Johannes Zwerver

University of Groningen | RUG · Department of Sports Medicine

Objective: To systematically describe the next relevant aspects of tendotonometry in (1) its validity and reliability, (2) differences between populations, (3) the effect of interventions, and (4) differences between healthy and symptomatic Achilles tendon (AT) and patellar tendon (PT). Data Sources: Three online databases (PubMed, Embase, and E...

This observational study aimed to evaluate the intra- and inter-operator reliability of a digital palpation device in measuring compressive stiffness of the patellar tendon at different knee angles in talent and elite volleyball players. Second aim was to examine differences in reliability when measuring at different knee angles, between dominant a...

Background : To better understand physical activity behavior and its health benefits in people living with health conditions, we studied people with and without 20 different self-reported health conditions with regard to (1) their physical activity levels, (2) factors correlated with these physical activity levels, and (3) the association between p...

Abstract Background Biofeedback may alter the biomechanics of lower extremities in patients with chronic ankle instability (CAI). We aimed to systematically review the literature on the effect of gait-training and biofeedback on biomechanical parameters in individuals with CAI and conduct a meta-analysis. Methods We searched four databases includi...

Background Patellar tendinopathy (PT) is a common problem in jumping athletes. Management can be challenging and treatment outcome is not always successful. In combination with tendon loading exercises, hydrolyzed collagen/vitamin C supplementation appears to have a promising effect on the recovery of tendinopathy. The aim of this study is to evalu...

Objectives Abdominal complaints (AC) during exercise are a common problem in runners. Nutrition is known to play a role in exercise-related AC, but information on the role of habitual dietary intake is limited. We assessed the prevalence of AC in a large cohort of runners, and investigated its association with potential risk factors, with a particu...

Objectives Lower limb tendinopathy (LLT) is highly prevalent in runners. Treatment can be challenging, and knowledge of risk factors may be valuable to develop preventive or treatment interventions for LLT. The aims of this study were (1) to assess the prevalence of three common LLTs (Achilles tendinopathy (AT), patellar tendinopathy and plantar fa...

Background A healthy lifestyle is indispensable for the prevention of noncommunicable diseases. However, lifestyle medicine is hampered by time constraints and competing priorities of treating physicians. A dedicated lifestyle front office (LFO) in secondary/tertiary care may provide an important contribution to optimize patient-centred lifestyle c...

Background Both physical and psychological readiness are important for a successful return to sport (RTS) and secondary prevention. The ACL-Return to Sport after Injury (ACL-RSI) and Injury-Psychological Readiness to Return to Sport (I-PRRS) scales were developed to assess psychological factors associated with RTS. Validity and reliability have bee...

Objective: To gain insight into the changes in psychological factors during rehabilitation after Achilles tendon rupture (ATR) and to explore the association between psychological factors during rehabilitation and functional outcome 12 months after ATR. Methods: Fifty patients clinically diagnosed with ATR were invited to visit the hospital 3, 6...

Objective To provide a comprehensive, evidence-based overview of the risk factors, prevention, diagnosis, imaging, treatment and prognosis for Achilles tendinopathy. To make clinical recommendations for healthcare practitioners and patients. Design Comprehensive multidisciplinary guideline process funded by the Quality Foundation of the Dutch Fede...

Objective to examine psychological factors during rehabilitation of patients with Achilles or patellar tendinopathy as well as the association between psychological factors and tendinopathy severity, sport participation, and satisfaction with activity level and tendon function. Design cross-sectional study. Setting: online survey platform. Partic...

Knowledge about prevalence and etiology of running-related injuries (RRIs) is important to design effective RRI prevention programs. Mental aspects and sleep quality seem to be important potential risk factors, yet their association with RRIs needs to be elucidated. The aims of this study are to investigate the epidemiology of RRIs in recreational...

Atypical rearfoot in/eversion may be an important risk factor for running-related injuries. Prominent interventions for atypical rearfoot eversion include foot orthoses, footwear, and taping but a modification derived from gait retraining to correct atypical rearfoot in/eversion is lacking. We aimed to investigate changes in rearfoot in/eversion, s...

Aims Advanced glycation endproducts (AGEs) are sugar modified adducts which arise during non-enzymatic glycoxidative stress. These compounds may become systemically elevated in disease states, and accumulate in tissue, especially on long-lived proteins. AGEs have been implicated in various acute, and chronic diseases, stressing the need for reliabl...

Introduction Atypical rearfoot eversion is an important kinematic risk factor in running-related injuries. Prominent interventions for atypical rearfoot eversion include foot orthoses, footwear, and taping, yet a running gait retraining is lacking. Therefore, the aim was to investigate the effects of changing mediolateral center of pressure (COP) o...

Objective To compare the effectiveness of progressive tendon-loading exercises (PTLE) with eccentric exercise therapy (EET) in patients with patellar tendinopathy (PT). Methods In a stratified, investigator-blinded, block-randomised trial, 76 patients with clinically diagnosed and ultrasound-confirmed PT were randomly assigned in a 1:1 ratio to re...

Objective: Physical activity (PA) has substantial health benefits and is important in combatting chronic diseases, which have been associated with elevated levels of advanced glycation endproducts (AGEs). AGEs play a role in the ageing process, and an association between PA and AGEs has been reported. We aimed to investigate the relationship betwe...

PurposeAim of this study was to evaluate the responsiveness of the Dutch version of the Achilles tendon Total Rupture Score (ATRS-NL).Methods Patients (N = 47) completed the ATRS-NL at 3 and 6 months after Achilles tendon rupture (ATR). Additionally, they filled out the Euroqol-5D-5L (EQ-5D-5L) and Global Rating of Change Score (GRoC). Effect sizes...

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Objective: To investigate the validity and reliability of a smartphone application for selected lower-limb kinematics during treadmill running. Design: Validity and reliability study. Setting: Biomechanics laboratory. Participants: Twenty healthy female runners. Main outcome measure(s): Sagittal-plane hip, knee, and ankle angle and rearfoo...

The objective was to evaluate the effectiveness of an exercise-based warm-up programme ("VolleyVeilig") on the one-season occurrence of musculoskeletal injuries among recreational adult volleyball players. A prospective randomised controlled trial was conducted over the 2017-2018 volleyball season. Recreational adult volleyball players were allocat...

Context Several studies have been conducted to better understand the effect of load on the Achilles tendon structure. However, the effect of a high cumulative load consisting of repetitive cyclic movements, such as those that occur during the running of a marathon, on Achilles tendon structure is not yet clear. Clinicians, coaches, and athletes wil...

Background Knowledge about prevalence and etiology of running-related injuries (RRIs) is important to tailor an effective RRI prevention program. We aimed to investigate the prevalence and etiology of RRIs in Iranian recreational runners. Methods An internet-based self-developed questionnaire was sent to recreational runners recruited through socia...

Background: The absence of any agreed-upon tendon health-related domains hampers advances in clinical tendinopathy research. This void means that researchers report a very wide range of outcome measures inconsistently. As a result, substantial synthesis/meta-analysis of tendon research findings is almost futile despite researchers publishing busil...

We aimed to establish consensus for reporting recommendations relating to participant characteristics in tendon research. A scoping literature review of tendinopathy studies (Achilles, patellar, hamstring, gluteal and elbow) was followed by an online survey and face-to-face consensus meeting with expert healthcare professionals (HCPs) at the Intern...

The ACL-Return to Sport after Injury (ACL-RSI) and Injury-Psychological Readiness to Return to Sport (I-PRRS) scales were developed to assess psychological factors associated with return to sports. Validity and reliability have been determined. The aim of this study was to investigate the responsiveness of the Dutch ACL-RSI and I-PRRS. Seventy pati...

Long-distance open-water swimming is a swimming discipline which takes place in outdoor bodies of water, such as open oceans, lakes and rivers. The activity has grown in popularity. This case report describes the attempt of an Olympic Champion (Maarten van der Weijden) to swim 200 km along a route taking him to eleven Frisian cities. We describe th...

Purpose Ultrasound tissue characterization (UTC) is used in research and clinical practice to quantify tendon structure of the patellar tendon. This is the first study to investigate the inter‐ and intra‐rater reliability for UTC of the patellar tendon on a large scale. Method Fifty participants (25 patellar tendinopathy, 25 asymptomatic) were rec...

Objective: To determine the role of ultrasound tissue characterization (UTC) in predicting, diagnosing, and monitoring tendon structure and/or tendinopathy. In addition, this study aims to provide recommendations for standardized methodology of UTC administration and analysis. Data source: The PubMed, Embase, and Web of Science databases were se...

The purpose of this study was to investigate the relation between external and internal load and the response of the patellar tendon structure assessed with Ultrasound Tissue Characterization (UTC) in elite male volleyball players during preseason. Eighteen players were followed over seven weeks, measuring four load parameters during every training...

Purpose Changes in tendon structure are commonly seen in patients with unilateral achilles (AT) or patellar (PT) tendinopathy but might also be present on the asymptomatic side, indicating a higher risk for developing symptoms. The aim of this study is to compare tendon structure of the symptomatic side with the asymptomatic side in AT and PT patie...

Introduction More than half a million athletes were enrolled in a marathon run during the last years. During running the Achilles tendon is submitted to high loads, and multiple tensile strain cycles. There are no studies investigating the effect of a marathon in the structure of the Achilles tendon. Thus, the aim of this study was to investigate t...

Introduction: Abnormal kinematics have been implicated as one of the major risk factors for lower limb tendinopathy (LLT). Objective: To systematically review evidence for kinematic risk factors for LLT in runners. Methods: Individual electronic searches in PubMed, EMBASE and Web of Science were conducted. Two reviewers screened studies to identi...

Background Achilles tendon rupture (ATR) is a common sports injury, with a rising incidence and significant impairments. Due to the lack of treatment guidelines, there is no consensus about diagnostic methods, primary treatment (non-surgical or surgical) and rehabilitation. It is hypothesized that this lack of consensus and guidelines leads to sub-...

The Injury Psychological Readiness to Return to Sport (I-PRRS) scale measures the psychological readiness of injured athletes to resume sports participation. The aim of this study was to translate and culturally adapt the I-PRRS scale into Dutch (I-PRRS-NL) and assess its validity, reliability, and stability in patients after anterior cruciate liga...

Tendinopathieën van de achilles- en patellapees als gevolg van fysieke (over)belasting komen relatief veel voor binnen de werkende en sportende populatie (Tabel 1). Door overbelasting ontstaan er, na een initiële reactieve tendinopathie met ontstekingcomponent (‘tendinitis’) geleidelijk aan structurele veranderingen in de pees en is er uiteindelijk...

Objectives: The aim of this study was to investigate the effects of a 4-week in-season exercise program of isometric or isotonic exercises on tendon structure and dimensions as quantified by Ultrasound Tissue Characterization (UTC). Design: Randomized clinical trial. Volleyball and basketball players (16-31 years, n=29) with clinically diagnosed...

Purpose: This study aimed to describe and analyse usual care of Achilles tendon ruptures (ATRs) by orthopaedic surgeons and trauma surgeons in the Netherlands. Methods: A nationwide online survey of ATR management was sent to all consultant orthopaedic and trauma surgeons in the Netherlands, requesting participation of those involved in ATR mana...

Objectives: To observe the changes in Achilles tendon structure in novice runners, with loading prescriptions of 100% body weight compared to 20% body weight. Design: Randomised crossover. Methods: Twenty novice runners participated in two separate running bouts spaced 14days apart, one of high load at 100% body weight, and one of low load at...

Objective: To determine the association between clinical and imaging outcomes after therapeutic loading exercise in Achilles tendinopathy (AT) and patellar tendinopathy (PT) populations at both short- and long-term follow-up. Data Sources: The PUBMED and EMBASE databases were searched (up to June 2017) to identify articles that meet the inclusion c...

Objective: To determine the association between clinical and imaging outcomes after therapeutic loading exercise in Achilles tendinopathy (AT) and patellar tendinopathy (PT) populations at both short- and long-term follow-up. Data sources: The PUBMED and EMBASE databases were searched (up to June 2017) to identify articles that meet the inclusio...

Objective: The aim of this study was to define the minimum amount of exercise per week ('current exposure') and the total amount of exercise ('lifetime exposure') needed to lead to the electrocardiographic changes fitting athlete's heart. Methods: All the pre-participation screenings (including electrocardiograms (ECGs)) from collegiate athletes...

Although injury surveillance in athletics is routinely conducted, discipline-specific Achilles and patellar tendinopathy prevalence remains unknown. The purpose of this study was to explore discipline-specific tendinopathy prevalence and identify whether injury-specific risk factors differed in athletes. Elite athletes were recruited and provided i...

Objective: Currently, no treatments exist for patellar tendinopathy (PT) that guarantee quick and full recovery. Our objective was to assess which treatment option provides the best chance of clinical improvement and to assess the influence of patient and injury characteristics on the clinical effect of these treatments. Design: A secondary anal...

Background: A scientific research project has started in the Netherlands with the aim of developing and implementing an evidence-based intervention to prevent the occurrence of musculoskeletal injuries among young and adult recreational volleyball players. This article describes (i) the systematic development of the intervention; and (ii) the asse...

Background: Extracorporeal shockwave therapy (ESWT) seems to be an effective treatment for plantar fasciitis (PF) and is assumed to be safe. No systematic reviews have been published that specifically studied the complications and side effects of ESWT in treating PF. Aim of this systematic review is therefore to evaluate the complications and side...

Objective: To determine the role of imaging in the diagnosis and monitoring of the Achilles tendon rupture (ATR). Study design: Systematic review. Data sources: PubMed and EMBASE in November 2016. Eligibility criteria: Clinical studies providing information on the methods and role of imaging in the diagnosis and monitoring of the ATR were in...

Background Both acute and overuse injuries are common among recreational volleyball players, especially finger/wrist, ankle, shoulder and knee injuries. Consequently, an intervention (‘VolleyVeilig’) was developed to prevent or reduce the occurrence of finger/wrist, shoulder, knee and ankle injuries among recreational volleyball players. This artic...

Objective: This study aimed to compare the immediate analgesic effects of 2 resistance programs in in-season athletes with patellar tendinopathy (PT). Resistance training is noninvasive, a principle stimulus for corticospinal and neuromuscular adaptation, and may be analgesic. Design: Within-season randomized clinical trial. Data analysis was co...

Greater insight into sports and work performance of athletes with patellar tendinopathy (PT) will help establish the severity of this common overuse injury. Primary aim of this study is to investigate the impact of PT on sports and work performance. Seventy seven active athletes with PT (50 males; age 28.1 ± 8.2 years; Victorian Institute of Sports...

Currently, there is no overview of the incidence and (volleyball-specific) risk factors of musculoskeletal injuries among volleyball players, nor any insight into the effect of preventive measures on the incidence of injuries in volleyball. This study aimed to review systematically the scientific evidence on the incidence, prevalence, aetiology and...

Objectives: The primary aim of this study was to investigate the effect of a patellar strap on the proprioception of the symptomatic leg in PT. Secondary aims were to investigate a possible difference in effectiveness between athletes with high and low proprioceptive acuity, and whether predictors of effectiveness could be found. Design: Randomi...

Background Patellar tendinopathy is a common overuse injury in jumping sports, with higher prevalence in volleyball players. Different risk factors are associated with patellar tendon problems, including training load. Despite different treatment options, rates of chronicity and recurrence are high. Therefore, the high prevalence and the challengin...

Objectives Many athletes with patellar tendinopathy participate in sports with symptoms during or after activities. Current treatments do not decrease pain in-season; eccentric exercises in-season result in an increase in pain. This study examined if isometric and isotonic exercises relieved pain in competing athletes with patellar tendinopathy. D...

Shockwave treatments are commonly used in the management of tendon injuries and there is increasing evidence for its clinical effectiveness. There is a paucity of fundamental (in vivo) studies investigating the biological action of shockwave therapy. Destruction of calcifications, pain relief and mechanotransduction-initiated tissue regeneration an...

Exercise is crucial in the management of diabetes mellitus and its associated complications. However, individuals with diabetes have a heightened risk of musculoskeletal problems, including tendon pathologies. Diabetes has a significant impact on the function of tendons due to the accumulation of advanced glycation end-products in the load-bearing...

Objective: To evaluate the effectiveness of a combined treatment of focused shockwave therapy (ESWT) and eccentric training compared with sham-shockwave therapy (placebo) and eccentric training in participants with patellar tendinopathy (PT) after 24 weeks. Design: Randomized controlled trial. Setting: Sports medicine departments of a universi...

Background Lower extremity tendinopathy is a common sports injury, but it can also affect non-athletes. Because tendinopathy is difficult to treat and has negative effects on the ability to work and quality of life, development of preventive interventions is important. The first step in the Van Mechelen prevention model is to determine the extent o...

The literature on the relation between jump biomechanics and jumper's knee indicates that a jump with horizontal displacement poses a threat for developing jumper's knee. Subjects with jumper's knee have been shown to display a stiff landing pattern characterized by a small range of motion. However, up to now only cross-sectional studies have been...

Numerous athletes with patellar tendinopathy (PT) use a patellar strap or sports tape during sports. This study's aim was to investigate the short-term effect of these orthoses on patellar tendon pain. Participants performed the single-leg decline squat, vertical jump test, and triple-hop test under four different conditions (patellar strap, sports...

The primary aim of this study is to investigate the effect of the use of a patellar strap on knee joint proprioception in both healthy participants and in patients with patellar tendinopathy (PT). Secondary aims are to examine whether there is a difference in effectiveness of the use of a patellar strap between participants with low and high propri...

Tendinopathy, the most prevalent tendon disorder which is considered as the clinical diagnosis of pain and dysfunction, is common in sports and its prevalence is ever-increasing. Despite the lack of clarity about risk factors, various preventive interventions for tendinopathy have been investigated. The main objective of this study is to review cur...

Patellar tendinopathy (jumper's knee) has a high prevalence in jumping athletes. Excessive load on the patellar tendon through high volumes of training and competition is an important risk factor. Structural changes in the tendon are related to a higher risk of developing patellar tendinopathy. The critical tendon load that affects tendon structure...

When participating in sport and exercise activities, various – often agedependent – injuries to any part of the spine are possible. The neck is most commonly injured in sports that involve contact, which place the cervical spine at risk of injury, in some cases with catastrophic consequences. The thoracic spine is less likely to be injured because...

Sports and exercise medicine deals with the medical care of the exercising individual. Strong evidence shows that physical inactivity increases the risk of many adverse health conditions, including major noncommunicable diseases such as coronary heart disease, type 2 diabetes, and breast and colon cancers and shortens life expectancy. Therefore, ex...

Regular participation in sports and exercise activities is considered beneficial for health but unfortunately sometimes sports injuries occur. Based on the onset of symptoms and the mechanism, sports injuries can be classified as either acute injuries (due to a single traumatic event) or overuse injuries (due to repetitive microtraumata). In this c...

This comprehensive book describes in detail how nuclear medicine and radiology can meet the needs of the sports medicine physician by assisting in precise diagnosis, clarification of pathophysiology, imaging of treatment outcome and monitoring of rehabilitation. Individual sections focus on nuclear medicine and radiologic imaging of injuries to the...

Being overweight or obese is associated with an elevated risk of tendon pathology. However, for sportspeople the epidemiological data linking weight or adiposity on one hand, and risk of tendon pathology on the other, are less consistent. Indeed, the mechanistic links between diet, adiposity and tendon pathology remain largely unexamined. Recent st...

In this case report a dislocation of the hip received during a judo competition is described. This extremely uncommon condition requires special attention because a dislocated femoral head should be reduced within six hours to reduce the risk of avascular necrosis of the femoral head (AVNFH). Safe return to the pre-injury level of sports depends on...

Introduction Numerous athletes with patellar tendinopathy (PT) use a patellar strap or sports tape during sports aiming to reduce their pain. Despite that theories are suggested about the working mechanisms of these orthoses,2 there is to our knowledge no scientific evidence supporting the use of these orthoses in this common overuse injury. The ai...

Introduction Many athletes with patellar tendinopathy are still participating in sports but have symptoms during or after activities. It is hard to decrease pain in-season with current treatments; eccentric exercises in-season have resulted in worsening of symptoms [Fredberg, 2008; Visnes, 2007]. Other exercise programs (isometric and isotonic exer...

Introduction Patellar tendinopathy (PT) is a painful, sports related overuse injury of the patellar tendon3 with a high prevalence in sports that require a lot of jumping and landing, like volleyball and basketball.4 Since PT can be very persistent and treatments do not guarantee recovery1 it is important to identify risk factors for this injury th...

Introduction Patellar tendinopathy (jumper’s knee – pain in the tendon and dysfunction) has a high prevalence, especially in jumping athletes like volleyball players. Excess load on the patellar tendon through high volumes of training and competition is an important risk factor [Visnes, 2014]. Structural changes in the tendon are related with a hig...

Introduction Lower extremity tendinopathy is a common injury in athletes, but it can also develop in non-athletes [Rolf, 1997; De Jonge, 2012]. Because tendinopathy not only has negative effects on sports participation, but also on the ability to work and quality of life [Fearon, 2014; Van der Worp, 2011], preventive measures should be developed. T...

Patellar tendinopathy (PT) is a common overuse injury of the patellar tendon in jumping athletes. In a recent large cross-sectional study from 2008 several factors were identified that may be associated with the etiology of PT. However, because of the study design no conclusions could be drawn about causal relations. The primary aim of the current...