PurposeThis study aimed to assess the influence of knee joint cooling on the in vivo mechanical properties of the patellar tendon.MethodsTwenty young, healthy women volunteered for the study. B-mode ultrasonography was used to record patellar tendon elongation during isometric ramp contraction of the knee extensors (5–7 s, 90° knee angle) and calculate tendon stiffness. Skin temperature was measured by infrared thermometry. Data were acquired before and after 30 min of local icing of the knee joint and compared by paired samples t-tests.ResultsAfter cold exposure, skin temperature as measured over the patellar tendon dropped by 16.8 ± 2.0 °C. Tendon stiffness increased from 2189 ± 551 to 2705 ± 902 N mm−1 (+25 %, p = 0.007). Tendon strain decreased by 9 % (p = 0.004). A small, albeit significant reduction in maximum tendon force was observed (−3.3 %, p = 0.03).ConclusionsKnee cooling is associated with a significant increase in patellar tendon stiffness. The observed tendon stiffening may influence the operating range of sarcomeres, possibly limiting the maximal force generation capacity of knee extensor muscles. In addition, a stiffer tendon might benefit rate of force development, thus countering the loss in explosiveness typically described for cold muscles.

The goal of this study was to investigate the effect of differences in water vapor permeability (WVP) of outdoor jackets on moisture management, subjective perceptions and physiological parameters under conditions typically encountered in outdoor sports. Four outdoor jackets differing only in their WVP were compared in a repeated measures study. A total of 19 subjects (nine females) were tested in a climatic chamber at 10℃ and 40% relative humidity. The protocol consisted of 15 min of rest, 50 min of treadmill running at 60% of the individual maximal running velocity, and 15 min of passive recovery. We found that jackets featuring greater WVP helped to reduce relative humidity underneath the jacket, resulting in less sweat residue in the clothing system and drier skin during exercise and rest. Subjects were also able to perceive the differences in the microclimate and reported feeling more comfortable and drier in the more permeable jackets. However, WVP did not have a significant effect on oxygen consumption, heart rate, tympanic temperature, overall loss of subjects’ body mass or on perceived exertion. It can be concluded that outdoor jackets with higher WVP benefit moisture management during submaximal exercise in cool temperatures by reducing relative humidity in the clothing system mostly during rest periods. This effect leads to a drier skin which favors perceived comfort and might reduce the after-chill effect. However, WVP of outdoor jackets neither significantly affects physiological responses nor perceived exertion during submaximal exercise in a cool environment.

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