Pearson Stephen J, Burgess Katherine, Onambele Gladys N L
Centre for Rehabilitation and Human Performance Research, Directorate of Sport, University of Salford, Manchester, England, United Kingdom.
Clin Biomech (Bristol). 2007 Jul;22(6):712-7. doi: 10.1016/j.clinbiomech.2007.02.006. Epub 2007 Apr 6.
Owing to the viscoelastic nature of tendons it may be that the total excursion and hence strain experienced by the tendon under load may be affected by the duration of contraction. Here we examine the effect of contraction duration on the measured in vivo mechanical properties of the patellar tendon.
Nine healthy young men aged 21 (SEM 0.5 years) performed three short (3-4s) and three long (10-12s) maximal ramped isometric contractions on an isokinetic dynamometer, with real-time recordings of patellar excursions using B-mode ultrasonography synchronised with forces to determine tendon mechanical properties.
Maximal patellar excursion was approximately 42% (P<0.001, effect size (r)=0.9) lower for the short 3.6 (SEM 0.4mm) vs. the long 6.2 (SEM 0.4mm) contractions. Similarly, across the range of forces tested, strain was approximately 42% (P<0.001, r=0.9) lower for the short vs. the long contractions 4.5 (SEM 0.5) vs. 8.0 (SEM 0.9%), respectively. Tendon stiffness however, was approximately 77% greater (4648 SEM 434 vs. 2633 SEM 257 N mm(-1), P<0.001, r=0.9) for short vs. long contractions.
Contraction duration significantly affects tendon strain and associated measures of stiffness at all levels of force. The implications of this finding are twofold in that the results: (a) indicate that in order to compare tendon mechanical properties within or across studies, duration of contraction must be standardised and (b) have possible implications on training protocols and associated injury risks.
由于肌腱的粘弹性，肌腱在负荷下的总偏移以及由此产生的应变可能会受到收缩持续时间的影响。在此，我们研究收缩持续时间对髌腱体内测量力学性能的影响。
9名年龄为21岁（标准误0.5岁）的健康年轻男性在等速测力计上进行了3次短时间（3 - 4秒）和3次长时间（10 - 12秒）的最大斜坡等长收缩，使用B型超声实时记录髌腱偏移，并与力同步以确定肌腱力学性能。
短时间3.6（标准误0.4毫米）收缩与长时间6.2（标准误0.4毫米）收缩相比，最大髌腱偏移降低了约42%（P<0.001，效应大小(r)=0.9）。同样，在测试的力范围内，短时间收缩的应变分别为4.5（标准误0.5）%，长时间收缩的应变分别为8.0（标准误0.9）%，短时间收缩的应变比长时间收缩的应变降低了约42%（P<0.001，r=0.9）。然而，短时间收缩的肌腱刚度比长时间收缩的肌腱刚度大约高77%（4648标准误434与2633标准误257 N/mm，P<0.001，r=0.9）。
收缩持续时间在所有力水平下均显著影响肌腱应变及相关的刚度测量值。这一发现的影响有两方面：(a) 表明为了在研究内部或研究之间比较肌腱力学性能，必须标准化收缩持续时间；(b) 对训练方案和相关损伤风险可能有影响。
