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Prevalence of Achilles tendinopathy increases with age, leading to a weaker tendon with predisposition to rupture. Previous studies, investigating Achilles tendon (AT) properties, are restricted to standardized isometric conditions. Knowledge regarding the influence of age and pa-thology on AT response under functional tasks remains limited. Therefore, the aim of the thesis was to investigate the influence of age and pathology on AT properties during a single-leg vertical jump.
Healthy children, asymptomatic adults and patients with Achilles tendinopathy participated. Ultrasonography was used to assess AT-length, AT-cross-sectional area and AT-elongation. The reliability of the methodology used was evaluated both Intra- and inter-rater at rest and at maximal isometric plantar-flexion contraction and was further implemented to investigate tendon properties during functional task. During the functional task a single-leg vertical jump on a force plate was performed while simultaneously AT elongation and vertical ground reaction forces were recorded. AT compliance [mm/N] (elongation/force) and AT strain [%] (elongation/length) were calculated. Differences between groups were evaluated with respect to age (children vs. adults) and pathology (asymptomatic adults vs. patients).
Good to excellent reliability with low levels of variability was achieved in the assessment of AT properties. During the jumps AT elongation was found to be statistical significant higher in children. However, no statistical significant difference was found for force among the groups. AT compliance and strain were found to be statistical significant higher only in children. No significant differences were found between asymptomatic adults and patients with tendinopathy.
The methodology used to assess AT properties is reliable, allowing its implementation into further investigations. Higher AT-compliance in children might be considered as a protective factor against load-related injuries. During functional task, when higher forces are acting on the AT, tendinopathy does not result in a weaker tendon.
Background:
Exercising at intensities where fat oxidation rates are high has been shown to induce metabolic benefits in recreational and health-oriented sportsmen. The exercise intensity (Fat peak ) eliciting peak fat oxidation rates is therefore of particular interest when aiming to prescribe exercise for the purpose of fat oxidation and related metabolic effects. Although running and walking are feasible and popular among the target population, no reliable protocols are available to assess Fat peak as well as its actual velocity (V PFO ) during treadmill ergometry. Our purpose was therefore, to assess the reliability and day-to-day variability of V PFO and Fat peak during treadmill ergometry running.
Methods:
Sixteen recreational athletes (f = 7, m = 9; 25 ± 3 y; 1.76 ± 0.09 m; 68.3 ± 13.7 kg; 23.1 ± 2.9 kg/m 2 ) performed 2 different running protocols on 3 different days with standardized nutrition the day before testing. At day 1, peak oxygen uptake (VO 2peak ) and the velocities at the aerobic threshold (V LT ) and respiratory exchange ratio (RER) of 1.00 (V RER ) were assessed. At days 2 and 3, subjects ran an identical submaximal incremental test (Fat-peak test) composed of a 10 min warm-up (70 % V LT ) followed by 5 stages of 6 min with equal increments (stage 1 = V LT , stage 5 = V RER ). Breath-by-breath gas exchange data was measured continuously and used to determine fat oxidation rates. A third order polynomial function was used to identify V PFO and subsequently Fat peak . The reproducibility and variability of variables was verified with an int raclass correlation coef ficient (ICC), Pearson ’ s correlation coefficient, coefficient of variation (CV) an d the mean differences (bias) ± 95 % limits of agreement (LoA).
Results:
ICC, Pearson ’ s correlation and CV for V PFO and Fat peak were 0.98, 0.97, 5.0 %; and 0.90, 0.81, 7.0 %, respectively. Bias ± 95 % LoA was − 0.3 ± 0.9 km/h for V PFO and − 2±8%ofVO 2peak for Fat peak.
Conclusion:
In summary, relative and absolute reliability indicators for V PFO and Fat peak were found to be excellent. The observed LoA may now serve as a basis for future training prescriptions, although fat oxidation rates at prolonged exercise bouts at this intensity still need to be investigated.
This study aimed to determine the relative and absolute reliability of ultrasound (US) measurements of the thickness and echogenicity of the plantar fascia (PF) at different measurement stations along its length using a standardized protocol. Twelve healthy subjects (24 feet) were enrolled. The PF was imaged in the longitudinal plane. Subjects were assessed twice to evaluate the intra-rater reliability. A quantitative evaluation of the thickness and echogenicity of the plantar fascia was performed using Image J, a digital image analysis and viewer software. A sonography evaluation of the thickness and echogenicity of the PF showed a high relative reliability with an Intra class correlation coefficient of 0.88 at all measurement stations. However, the measurement stations for both the PF thickness and echogenicity which showed the highest intraclass correlation coefficient (ICCs) did not have the highest absolute reliability. Compared to other measurement stations, measuring the PF thickness at 3 cm distal and the echogenicity at a region of interest 1 cm to 2 cm distal from its insertion at the medial calcaneal tubercle showed the highest absolute reliability with the least systematic bias and random error. Also, the reliability was higher using a mean of three measurements compared to one measurement. To reduce discrepancies in the interpretation of the thickness and echogenicity measurements of the PF, the absolute reliability of the different measurement stations should be considered in clinical practice and research rather than the relative reliability with the ICC.