance, precision, and coordination. Concentric contractions could be recommended before activities that challenge our postural stability., (Copyright © 2019 Elsevier B.V. All rights reserved.)

Introduction: This paper aimed to review the effect of physical activity and exercise in frail older persons. As the process which leads to frailty and disability can be slowed down or even completely reversed, it can be appropriate for early interventions., Methodology: A literature search was conducted in the following databases: PubMed, Cochrane, Embase, Cinahl and UpToDate. The criterion in selecting the literature was that articles were published from 2002 to 2017. From 620,043 initial hits, 25 publications were selected., Results: Physical activity and exercise in frail elderly are effective and relatively safe and may reverse frailty., Conclusion: Different exercise interventions in frail elderly persons can increase strength and power, improve balance and reduce fall incidence resulting in greater quality of life. From this perspective, physical exercise interventions should become daily routine in frail elderly persons., Competing Interests: Conflict of interest Conflicts of interest None.

Proper ankle motor control is critical for balance in the human body during functional activities such as standing, walking, and running. Different exercise modalities are often performed during the same training session where earlier activities may influence later ones. The purpose of the current study was to determine the acute effects of different exercise modalities on ankle force sense. Seventeen subjects performed four different intervention protocols (static stretching, balance task, concentric contractions, and control) in random order. Each session comprised measurements before and after the intervention protocol of the force sense of the ankle plantar flexors (PF) and dorsal flexors (DF) at 10% and 30% of maximal voluntary isometric contraction (MVC). Absolute errors (AE) were calculated separately for each force level and muscle group. An overall PF error (PF-SUM = PF at 10%MVC + PF at 30%MVC), DF error (DF-SUM = DF at 10%MVC + DF at 30%MVC) and ankle error (PF-DF-SUM = PF-SUM + DF-SUM) were also calculated. The main effect of time generally revealed that ankle force sense was significantly reduced after static stretching (PF-DF-SUM: Pre: 6.11±2.17 Nm, Post: 8.03±3.28 Nm; p < 0.05), but no significant differences were observed for the concentric contractions (PF-DF-SUM: Pre: 6.01±1.97 Nm, Post: 6.50±2.28 Nm) and the balance task (PF-DF-SUM: Pre: 5.25±1.97 Nm, Post: 5.50±1.26 Nm). The only significant interaction was observed for the PF-DF-SUM (F = 4.48, p = 0.008) due to greater error scores after stretching (+31.4%) compared to the concentric (+8.2%), balance (+4.8%), and control (-3.5%) conditions. Based on these results, static stretching should not be performed before activities that require a high ankle force sense such as balance, coordination, and precision tasks., Competing Interests: The authors have declared that no competing interests exist.

Background: As the most common form of movement, walking happens not only on flat but also on uneven surfaces, where constant loss and regaining of balance occur. The main balancing function of the ankle joint is performed by tibial muscles. When changing inclination in a frontal plane, an essential balancing function is performed by the peroneal muscles. One of the methods for improving the activity of peroneal muscles is walking with different foot placement. The objective of this study was to analyze the activity of the peroneal muscles when performing different types of walking., Methods: Sixteen healthy participants took part in this study, walking on a flat surface (NORM), on a medial incline ramp with the plantar surface of the foot fully placed on the surface (FULL), and on a medial incline ramp with elevated lateral part of the foot (LAT). We monitored the changes of EMG signals in peroneus longus (PL), peroneus brevis (PB), tibialis anterior (TA), soleus (SOL), gastrocnemius medialis (GM) and gastrocnemius lateralis (GL) muscles. We monitored kinematic parameters (gait speed, stride length, contact time, foot position). The parametric ANOVA test and a non-parametric Friedman test were used at an alpha level of 0.05., Results: This study shows that the EMG activities of peroneal muscles increases when walking on the medial incline ramp. Statistically significant EMG differences were observed in the peroneal muscles, TA and GL muscles. We observe a very high percentage of normalized EMG value of the PL muscle in LAT walking. Walking on a medial incline ramp impacts the foot position, contact time, and stride length but not the gait speed., Conclusions: Walking on a medial incline ramp could be an effective exercise to improve the neuro-muscular function of the peroneal muscles and, therefore, might be a suitable exercise for people with weakened ankle evertors., Competing Interests: This study was approved by the Ethical Committee of the Faculty of Sport, University of Ljubljana. Each participant also gave informed written consent to participate prior to entering the study.Not applicable.The authors declare that they have no competing interests.Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

Background: To analyze the safety and effects of early initiation of rehabilitation including objective measurement outcomes after lumbar spine fusion based on principles of strength training., Methods: The study recruited 27 patients, aged 45 to 70 years, who had undergone lumbar spine fusion. The method of concealed random allocation without blocking was used to form two groups. The strength training group started rehabilitation 3 weeks after surgery. Patients exercised twice weekly over 9 weeks focusing on muscle activation of lumbopelvic stabilization muscles. The control group followed a standard postoperative protocol, where no exercises were performed at that stage of rehabilitation. Functional outcomes and plain radiographs were evaluated at 3 weeks and subsequently at 3 and 18 months after the surgery., Results: No hardware loosening of failure was observed in the training group. Both groups improved their walking speed after 3 months (p < 0.01), although improvement in the training group was significantly greater than in the control group (p < 0.01). Moreover, the training group significantly improved after the training period in all isometric trunk muscles measurements (p < 0.03), standing reach height (p < 0.02), and pre-activation pattern (p < 0.05). After 18 months, no training effects were observed., Conclusions: The study showed that early initiation of a postoperative rehabilitation program based on principles of strength training is safe, 3 weeks after lumbar spine fusion, and enable earlier functional recovery than standard rehabilitation protocol., Trial Registration: The study is registered at the US National Institutes of Health ( ClinicalTrials.gov ) NCT03349580 . The date of registration: November 21, 2017 - Retrospectively registered.

García-Ramos, A, Štirn, I, Padial, P, Argüelles-Cienfuegos, J, De la Fuente, B, Strojnik, V, and Feriche, B. The maximal mechanical capabilities of leg extensors muscles to generate velocity and power improve at altitude. J Strength Cond Res 32(2): 475-481, 2018-This study aimed (a) to analyze the effect of an acute exposure to terrestrial altitude on the force-velocity relationship parameters (maximum force [F0], maximum velocity [V0], and maximum power [P0]) during a loaded squat jump (SJ), and (b) to compare unloaded SJ and countermovement jump (CMJ) performance between sea level and altitude conditions. Seventeen international swimmers were tested at sea level (295 m asl) and 7 days later at terrestrial altitude (2,320 m asl) during their first 24 hours of altitude exposure. The maximum values of force and velocity were recorded during a loaded SJ (25-100% of body weight) to determine F0, V0, and P0 parameters. Inconsequential differences between environmental conditions were found for F0 (p = 0.993, 0.02%). However, V0 (p = 0.038, 7.6%) and P0 (p = 0.004, 6.8%) were higher at altitude. Peak values of force (SJ: p = 0.420, 1.19%; CMJ: p = 0.010, 3.6%), power (SJ: p = 0.028, 3.5%; CMJ: p = 0.005, 3.82%), and take-off velocity (SJ: p = 0.071, 1.6%; CMJ: p = 0.009, 1.9%) recorded during the SJ and CMJ were also higher at altitude. These results highlight the potential effect of an acute exposure to terrestrial altitude on enhancing vertical jump performance. The increase in maximal power of the leg muscles at altitude is caused by an improvement in the theoretical maximal velocity at which lower limbs can extend with no significant changes in the theoretical maximal force.

The bilateral deficit phenomenon, characterized by a reduction in the amount of force from a single limb during maximal bilateral actions, has been shown in various movement tasks, contraction types and different populations. However, bilateral deficit appears to be an inconsistent phenomenon, with high variability in magnitude and existence, and seems to be plastic, as bilateral facilitation has also been shown to occur. Furthermore, many mechanisms underlying this phenomenon have been proposed over the years, but still remain largely unknown. The purpose of this review was to clarify and critically discuss some of the important issues relevant to bilateral deficit. The main findings of this review were: (1) bilateral deficit does not seem to be contraction-type dependent; however, it is more consistent in dynamic compared to isometric contractions; (2) postural stabilization requirements and/or ability to use counterbalances during unilateral actions seem to influence the expression of bilateral deficit to a great extent; strong evidence has been provided for higher-order neural inhibition as a possible mechanism, but requires further exploration using a lower limb model; biomechanical mechanisms, such as differences in shortening velocity between contraction modes and displacement of the force-velocity curve, seem to underlie bilateral deficit in ballistic and explosive contractions; (3) task familiarity has a large influence on bilateral deficit and thus adequate testing specificity is warranted in training/cross-sectional experiments; (4) the literature investigating the relationship between bilateral deficit and athletic performance and injury remains scarce; hence, further research in this area is required.

Purpose: Interhemispheric inhibition may play a role in the expression of bilateral deficit in force (BLD). This study investigated whether the degree of BLD is reflected in the nature of interhemispheric interaction during unilateral and bilateral contractions., Methods: Subjects divided into three groups, 'bilateral' (n = 7), 'unilateral' (n = 5) and 'control' (n = 8), performed unilateral and bilateral maximal voluntary isometric knee extensions while receiving electrical stimulation, and transcranial magnetic stimulation of the target and ipsilateral muscles. Main variables of interest included peak force for subsequent calculation of bilateral index, voluntary activation level (VAL), motor evoked potential amplitudes (MEPs) and silent period durations (SPs)., Results: BLD was noted only for the whole sample (p = 0.009), but not for any of the groups. VAL was significantly higher during bilateral compared to unilateral contractions (~97 vs. 92 %, p = 0.023), with no differences between groups. MEPs of target and ipsilateral muscles were significantly bigger during bilateral contractions (p = 0.042 and p = 0.022, respectively), with no differences between groups. No differences in SPs were observed., Conclusions: Higher values of MEPs and VAL during bilateral contractions, in conjunction with unaltered SPs, do not support the concept of inhibition related to BLD, but rather suggest the possibility of cortical facilitation. Based on the existing literature, this behavior may be specific to the lower limb musculature, but the possibility of sub-cortical or higher-order neural alterations cannot be excluded.

This study aimed to correlate, compare, and determine the reliability of force, velocity, and power values collected with a force plate (FP) and a linear transducer during loaded jumps. Twenty-three swimmers performed an incremental loading test at 25, 50, 75, and 100% of their own body weight on a FP. A linear velocity transducer (LVT) was attached to the bar to assess the peak and the mean values of force, velocity, and power. Both the peak variables (r = 0.94 - 0.99 for peak force, r = 0.83 - 0.91 for peak velocity, and r = 0.90-0.94 for peak power; p < 0.001) and the mean variables (r = 0.96-0.99 for mean force, r = 0.87-0.89 for mean velocity, and r = 0.93-0.96 for mean power; p < 0.001) were strongly correlated between both measurement tools. Differences in the shape of the force-, velocity-, and power-time curves were observed. The LVT data showed a steeper increase in these variables at the beginning of the movement, while the FP recorded larger values in the latter part. Peak values were more reliable than mean values. These results suggest that the LVT is a valid tool for the assessment of loaded squat jump.

This study evaluated the influence of an altitude training (AT) camp on swimming start time and loaded squat jump performance. To accomplish this goal, 13 international swimmers (8 women, 5 men) were allocated to both the control (Sea Level Training, SLT) and experimental conditions (AT, 2320 m above sea level) that were separated by a one year period. All tests (15 m freestyle swimming start and loaded squat jumps with additional loads of 25%, 50%, 75%, and 100% of swimmers' body weight) were performed before and after a concurrent 3-week strength and endurance training program prescribed by the national coach. Following the SLT camp, significant impairments in swimming start times to 10 (+3.1%) and 15 m (+4.0%) were observed (P < 0.05), whereas no significant changes for the same distances were detected following the AT camp (-0.89%; P > 0.05). Trivial changes in peak velocity were obtained during the loaded squat jump after both training periods (effect sizes: < 0.20). Based on these results we can conclude that a traditional training high-living high strategy concurrent training of 3 weeks does not adversely affect swimming start time and loaded squat jump performance in high level swimmers, but further studies are necessary to assess the effectiveness of power-oriented resistance training in the development of explosive actions.

This study aimed to examine the correlation of different dry land strength and power tests with swimming start performance. Twenty international level female swimmers (age 15.3 ± 1.6 years, FINA point score 709.6 ± 71.1) performed the track freestyle start. Additionally, dry land tests were conducted: a) squat (SJ) and countermovement jumps (CMJ), b) squat jumps with additional resistance equivalent to 25, 50, 75 and 100% of swimmers' body weight [BW]), and c) leg extension and leg flexion maximal voluntary isometric contractions. Correlations between dry land tests and start times at 5, 10 and 15 m were quantified through Pearson's linear correlation coefficients (r). The peak bar velocity reached during the jumps with additional resistance was the variable most correlated to swimming start performance (r = -0.57 to -0.66 at 25%BW; r = -0.57 to -0.72 at 50%BW; r = -0.59 to -0.68 at 75%BW; r = -0.50 to - 0.64 at 100%BW). A few significant correlations between the parameters of the SJ and the CMJ with times of 5 and 10 m were found, and none with the isometric variables. The peak velocity reached during jumps with external loads relative to BW was found a good indicator of swimming start performance.

Buying minimalistic shoes does not mean that you know how to use them. Salespersons are rarely competent to give adequate advice how to transition to new shoes. The same happens when someone chooses to run barefoot. So, the aim of the present experiment was to find out whether giving or not giving an explanation of the correct technique of foot placement in barefoot running and running in a minimalistic shoe influences the frequency of rear-foot strikes in natural, rear foot strikers when running barefoot or in minimalistic shoes. Thirty-nine subjects (age =34.9 ± 6.9 years, height = 174 ± 9 cm, mass = 73.1 ± 13.8 kg), randomly divided into four groups participated in this experiment. Subjects in groups 1 and 3 did not receive an explanation, while groups 2 and 4 did. Besides the difference in explanation, there was also a difference in the shoes worn during the intervention. Subjects in the groups 1 and 2 ran barefoot, while subjects in groups 3 and 4 ran in minimalistic shoes. The initial state of the foot strike patterns was measured in classic running shoes. During the intervention subjects ran according to the group they were in. 80% of the subjects in groups 1 and 3 took the most steps in a rear-foot strike pattern (Median =100) while only 21% of the subjects in groups 2 and 4 took the most steps in a rear-foot strike pattern (Median = 15.7), U = 64, z = 3.619, p (0.00) < 0.05, r = -0.58. The results show that an explanation and dem-onstration of the correct technique of foot placement in barefoot running and running in a minimalistic shoe is important when someone decides to switch from classic running shoes to minimalistic shoes or to go barefoot.

Running is performed on different natural surfaces (outdoor) and artificial surfaces (indoor). Different surface characteristics cause modification of the lower leg muscle activation pattern to adopt ankle stiffness to these characteristics. So the purpose of our investigation was to study changes of lower leg muscles activation pattern in running on different natural running surfaces. Six male and two female runners participated. The participants ran at a freely chosen velocity in trials on asphalt while in trials on gravel, and grass surfaces they were attempting to reach similar velocities as in the trials on asphalt. Muscle activation of the peroneus brevis, tibialis anterior, soleus, and gastrocnemius medialis of the right leg was recorded. Running on asphalt increased average EMG amplitude of the m. tibialis anterior in the pre-activation phase and the m. gastrocnemius medialis in the entire contact phase compared to running on grass from 0.222 ± 0.113 V to 0.276 ± 0.136 V and from 0.214 ± 0.084 V to 0.238 ± 0.088 V, respectively. The average EMG of m. peroneus brevis in pre-activation phase increased from 0.156 ± 0.026 V to 0.184 ± 0.455 V in running on grass in comparison to running on gravel. Running on different surfaces is connected with different activation patterns of lower leg muscles. Running on asphalt requires stiff ankle joints, running on gravel requires greater stability in ankle joints, while running on grass is the least demanding on lower leg muscles.

The objective of the study was to assess the use of maximum (Vmax) and final propulsive phase (FPV) bar velocity to predict jump height in the weighted jump squat. FPV was defined as the velocity reached just before bar acceleration was lower than gravity (-9.81 m·s(-2)). Vertical jump height was calculated from the take-off velocity (Vtake-off) provided by a force platform. Thirty swimmers belonging to the National Slovenian swimming team performed a jump squat incremental loading test, lifting 25%, 50%, 75% and 100% of body weight in a Smith machine. Jump performance was simultaneously monitored using an AMTI portable force platform and a linear velocity transducer attached to the barbell. Simple linear regression was used to estimate jump height from the Vmax and FPV recorded by the linear velocity transducer. Vmax (y = 16.577x - 16.384) was able to explain 93% of jump height variance with a standard error of the estimate of 1.47 cm. FPV (y = 12.828x - 6.504) was able to explain 91% of jump height variance with a standard error of the estimate of 1.66 cm. Despite that both variables resulted to be good predictors, heteroscedasticity in the differences between FPV and Vtake-off was observed (r(2) = 0.307), while the differences between Vmax and Vtake-off were homogenously distributed (r(2) = 0.071). These results suggest that Vmax is a valid tool for estimating vertical jump height in a loaded jump squat test performed in a Smith machine. Key pointsVertical jump height in the loaded jump squat can be estimated with acceptable precision from the maximum bar velocity recorded by a linear velocity transducer.The relationship between the point at which bar acceleration is less than -9.81 m·s(-2) and the real take-off is affected by the velocity of movement.Mean propulsive velocity recorded by a linear velocity transducer does not appear to be optimal to monitor ballistic exercise performance.

The objective of this study was to determine the relationship between different variables measured with a force plate during the swimming start push-off phase and start performance presented by times to 5, 10 and 15 m. Twenty-one women from the Slovenian national swimming team performed two different swim starts (freestyle and undulatory) on a portable force plate to a distance further than 15 m. Correlations between push-off variables and times to 5, 10 and 15 m were quantified through Pearson's product-moment correlation coefficient (r). The variables that significantly correlated (p < .05) to all times measured in the two starts performed were: average horizontal acceleration (freestyle: r = -0.58 to -0.71; and undulatory: r = -0.55 to -0.66), horizontal take-off velocity (freestyle: r = -0.56 to -0.69; and undulatory: r = -0.53 to -0.67) and resultant take-off velocity (freestyle: r = -0.53 to -0.65; and undulatory: r = -0.52 to -0.61). None of the variables derived from the vertical force were correlated to swimming start performance (p > .05). Based on the results of this study, we can conclude that horizontal take-off velocity and average horizontal acceleration (calculated as the average horizontal force divided by swimmer's body mass) are the variables most related to swimming start performance in experienced swimmers, and therefore could be the preferred measures to monitor swimmers' efficiency during the push-off phase.

The eggbeater kick presents an important basic technical skill in water polo. The aim of this study was to examine some different tests in order to recommend the best ones for the evaluation of the eggbeater kick. Twenty eight young male water polo players performed one test (squat jump) on land and ten tests in water: tethered swimming with legs only, using alternating and simultaneous eggbeater kicks, jumps out of water from basic and vertical (arms vertically above the head) position, water start and swimming two meters and swimming horizontally with legs only five meters with a flying start. The differences between tests were checked by executing dependent t-tests, while Pearson's correlation coefficients were calculated to evaluate the correlation between different parameters. Results showed that when performing alternate eggbeater kicks greater average forces were produced by the water polo players when compared to consecutive simultaneous eggbeater kicks. However, a short time maximal acceleration of the body in the vertical and horizontal plane was greater when the single simultaneous kick was performed. It was determined that horizontal swimming using legs only and a squat jump were less useful for the evaluation of the eggbeater kick. Therefore, the recommendation was to measure the average force of successive alternating eggbeater kicks, the height of the jump out of the water from the basic position and the water start and swim over a distance of 2 meters.

The purpose of this study was to evaluate the effect of additional light hand contact (F<1 N) in the region of the hypothenar eminence on forward movement of the center of pressure (COP) and dominant hand. Subjects sled their hypothenar eminence on a vertically-oriented pressure sensitive board while reaching forward beyond their arm length. In the two separate experiments forty nine healthy, college-aged volunteers participated in the study. Thirty subjects (mean age of 22.2±2.4 years, 6 male and 24 female) participated in the experiment on level ground and nineteen subjects (22±2.6 years, 5 male and 14 female) in the experiment on an elevated surface. The forward displacement of the COP was significantly larger (p = 0.002) when subjects were allowed to slide with the hand as compared to no contact when the activity occurred on level ground (84±10 mm and 79±11 mm, respectively), and on a one meter elevated surface (71±17 mm and 65±21 mm, respectively). The maximal forward reach of the dominant hand was significantly greater when subjects were allowed to slide with the hypothenar eminence as compared to the no contact condition on the level ground (336±35 mm and 344±38 mm, respectively, p<0.02), and on the one meter elevated surface (298±58 mm and 307±58 mm, respectively, p<0.01). This data indicate that subjects were able to use additional haptic information from the hypothenar region to bring their COP and dominant hand further forward while standing on level ground as well as on a one m elevated surface.

This study aimed to establish the differences in muscle activation between a 6-minute simulated race (all-out test) and a submaximal (blood lactate [LA] concentration 4 mmol·L(-1)) 6-minute effort (submax test) on a rowing ergometer. Eleven healthy, well-trained subjects performed the submax test followed after 1-hour rest by the all-out test. Surface electromyographic (sEMG) signal of muscles gastrocnemius medialis (GC), rectus femoris (RF), vastus lateralis (VL), biceps femoris, gluteus maximus (GM), erector spinae (ES), lower latissimus dorsi (LD&#95;lo), upper latissimus dorsi (LD&#95;up), brachioradialis (BR) and biceps brachii (BB), and other biomechanical, biochemical, and respiratory parameters were monitored during rowing. During the all-out test, the subjects covered a longer distance with larger average power output, higher stroke frequency, LA concentration, and oxygen consumption compared to the submax test (p < 0.05). During the submax test, the average rectified values (ARVs) of sEMG signal increased significantly only in the RF and LD&#95;lo muscles. During the all-out test, the ARVs of the RF, VL, and GM muscles increased (p < 0.05), whereas the MDFs of the RF, ES, and LD&#95;lo muscles decreased (p < 0.05). Compared to the submax test, the ARVs of the GC, RF, VL, LD&#95;lo, LD&#95;up, and BB muscles were significantly higher during the all-out test. However, only for the RF muscle, the all-out test resulted in a significantly lower MDF value compared to the submax test. The most involved muscles that would need special attention in training seem to be the leg and shoulder girdle extensors and arm flexors but not the trunk and hip extensors.

The aim of this study was to evaluate muscle fatigue in upper body muscles during 100-m all-out front crawl. Surface electromyogram (EMG) was collected from the pectoralis major, latissimus dorsi and triceps brachii muscles of 11 experienced swimmers. Blood lactate concentration level increased to 14.1 ± 2.9 mmol l(-1) 5 min after the swim. The velocity, stroke length and stroke rate calculated based on video analysis decreased by 15.0, 5.8 and 7.4%, respectively, during the swim. EMG amplitude of the triceps and the lower part of the latissimus muscles increased, whilst the mean power frequency (MNF) of all muscles significantly decreased by 20-25%. No significant differences in the relative MNF decrease were observed amongst the muscles; however, the differences in the rate of the MNF decrease between the lower part of the latissimus and the triceps brachii muscles were found (P < 0.05). The time of rest between the muscle activation of the two consecutive arm strokes at the end of swimming was extended (P < 0.05). It was concluded that 100-m all-out crawl induced significant fatigue with no evident differences amongst the analysed muscles.

The aim of the study was to find whether voluntary induced high- and low-frequency peripheral fatigue exhibit specific alteration in surface EMG signal (SEMG) during evoked and maximum voluntary contractions. Ten male students of physical education performed 60 s long stretch-shortening cycle (SSC) exercise with maximal intensity and 30 s long concentric (CON) exercise with maximal intensity. To verify voluntary induced peripheral fatigue, knee torques during low- (T20) and high-frequency electrical stimulation (T100) of relaxed vastus lateralis muscle (VL) were obtained. Contractile properties of the VL were measured with passive twitch and maximal voluntary knee extension test (MVC). Changes in M-waves and SEMG during MVC test were used to evaluate the differences in myoelectrical signals. T100/T20 ratio decreased by 10.9 ± 8.4 % (p < 0.01) after the SSC exercise and increased by 35.9 ± 17.5 % (p < 0.001) after the CON exercise. Significant SEMG changes were observed only after the CON exercise where peak to peak time of the M-waves increased by 9.2 ± 13.3 % (p < 0.06), SEMG amplitude during MVC increased by 32.9 ± 21.6 % (p < 0.001) and SEMG power spectrum median frequency decreased by 11.0 ± 10.5 % (p < 0.05). It is concluded that high frequency fatigue wasn't reflected in SEMG, however the SEMG changes after the CON seemed to reflect metabolic changes due to acidosis. Key pointsThe SSC exercise induced high-frequency fatigue which was not reflected in any SEMG change.The CON exercise induced dominantly low-frequency fatigue where only SEMG during MVC changedMuscle fibre membrane excitability was not changed due to low- and high-frequency fatigue but mainly reflected metabolic changes.Changes in muscle compound action potential did not follow those changes seen after electrically elicited HF and LF fatigue.

The aim of the study was to examine the presence of high-frequency fatigue (HFF) after simulated alpine slalom skiing race. Eight male alpine skiers (18.4+/-1.2 y.a., 182.3+/-3.5 cm, 80.5+/-3.4 kg) completed the study. Their average FIS points in slalom were 30.1+/-5.4. After the special skiing warm up, the following initial tests were performed: blood lactate concentration, twitch response of the relaxed VL muscle, knee torque during low- (20 Hz) and high-frequency (100 Hz) electrical stimulation of vastus lateralis muscle, and maximum, voluntary isometric knee extension torque. Then, subjects performed slalom with 45 gates, whose duration was approximately 45 s. The same test sequence, except blood lactate test was used after slalom and the measurements started exactly 60 and 180 s after slalom. Blood lactate concentration measurement started exactly 3 and 5 min after slalom. A 1x3 repeated measures; time-series design was used with one within factor of time (before 60 s, and 180 s after skiing). The average blood lactate level increased from 1.6 (0.6) pre-slalom to 7.1(1.6) mmol(-l) 15 min post-slalom (F2,14=70.1; P<0.001). Sixty seconds after slalom, twitch contraction time shortened from 78.2 (5.7) pre-slalom to 66.0 (7.2) ms post-slalom (F1.19,8.3=9.9; P<0.05). Peak twitch torque was potentiated from 21.6 (3.8) to 26.4 (5.3) Nm (F2,14=16.7; P<0.05). Slalom reduced high-frequency torque from 64.4 (35) to 58.2 (34.2) Nm 60 s post-slalom (F2,14=3.8; P<0.05), while low-frequency torque stayed virtually the same. Slalom induced HFF, which is typical of SSC exercises of maximum intensity and short duration.

The objective of this study was to determine the effect of 2 different warm-up protocols on the neuromuscular system of well-trained middle distance runners. Seven runners performed 2 different warm-up protocols, one of which included slow running, stretching, and bounding and sprinting exercises, while the other consisted of slow running and stretching only. Before and after warm-up, contractile properties of the vastus lateralis and quadriceps femoris were monitored with a single twitch test, maximal torque, and the level of muscle activation during maximal voluntary extension. The 2 types of warm-up protocols showed statistically significant differences in the increase of peak knee extension torque and muscle activation level. After warm-up 1 maximal twitch torque was increased and twitch contraction time (CT) was shortened. Both maximal torque and the level of activation were increased. Parameter changes after warm-up 2 were similar to those after warm-up 1 but not statistically significant. Sprinting and bounding as part of athletes' warm-up improve muscle activation.

Eight patients with patellar pain underwent knee proprioceptive training. The maximal knee extension torque associated with the Vastus Lateralis EMG signal increased (p 0.001 and 0.039). Although muscle balance was not improved, all the patients improved their clinical scores.

Eleven patients with recurrent dislocation of the patella were subjected to knee proprioceptive training. Patients exhibited a gain in their Lysholm and Activity scores (p 0.03 and 0.009). No patient needed operative procedure.