What does normal tendon structure look like? New insights into tissue characterization in the Achilles tendon.

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 < 0.001). Furthermore, female tendons contained significantly more echo type II, in both insertion and midportion compared with male tendons (P = 0.004 and P = 0.003, respectively). The results of this study, with respect to the MDC (minimum detectable change), highlight differences in the UTC echopattern in the normal population (sex and regional location), which are important considerations for future studies.

Is Achilles tendon blood flow related to foot pronation?

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.

Effect of a Home-based Balance Training Protocol on Dynamic Postural Control in Subjects with Chronic Ankle Instability.

The aim of this study was to establish the presence of postural deficits in subjects with chronic ankle instability (CAI) and to assess the effect of an 8-week balance training program on dynamic postural control. A total of 43 subjects with CAI and 31 controls participated in this case-control study. Participants with CAI performed an 8-week home-based balance training, including 3 sessions a week. As main outcome measure, postural control was quantified after a vertical drop by means of the dynamic postural stability index (DPSI). Perceptual outcomes were documented using the FADI, FADI-Sport and VAS scales. At baseline, subjects with CAI displayed higher anterior/posterior and vertical postural instability, a poorer DPSI, and lower subjective stability scores compared to the control group. After balance training, all subjective stability scores improved significantly, although no changes were noted for the stability indices. In conclusion, subjects with CAI have an impaired postural control. As a treatment modality, balance training exhibits the capability of improving the subjective feeling of instability in subjects with CAI. However, there was no effect on dynamic postural control. Further research on the explanatory mechanisms of balance training is warranted, and other training modalities should be considered.

Effect of tape on dynamic postural stability in subjects with chronic ankle instability.

The objective of our study was to evaluate the effect of taping on the dynamic postural stability during a jump landing protocol in subjects with chronic ankle instability (CAI). For this purpose, 28 subjects with CAI performed a sagittal and frontal plane landing task in a non-taped and taped condition. As main outcome measure, the dynamic postural stability index (DPSI) was calculated. In addition, subjective feelings of instability and perceived difficulty level were assessed. Furthermore, mechanical effectiveness of the tape on the ankle joint was determined by registering 3D kinematics. 3 subjects were excluded based on discomfort during the landing protocol. Study results indicated that the tape reduced plantar flexion and inversion at the ankle at touchdown and range of motion in the landing phase. There was, however, no effect on the DPSI or on its directional subcomponents. Subjective feelings of stability with tape improved significantly, whereas perceived difficulty did not change. In conclusion, our taping procedure did not improve postural control during a sagittal and frontal plane landing task in subjects with CAI. Perceived instability did improve and is considered an important treatment outcome, which suggests that taping could be considered as a treatment modality by clinicians.

Impact of (long) COVID on athletes' performance: a prospective study in elite football players.

OBJECTIVES: To investigate possible persistent performance deficits after severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection in elite athletes. METHODS: A prospective cohort study in three Belgian professional male football teams was performed during the 2020 - 2021 season. Participants were submitted to strength, jump, and sprint tests and an aerobic performance test (the Yo-Yo Intermittent Recovery test (YYIR)). These tests were repeated at fixed time intervals throughout the season. Assessment of SARS-CoV-2 infection was performed by a polymerase chain reaction (PCR) test before each official game. RESULTS: Of the 84 included participants, 22 were infected with SARS-CoV-2 during follow-up. At the first testing after infection (52.0 ± 11.2 days after positive PCR testing) significantly higher percentages of maximal heart rate (%HRmax) were seen - within the isolated group of infected players- during (p = .006) and after the YYIR (2 min after, p = .013), compared to pre-infection data. This increase in %HRmax was resolved at the second YYIR testing after infection (127.6 ± 33.1 days after positive PCR testing). Additionally, when comparing the first test after infection in formerly infected to non-infected athletes, significantly higher %HRmax were found during (p < .001) and after the YYIR test (p < .001),No significant deficits were found for the jump, muscular strength or sprint tests.Aerobic performance seems compromised even weeks after infection. Simultaneously, anaerobic performance seemed to be spared. Because of the potential detrimental effects on the immune system, caution might be advised with high-intensity exposure until aerobic performance is restored.KEY MESSAGESElite football players' aerobic performance seems to be affected for weeks after they return to sports after a SARS-CoV-2 infection.Similarly, anaerobic performance tests showed no discernible changes between both before and after SARS-CoV-2 infections.Regular YYIR testing is recommended to monitor aerobic performance after SARS-CoV-2 infection.

A prospective study of gait related risk factors for exercise-related lower leg pain.

The purpose of this study was to determine prospectively gait related risk factors for exercise-related lower leg pain (ERLLP) in 400 physical education students. Static lower leg alignment was determined, and 3D gait kinematics combined with plantar pressure profiles were collected. After this evaluation, all sports injuries were registered by the same sports physician during the duration of the study. Forty six subjects developed ERLLP and 29 of them developed bilateral symptoms thus giving 75 symptomatic lower legs. Bilateral lower legs of 167 subjects who developed no injuries in the lower extremities served as controls. Cox regression analysis revealed that subjects who developed ERLLP had an altered running pattern before the injury compared to the controls and included (1) a significantly more central heel-strike, (2) a significantly increased pronation, accompanied with more pressure underneath the medial side of the foot, and (3) a significantly more lateral roll-off. These findings suggest that altered biomechanics play a role in the genesis of ERLLP and thus should be considered in prevention and rehabilitation.

Intrinsic risk factors for inversion ankle sprains in females--a prospective study.

Ankle sprains are extremely common. However, very little is known about the variables that predispose individuals to these injuries. The purpose of this study was to examine prospectively intrinsic risk factors for inversion sprains in a young physically active female population. One hundred and fifty-nine female physical education students were evaluated for several possible intrinsic risk factors for inversion sprains at the beginning of their academic study. The evaluated intrinsic risk factors included anthropometrical and physical characteristics, ankle joint position sense, isokinetic ankle muscle strength, lower leg alignment characteristics, postural control and muscle reaction time during a sudden inversion perturbation. All sports injuries were registered during 1-3 years and exposure to sport was recorded (mean: 15.33+/-4.33 h a week). Thirty-two (20%) of the 159 females sprained their ankle. The number of ankle sprains per 1000 h of sports exposure was 0.75. The Cox regression analysis revealed that females with less accurate passive joint inversion position sense [hazard ratio (HR): 1.08, 95% confidence interval (CI): 1.02-1.14 for absolute error at 15 degrees inversion], a higher extension range of motion at the first metatarsophalangeal joint (HR: 1.03, 95% CI: 1.00-1.06) and less coordination of postural control (HR: 0.96, 95% CI: 0.93-1.00 for endpoint excursion; HR: 0.94, 95% CI: 0.89-0.99 for maximal endpoint excursion) are at greater risk of an ankle sprain. The findings of this study suggest that effective prevention and conservative rehabilitation of ankle inversion sprains should include attention to these variables.