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Mechanical overload is considered the main cause of Achilles tendinopathy. In addition to tensile loads, it is believed that the Achilles tendon may also be exposed to compressive loads. However, data on intratendinous pressures are lacking, and consequently, their role in the pathophysiology of tendinopathy is still under debate. Therefore, we aimed to evaluate the intratendinous pressure changes in the Achilles tendon during stretching and eccentric loading. Twelve pairs of human cadaveric legs were mounted in a testing rig, and a miniature pressure catheter was placed through ultrasound-guided insertion in four different regions of the Achilles tendon: the insertion (superficial and deep layers), mid-portion, and proximal portion. Intratendinous pressure was measured during three simulated loading conditions: a bent-knee calf stretch, a straight-knee calf stretch, and an eccentric heel-drop. It was found that the intratendinous pressure increased exponentially in both the insertion and mid-portion regions of the Achilles tendon during each loading condition (p < 0.001). The highest pressures were consistently found in the deep insertion region (p < 0.001) and during the eccentric heel-drop (p < 0.001). Pressures in the mid-portion were also significantly higher than in the proximal portion (p < 0.001). These observations offer novel insights and support a role for compression in the pathophysiology of Achilles tendinopathy by demonstrating high intratendinous pressures at regions where Achilles tendinopathy typically occurs. To what extent managing intratendinous pressure might be successful in patients with Achilles tendinopathy by, for example, avoiding excessive stretching, modifying exercise therapy, and offering heel lifts requires further investigation.

Objective: To provide consensus on how to plan, organize and implement exercise-based injury prevention program (IPP) in sports. Design: Delphi. Setting: LimeSurvey platform. Participants: Experienced sports physical therapists from the International Federation of Sports Physical Therapy member countries. Main outcome measures: Factors related to sports IPP planning, organization and implementation. Results: We included 305 participants from 32 countries. IPP planning should be based on an athlete's injury history, on pre-season screening results, and on injury rates (respectively, 98%, 92%, 89% agreement). In total 97% participants agreed that IPP organization should depend on the athlete's age, 93% on the competition level, and 93% on the availability of low-cost materials. It was agreed that IPP should mainly be implemented in warm-up sessions delivered by the head or strength/conditioning coach, with physical training sessions and individual physical therapy sessions (respectively, 94%, 92%, 90% agreement). Conclusion: Strong consensus was reached on (1) IPP based on the athlete's injury history, pre-season screening and evidence-based sports-specific injury rates; (2) IPP organization based on the athlete's age, competition level, and the availability of low-cost materials and (3) IPP implementation focussing on warm-up sessions implemented by the strength/conditioning coach, and/or individual prevention sessions by the physical therapist. (c) 2022 Elsevier Ltd. All rights reserved.

Unlike in neurological patient populations, the effects of Extended Reality within the context of sports medicine have rarely been studied. This systematic review was conducted to investigate the value of Extended Realty-assisted rehabilitation and injury prevention strategies on injury rehabilitation and prevention outcomes.PubMed and Web of Science databases were consulted. The search strategy consisted of the terms Virtual Reality (Intervention), rehabilitation and injury prevention (Outcome) and healthy athletes or athletes with a musculoskeletal sports injury (Population). After eligibility and Risk of Bias screening, ten articles were included. Risk of Bias analysis resulted in a level of evidence varying between C (three articles), B (six articles) and A2 (one article) scores.Extended Reality was found to provide an added value for both sports injury prevention and rehabilitation outcomes. It particularly provides clinicians with the opportunity to address the underlying biomechanical risk profile for common sports injuries, allowing the athletes to train protective movement patterns more effectively.More large-scale high-quality prospective research is needed in order to determine whether Extended Reality-assisted therapy is superior to conventional therapy in sports rehabilitation and injury prevention circles with strong conclusive evidence.

ObjectivesThe aim of this study was to investigate the association between SARS-CoV-2 infection and muscle strain injury in elite athletes.MethodsA prospective cohort study in three Belgian professional male football teams was performed during the first half of the 2020–2021 season (June 2020–January 2021). Injury data were collected using established surveillance methods. Assessment of SARS-CoV-2 infection was performed by a PCR test before each official game.ResultsOf the 84 included participants, 22 were infected with SARS-CoV-2 and 14 players developed a muscle strain during the follow-up period. Cox’s proportional hazards regression analyses demonstrated a significant association between SARS-CoV-2 infection and the development of muscle strain (HR 5.1; 95% CI 1.1 to 23.1; p=0.037), indicating an increased risk of developing muscle strains following SARS-CoV-2 infection. All athletes who sustained a muscle strain after infection were injured within the first month (15.71±11.74 days) after sports resumption and completed a longer time in quarantine (14.57±6.50 days) compared with the infected players who did not develop a muscle strain (11.18±5.25 days).ConclusionThis study reported a five times higher risk of developing a muscle strain after a SARS-CoV-2 infection in elite male football players. Although this association should be examined further, it is possible that short-term detraining effects due to quarantine, and potentially pathological effects of the SARS-CoV-2 infection are associated with a higher risk of muscle strain injury.

ObjectiveTo examine the effects of autoregulated (AUTO) and non-autoregulated (NAUTO) blood flow restriction (BFR) application on adverse effects, performance, cardiovascular and perceptual responses during resistance exercise.MethodsFifty-six healthy participants underwent AUTO and NAUTO BFR resistance exercise in a randomised crossover design using a training session with fixed amount of repetitions and a training session until volitional failure. Cardiovascular parameters, rate of perceived effort (RPE), rate of perceived discomfort (RPD) and number of repetitions were investigated after training, while the presence of delayed onset muscle soreness (DOMS) was verified 24 hours post-session. Adverse events during or following training were also monitored.ResultsAUTO outperformed NAUTO in the failure protocol (pConclusionAutoregulation appears to enhance safety and performance in both fixed and failure BFR-training protocols. AUTO BFR training did not seem to affect cardiovascular stress differently, but was associated with lower DOMS, perceived effort and discomfort compared with NAUTO.Trial registration numberNCT04996680.

Mechanical overload is considered the main cause of Achilles tendinopathy. In addition to tensile loads, it is believed that the Achilles tendon may also be exposed to compressive loads. However, data on intratendinous pressures are lacking, and consequently, their role in the pathophysiology of tendinopathy is still under debate. Therefore, we aimed to evaluate the intratendinous pressure changes in the Achilles tendon during stretching and eccentric loading. Twelve pairs of human cadaveric legs were mounted in a testing rig, and a miniature pressure catheter was placed through ultrasound-guided insertion in four different regions of the Achilles tendon: the insertion (superficial and deep layers), mid-portion, and proximal portion. Intratendinous pressure was measured during three simulated loading conditions: a bent-knee calf stretch, a straight-knee calf stretch, and an eccentric heel-drop. It was found that the intratendinous pressure increased exponentially in both the insertion and mid-portion regions of the Achilles tendon during each loading condition (p 0.001). The highest pressures were consistently found in the deep insertion region (p 0.001) and during the eccentric heel-drop (p 0.001). Pressures in the mid-portion were also significantly higher than in the proximal portion (p 0.001). These observations offer novel insights and support a role for compression in the pathophysiology of Achilles tendinopathy by demonstrating high intratendinous pressures at regions where Achilles tendinopathy typically occurs. To what extent managing intratendinous pressure might be successful in patients with Achilles tendinopathy by, for example, avoiding excessive stretching, modifying exercise therapy, and offering heel lifts requires further investigation.

Although isokinetic strength testing is commonly used in hamstring strain injury (HSI) rehabilitation and prevention, research findings concerning its predictive value remain inconclusive. Existing research focuses on peak torque (PT) and angle of PT, not analysing the torque behaviour throughout the testing range of motion (ROM). This study intended to assess the value of isokinetic curve evaluation in association with HSI. A sample of 116 male football players with and without a recent HSI history was submitted to bilateral isokinetic assessment of the knee and hip muscles. Raw isokinetic data were filtered and normalized prior to curve analysis submission in MATLAB. Torque development of each muscle group throughout the entire testing ROM was assessed using HSI history as an independent variable. Curve analysis revealed significant differences in torque behaviour in function of injury history. Players with an HSI history demonstrated significantly stronger concentric knee flexion and extension, eccentric knee extension and concentric hip extension patterns compared to the controls and their uninjured limb. HSI history was also associated with lower concentric hip flexion torques and lower mixed H:Q ratios compared to the control group and their contralateral limb. HSI history was associated with altered knee and hip muscle strength profiles, potentially due to isolated focus on local strength training in rehabilitation or mechanisms of neuromuscular inhibition. Because the differences in torque amplitude were range-dependent and did not systematically concur with the point of PT achievement, isokinetic strength evaluation should most probably be conducted using curve analysis.

Background : Hamstring strain injuries (HSI) are prevalent in team sports and occur frequently in the latter phase of matches. In the search for interindividual factors that determine muscle fatigue and possibly injury risk, muscle fibre typology is a likely candidate. It was the aim of the study to determine whether muscle fibre typology is a risk factor for HSI. Methods : A prospective cohort study was conducted over 3 seasons in professional football players competing in the Belgian Jupiler Pro League (n=118) and in the English Premier League (n=47), and a total of 27 hamstring strain injuries were sustained during this period. The muscle fibre typology was non-invasively estimated using proton magnetic resonance spectroscopy, and was characterized as a fast, slow, or intermediate typology based on the carnosine concentration in the soleus. A multivariate cox model was used to identify risk factors for HSI. Results : Football players exhibit a wide variety of muscle typologies (slow typology=44.9%; intermediate typology=39.8%, fast typology=15.3%). In the combined cohort, players with a fast typology displayed a 5.3-fold (95% CI 1.92-14.8, P=0.001) higher risk than slow typology players to sustain an index HSI. This was also independently observed in both leagues separately as respectively a 6.7-fold (95% CI 1.3-34.1; P=0.023) and a 5.1-fold (95% CI 1.2-20.4; P=0.023) higher chance was found in fast typology players than slow typology players of the Jupiler Pro League and the Premier League cohort. Conclusion : We discovered muscle fibre typology as a novel and potent risk factor for HSI in team sports.

Context: Although training with an aquabag (AB) has gained popularity, there is a lack of evidence of its effect. This study wanted to evaluate the effect of AB implementation on muscle activity of core and lower limb muscles during 3 functional exercises. Design: Cross-sectional observational study. Methods: Twenty healthy subjects performed a squat, lunge, and step-up, while using a stick and an AB. Surface electromyography signals were recorded from the trunk, pelvis, and thigh muscles in the dominant leg. Linear-mixed models were used to analyze the normalized surface electromyography signals. Results: Results demonstrated a significant increase in muscle activity of the back muscles during all 3 exercises (P P = .003), abdominals during squat (P = .034) and step-up (P = .046), hamstrings during lunge (P = .008) and step-up (P = .008), and gluteal muscles during lunge (P P = .010, respectively). Conclusions: These results indicate that an AB promotes functional strength training by demanding compensatory/additional activity of both stabilizing muscles (specifically in the core and pelvis regions) and prime movers of the lower limb. The authors recommend the use of an AB to enhance training and rehabilitation effects.

Return to play (RTP) criteria after hamstring strain injuries (HSIs) help clinicians in deciding whether an athlete is ready to safely resume previous sport activities. Today, functional and sport-specific training tests are the gold standard in the decision-making process. These criteria lead to an average RTP time between 11 and 25 days after a grade 1 or 2 HSI. However, the high re-injury rates indicate a possible inadequacy of the current RTP criteria. A possible explanation for this could be the neglect of biological healing time. The present review shows that studies indicating time as a possible factor within the RTP-decision are very scarce. However, studies on biological muscle healing showed immature scar tissue and incomplete muscle healing at the average moment of RTP. Twenty-five percent of the re-injuries occur in the first week after RTP and at the exact same location as the index injury. This review supports the statement that functional recovery precedes the biological healing of the muscle. Based on basic science studies on biological muscle healing, we recommend a minimum period of 4 weeks before RTP after a grade 1 or 2 HSI. In conclusion, we advise a comprehensive RTP functional test battery with respect for the natural healing process. Before deciding RTP readiness, clinicians should reflect whether or not it is biologically possible for the injured tissue to have regained enough strength to withstand the sport-specific forces. In an attempt to reduce the detrimental injury-reinjury cycle, it is time to start considering (biological healing) time.

Objective To identify the role of sports physical therapists (PT) in the injury prevention process and to compare the structure of preventive programs and associated (organization) policies applied in athletic organizations and sports teams of varying gender and level world-wide. Design: cross-sectional study. Setting LimeSurvey platform. Participants Sports PT working with athletes invited through the International Federation of Sports Physical Therapy. Main outcome measures Sports injury prevention program (IPP) structure and implementation. Results 414 participants fully participate in this survey study. Athlete's injury history (68.84%), the most common injuries within the sport modality (67.87%) and athlete's preseason screening results (64.01%) were most frequently used to customize IPPs. Warm-up (70.04%) and individually PT-guided exercise-therapy (70.04%) were the preferred methods to organize the prevention routine. The main barrier for IPP implementation was lack of time within the athlete's weekly training schedule (66.66%). The majority of the participants (72.84%) reported to evaluate the perception of IPP's effect by comparing current and preceding seasons' injury occurrences. Conclusion These survey results are the first identifying contemporary sports injury prevention organization and implementation policies on an international level. This information might support the sports PT community in improving and standardizing IPP (implementation) strategies worldwide.

Objective To identify the role of sports physical therapists (PT) in the organization of injury registration and preseason assessment, applied in athletic organizations and sports teams of different gender and level world-wide. Design cross-sectional study. Setting LimeSurvey platform. Participants Sports PTs working with athletes invited through International Federation of Sports Physical Therapy. Main outcome measures injury registration and athlete's screening. Results 414 sports PTs participated in this international survey (mean age of 37.66 (SD = 9.38) years). 340 participants indicated that the PT as the responsible for injury registration. Barriers to properly register injury throughout the season were indicated by 157 sports PT and 86 (54.77%) indicated a lack of time on their routine as the main factor. 93 participants (30.09%) indicated that they customize the prevention program based on the preseason assessment. Sports PTs who reported not performing a preseason assessment (92 participants - 22.22%) mainly indicated this to be consequence of lack of structure in the organization (44 participants – 47.82%). Conclusion The majority of the sports PTs participate on injury registration and perform preseason assessment in athletes. However, lack of time in their routine and structure in the organization were recognized as the most important barriers to organize these properly.

The number one goal of the sports physical therapist is to make sure that the athlete is in optimal shape to perform, but with a minimal risk for developing an injury at the same time. The aim of this International Federation of Sports Physical Therapy (IFSPT) Perspective is to raise awareness about the importance of contextual and behavioral factors when planning and implementing injury prevention. Also, it outlines the potential role of the IFSPT as a facilitator of data and information exchange among sports physical therapists worldwide., This International Perspective aims to describe the role of IFSPT in prevention of injuries throughout the world.

Background: Previous research of a young adult population identified a lower increase in Achilles tendon blood flow immediately after a running activity as a significant predictor for the development of Achilles tendinopathy (AT). Furthermore, advancing age is often mentioned as a risk factor for the development of AT, and the highest incidence for AT is reported to occur in middle-aged recreational male athletes. Purpose: To investigate the effect of age, sex, and type of physical activity on the increase in Achilles tendon blood flow. Study Design: Controlled laboratory study. Methods: Blood flow measurements of 33 subjects aged 18 to 25 years and 30 subjects aged 40 to 55 years were obtained before and after 4 physical activities performed in randomized order: running, cycling, dynamic stretching, and rope skipping. Blood flow measurements of the Achilles tendon were performed before, immediately after, 5 minutes after, and 10 minutes after the physical activities. The effect of age, sex, and physical activities on the increase in blood flow was investigated with linear mixed models. Results: The results of this study identified that running, rope skipping, and cycling resulted in a significant increase in tendon blood flow ( P ≤ .001), whereas stretching did not. Prominent was the finding that the increase in blood flow after activity was significantly lower in the older population as compared with the younger population ( P < .001). Furthermore, male participants in the older group showed a significantly lower increase in tendon blood flow than did their female counterparts ( P = .019). Conclusion: This study identified that sex and age significantly influence the increase in blood flow after activity, possibly explaining the increased risk for AT among middle-aged recreational athletes. Clinical Relevance: This study possibly identified one of the mechanisms explaining why an older male population is at increased risk for developing AT. Given that the lower increase in blood flow is an identified risk factor according to previous research, preventative measures should focus on improving this blood flow during physical activity in the physically active older male population. Registration: NCT03218605 ( ClinicalTrials.gov identifier).

Background: Several risk factors have been suggested in the development of Achilles tendinopathy, but large-scale prospective studies are limited. Purpose: To investigate the role of the vascular response to activity of the Achilles tendon, tendon thickness, ultrasound tissue characterization (UTC) of tendon structure, and foot posture as possible risk factors in the development of Achilles tendinopathy. Study Design: Cohort study; Level of evidence, 2. Methods: The study began with 351 first-year students at Ghent University. After 51 students were excluded, 300 were tested in the academic years 2013-2014 and 2014-2015 and were followed prospectively for 2 consecutive years by use of a multilevel registration method. Of those, 250 students were included in the statistical analysis. At baseline, foot posture index and UTC were investigated bilaterally. Blood flow and tendon thickness were measured before and after a running activity. Cox regression analyses were performed to identify significant contributors to the development of Achilles tendinopathy. Results: During the 2-year follow-up, 27 of the included 250 participants developed Achilles tendinopathy (11%). Significant predictive effects were found for female sex and blood flow response after running ( P = .022 and P = .019, respectively). The risk of developing Achilles tendinopathy increased if the blood flow increase after running was reduced, regardless of sex, foot pronation, and timing of flow measurements. The model had a predictive accuracy of 81.5% regarding the development of Achilles tendinopathy, with a specificity of 85.0% and a sensitivity of 50.0%. Conclusion: This prospective study identified both female sex and the diminished blood flow response after running as significant risk factors for the development of Achilles tendinopathy. UTC of tendon structure, Achilles tendon thickness, and foot posture did not significantly contribute to the prediction of Achilles tendinopathy. A general evaluation of tendon structure by UTC, measurement of tendon thickness, or determination of the foot posture index will not allow clinicians to identify patients at risk for developing Achilles tendinopathy. Furthermore, it may be possible to improve blood flow after activity by using noninvasive techniques (such as prostaglandins, compression stockings, heat, massage, and vibration techniques). These techniques may be useful in the prevention and management of Achilles tendinopathy, but further research is needed.

Recently, ultrasound tissue characterization (UTC) was introduced as a reliable method for quantification of tendon structure. Despite increasing publications on the use of UTC, it is striking that there is a lack of normative data in active adolescents. Therefore, the aim of this study was to provide normative values of the Achilles tendon as quantified by UTC. Seventy physiotherapy students (26 male and 44 female students) with no history of Achilles tendon injuries were recruited. The Achilles tendons were scanned with UTC to characterize tendon structure. This study demonstrated that Achilles tendons of active, healthy adolescents contained 54.6% echo type I, 42.8% echo type II, 2.2% echo type III, and 0.3% echo type IV at midportion. The comparison between insertion and midportion of the tendon showed more echo type II at insertion (P

In the etiology of Achilles tendinopathy (AT), it is frequently suggested that excessive pronation causes a vascular constriction of the Achilles tendon, described as the "whipping phenomenon" (Clement et al., 1984). Although previous studies focused on the association between pronation and AT, it is striking that the underlying association between foot pronation and blood flow has not been studied yet. Therefore, the aim of this study was to investigate whether the amount of pronation during running influences the Achilles tendon blood flow. Twenty-five experienced runners, aged 34.5±10.2 years, participated in this study. 2D-lower limb kinematics during barefoot and shod running in both frontal and sagittal plane were assessed. Blood flow of the Achilles tendon was measured before and after barefoot and shod running, using the oxygen-to-see device. The results of this study showed a significant effect of eversion excursion on the increase in Achilles tendon blood flow after shod running. More specifically, the more the eversion excursion observed, the lower the increase in blood flow (P=.013). We therefore suggest, in individuals with increased inversion at touchdown and increased eversion around midstance during shod running, that antipronation measures could be useful in both preventing and managing Achilles tendinopathy.

Background The most popular hypothesis of the etiology of Achilles tendinopathy suggests that excessive pronation causes conflicting rotational motions, leading to a vascular constriction of the Achilles tendon, described as the “whipping phenomenon” (Clement et al., 1984). Although several studies identified pronation as a risk factor for the development of Achilles tendinopathy, the hypothesis that foot pronation causes vascular constriction of the tendon has not been investigated. Objective Therefore, the aim of this study was to investigate whether the amount of pronation during running influences the Achilles tendon blood flow. Design Cross-sectional study. Setting Runners Service Lab, Zwijndrecht, Belgium. Patients (or Participants) Twenty-five experienced runners (average running time 6.1±2.4 hours/week) aged 34.5±10.2 years participated in this study. Interventions (or Assessment of Risk Factors) 2D-lower limb kinematics during barefoot and shod running in both frontal and sagittal plane were assessed. Blood flow of the Achilles tendon was measured before and after barefoot and shod running, by use of the oxygen-to-see device. Main Outcome Measurements The increase of blood flow after running was registered as outcome variable. Mixed models analyses were executed with kinematic variables as fixed predictors. Results The results of this study confirm that the more pronation excursion during running, the lower the increase in blood flow after running in both insertion and midportion (p=0.085 and 0.037, respectively). In addition, this study revealed that a higher average pronation velocity indicates a lower increase in blood flow after running at insertion (p=0.044). Next, this study also showed that the dorsiflexion excursion or the foot strike pattern was not correlated with blood flow after running. Conclusions We can conclude that our findings indicate that foot pronation causes vascular constriction of the Achilles tendon, and therefore support this aspect of the whipping phenomenon.

Introduction It is still not clear what the relationship is between the vascular response of an Achilles tendon and the development of an overuse injury. Methods This systematic review is reported following the PRISMA guideline. An electronic database search was conducted on PubMed and Web Of Science by using multiple keyword combinations regarding the PICO-question: The influence of neovascularization and blood flow (I) on the development of Achilles tendon injury (O) in the AT (P). Results Sixteen articles were included in this review. For the 3 case-control studies the mean score was 3.6 on 6 [Alfredson, 2003; Malliaras, 2006; Ohberg, 2001]. Seven cross-sectional studies were scored on a total of 4 items [Boesen, 2006; Boesen 2012, Fahlstrom 2010; Malliaras P, 2008; Malliaras 2012; Reiter 2004; van Snellenberg 2007]. The mean score here is 2.4 on 4. Six cohort designed studies gained a mean of 6.16 on 8 [Boesen 2006; Hirschmuller 2012, Jhingan 2011, Knobloch 2006, Mahieu 2010, Ram 2013]. The cohort designed studies have the strongest mean methodological score. Only one study fails in the methodological scoring [van Snellenberg 2007]. Thirteen out of sixteen studies have a level of evidence B. Only one study has a level of evidence A2 [Hirschmuller 2012]. Two studies have a level of evidence C [Boesen 2012, Malliaras 2012]. Discussion The prognostic value of increased blood flow or neovascularisation inside the tendon is not clear. Furthermore it can be seen in symptomatic and in asymptomatic subjects, for example after physical activity. Five studies look at the neovessels after one single exercise moment, three other studies use an exercise protocol of a longer duration. Different loadings, different Doppler settings result in conflicting evidence. Most of the authors believe that neovascularisation could be a physiological adaptation, even in asymptomatic persons. In the different studies, neovascularisation does not always correlate with pain. Otherwise neovascularisation is sometimes related with structural changes. Some studies assume that the development of an overuse injury is related to structural changes inside the tendon and to pain. In conclusion,there is no conclusive answer found on the question “Does neovascularization and blood flow play a role in the development of Achilles tendon injuries?”. Further prospective research is needed to give a conclusive answer. References Alfredson H., et al .. Knee Surg Sports Traumatol Arthrosc. 2003 Sep;11(5):334–8 Boesen M. I., et al . Am J Sports Med . 2006 Dec;34(12):2013–21 Boesen M. I., et al . Scand J Med Sci Sports . 2006 Dec;16(6):463–9 Boesen A. P., et al . Am J Sports Med. 2012;40(3):548–55 Fahlstrom M. and Alfredson H. Br J Sports Med. 2010;44(2):140–3 Hirschmuller A., et al . Med Sci Sports Exerc. 2012;44(2):199–205 Jhingan S., et al . Muscles Ligaments Tendons J. 2011;1(2):51–6 Knobloch, K., et al . Am J Sports Med. 2006;34(1):92–7 Mahieu N, et al . Int J Sports Med. 2010;31(12):901–5 Malliaras P, et al . Am J Sports Med. 2008;36(11):2210–5 Malliaras P, et al . Int J Sports Med. 2012;33(6):480–4 Malliaras P, et al . Scand J Med Sci Sports. 2012;22(2):149–55 Ohberg L, et al . Knee Surg Sports Traumatol Arthrosc. 2001;9(4):233–8 Ram R, et al . Clin Invest Med. 2013;36(4):E197–206 Reiter M, et al . Int J Sports Med. 2004;25(4):301–5 van Snellenberg W, et al . Scand J Med Sci Sports. 2007;17(5):530–4

Introduction An inadequate blood supply plays an important role in the development of injuries. It is known that physical activity has an influence on the blood flow of a tendon. However, it remains unclear which type of activity leads to the highest increase in blood flow. Therefore, the aim was to compare the immediate effect of 5 different physical activities (running, stretching, plyometrics, eccentric heel drops, T-test) on the blood flow of the Achilles tendon. Methods Thirty healthy subjects performed each of the 5 activities spread over a period of 3 weeks. Blood flow, saturation and haemoglobin were measured biateral before and after each activity. 12 well-defined tendon points were summarised into 4 regions: insertion, distal midportion, proximal midportion and musculotendinous junction. Changes were statistically analysed using a mixed model analysis. Results At the insertion, running is the only activity which has an immediate effect on the Achilles blood flow (p When compared to the other 4 physical activities, running differs significantly, especially at the insertional region and at the distal midportion. The P-values range from 0.000 to 0.016. In the proximal midportion, running also shows the highest increase and differs significantly from heel drops, stretching and T-test. At the musculotendon unit, only 2 significant P-values are seen; between running and stretching and between running and heel drops. The results of saturation mainly follow those of blood flow whereas the results of haemoglobin are unclear. Discussion The results demonstrate that running implicates the highest increase in blood flow of the Achilles tendon and this throughout the four regions of the Achilles tendon. The present results are in agreement with the observation of a decrease in blood flow after eccentric training and stretching (Knobloch et al., 2007). It is reasonable to assume that due to a tendon stretch the blood vessels within the tendon stretch and become thinner, which results in a slower flow. The higher increase due to running might be explained by the exercising time. The duration of tuck jumps and T-test may not have been sufficient to induce a vasodilation to increase tendon blood flow (Malliaras et al., 2012). In conclusion, if one wants to increase the blood flow of a tendon, it can be recommended to perform physical activities, in which the tendon is loaded cyclically. References Alfredson H, et al. Knee Surg Sports Traumatol Arthrosc, 2006;14:399–401 Boesen MI, et al. Am J Sports Med. 2006;34(12):2013–2021 Boesen MI, et al. Scand J Med Sci Sports. 2006;16(6):463–469 Boesen AP, et al. Am J Sports Med. 2012;40(3):548–555 Fahlstrom M, et al. Br J Sports Med. 2010;44:140–143 Hirschmuller A, et al, Med Sci Sports Exerc. 2012;44(2):199–205 Kjaer M, et al., Scand J Med Sci Sports. 2000;10(6):326–331 Knobloch K, et al. Am J Sports Med. 2006;34(1):92–97 Knobloch K, et al. J Orthop Sports Phys Ther. 2007;37(5):269–276 Kubo K, et al. Acta Physiol (Oxf). 2008;193(3):257–264 Langberg H, et al. Eur J Appl Physiol. 2001;84(3):246–248 Mahieu N, et al. Int J Sports Med. 2010;31(12):901–5 Malliaras P, et al, Am J Sports med. 2008;36(11):2210–2215 Malliaras P, et al. Int J Sports med. 2012;33:480–484 Ohberg L, et al. Knee Surg Sports Traumatol Arthrosc. 2004;12(5):465–470 Reiter M, et al. Int J Sports Med. 2004;25(4):301–305 Van Snellenberg W, et al. Scand J Med Sci Sports. 2007;17(5):530–534