Žiga Kozinc

Žiga Kozinc
University of Primorska | UP · Faculty of Health Sciences (FVZ)

PhD

About

85
Publications
21,097
Reads
How we measure 'reads'
A 'read' is counted each time someone views a publication summary (such as the title, abstract, and list of authors), clicks on a figure, or views or downloads the full-text. Learn more
341
Citations
Introduction
My research interests include motor control, spinal exoskeletons for low back pain prevention, strength and conditioning (in particular, the effects of different types of resistance exercise), sports biomechanics (in particular, the force-velocity profiling in athletes, the role of bilateral deficit and the change-of-direction ability), instrumented assessments of body sway for different purposes (sports performance, risk of falling assessment etc.) and assessments of motor abilities in general.

Publications

Publications (85)
Article
In this study, we assessed pressure tolerance in 16 healthy participants at the thigh, chest, and pelvic area, using different surfaces (1 cm2, 20 cm2 and different components, used in exoskeleton design), and the effects of different padding materials. Our results showed substantial variability in pressure tolerance among the participants, as well...
Article
Traditionally, a larger difference between countermovement (CMJ) and squat jump (SJ) was seen as beneficial, as it reflects the ability to utilize the stretch-shortening cycle. However, strong arguments have been made that this might not always be the case, as larger differences between the jumps could also suggest higher muscle-tendon slack, or po...
Article
Full-text available
The purpose of this study was to assess the association between bilateral deficit (BLD) in countermovement jump and change of direction (CoD) performance. Therefore, 165 young basketball players (60 females) and 95 young tennis players (39 females) performed two different CoD tasks (90° and 180° turns) and bilateral and unilateral countermovement j...
Article
Full-text available
When humans perform isometric ballistic contractions of different intensities, a strong linear relationship is observed between peak force and peak rate of force development. The slope of this relationship, termed the rate of force development scaling factor (RFD-SF), has been proposed as a measure of neuromuscular quickness of submaximal contracti...
Article
Full-text available
It is well-accepted that at least a certain amount of resistance exercise (RE) is recommended for most endurance athletes. In this review, we aim to summarize the evidence regarding the effects of RE on running economy, running biomechanics, and running-related injury risk in endurance runners. The evidence robustly shows that lower limb RE is effe...
Article
An abundance of information can be found in the scientific literature regarding the bilateral deficit (BLD) in different contraction types, including its possible underlying mechanisms. On the other hand, studies on the relationship between BLD and athletic performance have only begun to emerge in recent years. The purpose of this review article is...
Article
Full-text available
The force-velocity (F-v) relationship has been proposed as a biomechanical characteristic to comprehensively evaluate neuromuscular capabilities within different tasks such as vertical jumping, sprinting and bench pressing. F-v relationship during flywheel (FW) squats was already validated, however, it was never compared to F-v profile of vertical...
Article
[Main text in Slovene] Aging is a complex multidimensional process that manifests differently in each individual. The process of ageing is characterized by many biological changes, which are reflected in weight loss, loss of muscle strength and power, loss of movement functionality and cognitive decline. These changes reduce physiological resilienc...
Article
Ultrasound imaging is widely used in scientific research, as well as in the clinical practice, to assess morphological and mechanical properties of muscles and tendons. It also has applications in elite sport, for assessing training adaptations and for the identification of structural anomalies. Shear wave elastography is being increasingly used in...
Article
Full-text available
The aim of our study was to assess eccentric-exercise-induced changes in passive knee joint torque, passive knee joint stiffness and shear modulus at of the hamstring muscles. We hypothesized that eccentric exercise would elicit an increase in all outcomes. Fourteen healthy volunteers (age = 25.5±4.7 years) performed eccentric exercise protocol. Be...
Article
Full-text available
Background The ability to perform a quick and rapid change of direction (CoD) is an important determinant of success in a variety of sports. Previous studies have already highlighted that eccentric strength is a dominant predictor of CoD. However, these studies evaluated eccentric strength through a limited number of outcome measures and used small...
Conference Paper
The purpose of this paper is to present the findings of a large literature review, conducted to obtain reference data for isometric knee extension and flexion strength through meta-analysis. Our analysis included 411 studies, with a total of 13893 participants (8788 adults from the general population, 3279 older adults, 1826 athletes and 359 childr...
Conference Paper
Introduction: Evaluation of the force-velocity-power (FVP) relationship has recently been established as a potentially useful method for monitoring athletes’ performance and designing training programs. The existing literature is ambiguous regarding the relationship between the profile F-V-P in single-joint and multi-joint movements. The main objec...
Article
Full-text available
The effects of eccentric exercise (ECC) in older adults have received limited scientific attention, considering the ample evidence for its effectiveness in general and athletic populations. The purpose of this paper is to review the effects of ECC exercise modalities versus traditional or concentric (CON) exercise on muscle strength, body compositi...
Article
Full-text available
Prolonged trunk flexion is known to affect passive and active stabilization of the trunk. Previous studies have evaluated changes in spinal range of motion, muscle activity and reflex behavior induced by prolonged trunk flexion, whereas the effect on sitting postural control is vastly underexplored. In this study, we compared the effects of support...
Article
Full-text available
Jumping performance is one of the key components of volleyball game, thus evaluating jumping ability through different biomechanical variables offers opportunity for performance optimization. The aim of this study was to assess the associations between reactive strength index (RSI), reactive strength index modified (RSImod) and approach jump perfor...
Article
Full-text available
This study aimed to determine if there is a difference in postural stability in highly trained adolescents and young adult athletes regarding sex and sport. The participants were young athletes (n = 464) from seven different sports. We considered the center of pressure (CoP) velocity (total, anterior–posterior (AP) and medial–lateral (ML)), CoP amp...
Article
Full-text available
This study aimed to determine the interrater and intrarater reliability of EasyForce dynamometer for assessing shoulder, knee, and hip muscle strength in healthy young adults. Shoulder, knee, and hip maximal isometric strength were measured using the EasyForce in healthy adults (11 women and 12 men). Three repetitions of shoulder internal rotation,...
Article
Full-text available
We assessed the association between bilateral deficit (BLD) in countermovement jump (CMJ) and change of direction (CoD) performance, CoD deficit, linear sprinting and approach jump tasks. The participants (47 young volleyball players; age: 20.8 ± 3.8 years) performed bilateral and single-leg CMJs, modified T-test, 505 CoD test, 25-m sprints (with 5...
Article
Full-text available
Traditional neuromuscular tests (e.g., jumping and sprinting tasks) are useful to assess athletic performance, but the basic outcomes (e.g., jump height, sprint time) offer only a limited amount of information, warranting a more detailed approach to performance testing. With a more analytical approach and biomechanical testing, neuromuscular functi...
Article
Full-text available
The purpose of this study was twofold: (a) to compare postural control between a group of young female gymnasts (n = 15; age: 11.2 ± 1.9 years) and non-trained peers (n = 15; age: 10.9 ± 2.0 years), and (b) to investigate the effect of an 8-week whole body exercise intervention program on postural control in young female gymnasts. Postural control...
Article
The aim of this study was to investigate the reliability of running biomechanics assessment with a wearable commercial sensor (RunScribeTM). Participants performed multiple 200-m runs over sand, grass and asphalt ground at the estimated 5-km tempo, with an additional trial with 21-km tempo at the asphalt. Intra-session reliability was excellent for...
Article
This study aimed to assess intra- and inter-visit reliability of a novel EasyForce dynamometer for assessment of maximal strength in knee extension and flexion, and hip abduction and adduction tasks. Young healthy participants (n = 50; 25 males, 25 females; age: 23.4 ± 2.1 years) were measured for maximal joint torque with EasyForce dynamometer and...
Article
Change of direction (CoD) ability is critical for the success of athletes in many sports. The purpose of this study was to perform a principal component analysis using 9 CoD tests in order to reveal possible subcomponents of CoD ability, which could aid practitioners in test selection. Male and female kinesiology students (n = 76) performed all CoD...
Article
Full-text available
Musculoskeletal disorders are the most common work-related health problems. As low back disorders (LBD) are the most problematic, the aim of this study was to provide an in-depth analysis of the nationwide data on sick leaves due to work-related LBDs among workers in Slovenia in 2015–2019 by gender, age and various economic activities (NACE Rev 2 c...
Article
Full-text available
Patients after joint arthroplasty tend to be less physically active; however, studies measuring objective physical activity (PA) and sedentary behavior (SB) in these patients provide conflicting results. The aim of this meta-analysis was to assess objectively measured PA, SB and performance at periods up to and greater than 12 months after lower li...
Article
Šport : revija za teoretična in praktična vprašanja športa (69;2: 109-114). [Main text in Slovene] The force-velocity (FV) profiling has recently been proposed as a tool to identify the neuromuscular capabilities of athletes and to optimized the training based on the obtained results. The FV relationship allows the identification of the mechanical...
Article
This study sought to investigate the inter-relationship between different vertical and horizontal variants of reactive strength index (RSI) and change of direction performance. Thirty-one male volleyball players (age: 22.4 ± 3.9 years), performed bilateral drop jumps (DJ), bilateral and unilateral countermovement jumps (CMJ), and triple hops for di...
Article
Full-text available
Spinal exoskeletons have been suggested as an approach for the prevention and rehabilitation of occupational low back pain (LBP). While the state-of-the-art exoskeletons were shown to substantially unload the back, user acceptance is still limited. Perceived discomfort and restriction of freedom of movement are commonly reported. In this pilot stud...
Article
Full-text available
In this study, 90 (51 males, 39 females) tennis players performed single-leg quiet stance and single-leg landing tasks. For the static standing task, center-of pressure (CoP) velocities, amplitudes, frequency and area were calculated. For the landing tasks, time to stabilization as well as dynamic postural stability index were considered. The analy...
Article
Full-text available
BACKGROUND AND STUDY AIM: There is a lack of the test for evaluation sport-specific movements in karate. The aim of this study was empirical argumentation about reliability of karate-specific test (KSAT) and its associations with T-test and change of direction (CoD). MATERIAL AND METHODS: The decomposition of the project goal into research tasks w...
Article
Full-text available
The difference between squat jump (SJ) and countermovement jump (CMJ), termed eccentric utilization ratio (EUR), is frequently suggested as an outcome that can be used in athletic training design. Unlike performance in SJ and CMJ, which is associated with sports performance, the association between EUR and sports performance is almost unexplored. T...
Article
Background Postural sway during quiet standing has been shown as a useful task to assess risk of falling in older adults. While the risk of falling is consistently reported to be higher in older females than males, the sex-related differences in postural sway are not consistent across the studies. Research question What are the effects of age and...
Article
Full-text available
The force-velocity (FV) relationship allows the identification of the mechanical capabilities of musculoskeletal system to produce force, power and velocity. The aim of this study was to assess the associations of the mechanical variables derived from the force-velocity (FV) relationship with approach jump, linear sprint and change of direction (Co...
Article
Full-text available
The purpose of this pilot study was to investigate the effects of change-of-direction (CoD) angle (90° vs. 180°) and the inclusion of acceleration approach on total task time, CoD deficit, and agreement regarding inter-limb asymmetry direction across CoD tasks. The sample included 13 young male handball players (age: 22.4 ± 3.2 years). The CoD task...
Article
Full-text available
Single-joint isometric and isokinetic knee strength assessment plays an important role in strength and conditioning, physical therapy and rehabilitation. The literature, however, lacks absolute reference values. We systematically reviewed the available studies that assessed isometric knee strength. Two scientific databases (PubMed and PEDro) were s...
Presentation
Introduction. Osteoarthritis (OA) is the most common degenerative musculoskeletal disorder affecting mostly older adults. It causes joint pain, limits functional ability, decreases physical activity levels, and leads to increased sedentary behavior. To restore function and maintain a healthy lifestyle, hip and knee arthroplasty are being considered...
Article
Introduction Jumping ability is one of the most important physical qualities in military personnel. Previous training intervention studies have shown equivocal effects on jumping ability. In this study, we assessed the effect of a 12-week resistance exercise programme on countermovement jump (CMJ) performance with and without military equipment. M...
Article
Full-text available
Change-of-direction (CoD) ability is an important determinant of athletic performance. Muscle strength is among the most important determinants of CoD ability. However, previous studies investigating the relationship between CoD ability and muscle strength focused mostly on flexor and extensor muscle groups, or used multi-joint exercises, such as j...
Article
Full-text available
Neuromuscular fatigue is known to impair balance ability, which is reflected in increased postural sway during quiet standing tasks. Recently, quantifying transient characteristics of postural sway has been suggested as an approach to obtain additional information regarding postural control. However, this approach is currently vastly unexplored. Th...
Thesis
The purpose of this doctoral thesis is to present the results of three studies related to the assessment of the effects of spinal exoskeletons on functional performance and subjective responses. The aim of the first study was to verify the reliability of a battery of tests, which consists of 12 functional tasks and subjective assessments. In the se...
Article
Musculoskeletal disorders are an important cause of absenteeism and long-term absence from work. Musculoskeletal disorders are partly caused by aging, but mainly by inappropriate working environments, insufficient physical activity and prolonged sitting. The COVID-19 epidemic has affected all of these aspects: it increased the amount of teleworking...
Article
Full-text available
We examined the relationships between heights of different vertical jumps and isometric single-joint strength characteristics of ankle, knee, hip, and trunk joints in young male soccer players (n = 117). The highest peak torque and rate of torque development (RTD) outcomes were in low to moderate correlation with jump heights (r = 0.25–0.50). The c...
Article
Full-text available
The aim of this study was to determine the relationship between strength of ankle plantar and dorsal flexors and range of motion (RoM), and body sway variables during single-leg quiet stance, in highly trained athletes. The participants for this study were young athletes from 9 disciplines (n = 655). Center of pressure (CoP) velocity, amplitude, an...
Conference Paper
Introduction: Current evidence suggests that impaired balance and lack of strength/power of the lower extremities are among the most important risk factors for fall-related injuries in all stages of life. Thus, effective approaches to counteracting these two factors are much desired. Methods: With a systematic review and meta-analysis of the litera...
Article
Full-text available
Objective: Previous research suggests that muscle strength exercise is the most effective rehabilitation methods in patients with patellofemoral pain (PFP). This systematic review with meta-analysis compared the effects of Hip&Knee, Hip-only and Knee-only exercise programs on pain relief, muscle strength, and functional performance in patients wit...
Article
This study aimed to assess the within- and between-session reliability of the KiSprint system for determining force-velocity-power (FVP) profiling during sprint running. Thirty (23 males, 7 females; 18.7 ± 2.6 years;) young high-level sprinters performed maximal effort sprints in two sessions separated by one week. Split times (5, 10, 20 and 30 m),...
Chapter
Spinal exoskeletons have recently emerged as a potential tool to prevent and treat low back pain (LBP) in workers that are involved in heavy load handing and other demanding jobs. However, the widespread use of these devices is still limited. Notably, discomfort and hindrance of movement is often reported by the end-users. Therefore, there is an in...
Article
Background The role of the measurements of postural stability in the context of screening for ankle sprain risk is still equivocal. Transient characteristics of body sway have been suggested as an alternative or an improvement to traditional whole-trial analyses. Research question Are transient characteristics of body sway sensitive to the history...
Article
Full-text available
An abundance of literature has investigated the association between low back pain (LBP) and physical ability or function. It has been shown that LBP patients display reduced range of motion , decreased balance ability, impaired proprioception, and lower strength compared to asymptomatic persons. The aim of this study was to investigate the differen...
Article
Full-text available
Tai Chi has been shown to elicit numerous positive effects on health and well-being. In this study, we examined reactive postural control after sudden unloading horizontal perturbations, which resembled situations encountered during Tai Chi. The study involved 20 participants, 10 in the Tai Chi group (age: 37.4 ± 7.8 years), who had been regularly...
Article
Full-text available
Purpose Low back pain (LBP) remains a major worldwide healthcare issue. Recently, spinal exoskeletons were proposed as a potentially useful solution for LBP prevention and vocational reintegration for people who perform heavy load lifting, repetitive movements or work in prolonged static postures. The purpose of this study was to investigate how pa...
Article
This study explored transient characteristics of body sway during single-leg quiet stance in young ballet dancers (n = 41) and young healthy adults (n = 58). We compared the groups in terms of center of pressure (CoP) parameters (CoP velocity and amplitude, averaged across the duration of the 30-s trial), and the transient characteristics of the co...
Article
Full-text available
Instrumented assessments of quiet-stance postural control typically involve recording and analyzing of body sway signal, most often the center of pressure (CoP) movement. It has been recently suggested that transient characteristics of body sway may offer additional information regarding postural control. In this study we explored the relationship...
Conference Paper
Spinal exoskeletons have recently emerged as a potential tool to prevent and treat low back pain (LBP) in workers that are involved in heavy load handing and other demanding jobs. However, the widespread use of these devices is still limited. Notably, discomfort and hindrance of movement is often reported by the end-users. Therefore, there is an in...
Article
[Main text in Slovene]. Iliotibial band syndrome (ITBS) is one of the most common running-related injuries. The purpose of this systematic review with meta-analysis was to investigate the risk factors for occurrence of ITBS. After systematic search of the PubMed database, 20 case-controland 3 prospective studies that reported differences between ru...
Article
In this study, we investigated the prevalence of inter-limb asymmetries in young volleyball players and assessed the differences in the outcomes of different strength and power tests. The study sample comprised of 54 young volleyball players (25 males). Both limbs were tested for single-leg jumping for distance (forward and lateral single jump and...
Article
Full-text available
Rate of force/torque development scaling factor (RFD-SF/RTD-SF) has been used as a tool for assessing neuromuscular quickness. The aim was to investigate strength capacities of two major shooting muscle groups and their relationship to basketball shooting performance, and to compare the RFD-SF as well as shooting performance between junior and seni...
Article
Background Recently, the rate of torque development scaling factor (RTD-SF) has been proposed as a useful tool that could contribute to a more comprehensive insight into muscular capacity. While lower RTD-SF is associated with ageing and certain neuromuscular diseases, it remains unknown whether this novel measure is associated with the postural co...
Article
Full-text available
Background: The linear relationship between muscle torque and rate of torque rise/relaxation during rapid muscle contractions has been recently introduced as a novel measure of muscle quickness, termed rate of torque development/relaxation scaling factor (RTD-SF/RTR-SF). Because the standard assessment protocol includes potentially painful muscle...
Article
Full-text available
Abstract Recently, the two-point method of force–velocity (F–V) profiling of multi-joint human movements has been introduced and validated. In this study, we investigated the validity of estimating the jumping F–V profile using only bodyweight jump and isometric maximal voluntary contraction (MVC) task. Participants (n = 30) performed 3 repetitions...
Article
Full-text available
With this systematic review, we explored whether resistance exercise (RE) could be used to improve balance in addition to muscular strength and power. Scientific databases were searched for randomized controlled trials that investigated the effects of RE on the performance of various balance tests. Studies were considered if they involved healthy p...
Article
We explored the associations between force-velocity-power (FVP) profiles and inter-limb asymmetries in FVP profiles obtained during unilateral jumping and single-leg isokinetic knee extension and flexion tasks. Thirty (13 senior and 17 junior) basketball players performed unilateral jumps with different levels of unloading (0–40% body mass) and iso...
Article
Full-text available
It has been shown that resistance exercise (RT) is one of the most effective approaches to counteract the physical and functional changes associated with aging. This systematic review with meta-analysis compared the effects of RT, whole-body vibration (WBV), and electrical muscle stimulation (EMS) on muscle strength, body composition, and functiona...
Article
Full-text available
Falls are a major cause of injury and morbidity in older adults. To reduce the incidence of falls, a systematic assessment of the risk of falling is of paramount importance. The purpose of this systematic review was to provide a comprehensive comparison of the diagnostic balance tests used to predict falls and for distinguishing older adults with a...
Article
Recently, several spinal exoskeletons were developed with the aim to assist occupational tasks such as load-handling and work in prolonged static postures. While the biomechanical effects of such devices has been well investigated, only limited feedback to the developers is usually provided regarding the subjective perceptions of the end-users. The...
Article
Full-text available
Purpose The purpose of the present study was to investigate the influence of strength outcome (maximal voluntary contraction (MVC) torque vs. rate of torque development (RTD)), motor task (unilateral vs. bilateral) and muscle group (knee extensors vs. flexors) on the magnitude of bilateral deficits and inter-limb asymmetries in a large heterogeneou...
Article
Due to its accessibility, low cost and well-known health benefits, running has become one of the most popular sports in the world. With its increasing popularity the number of running related injuries, especially in the lower extremities have increased. The most common are plantar fasciitis, Achilles tendinopathy, patellofemoral pain syndrome, ilio...