Centre for Sports and Exercise Medicine, Queen Mary, University of London, UK.
J Biomech. 2013 Jul 26;46(11):1893-9. doi: 10.1016/j.jbiomech.2013.04.022. Epub 2013 Jun 14.
Loading leads to tendon adaptation but the influence of load-intensity and contraction type is unclear. Clinicians need to be aware of the type and intensity of loading required for tendon adaptation when prescribing exercise. The aim of this study was to investigate the influence of contraction type and load-intensity on patellar tendon mechanical properties.
Load intensity was determined using the 1 repetition maximum (RM) on a resistance exercise device at baseline and fortnightly intervals in four randomly allocated groups of healthy, young males: (1) control (no training); (2) concentric (80% of concentric-eccentric 1RM, 4×7-8); (3) standard load eccentric only (80% of concentric-eccentric 1RM, 4×12-15 repetitions) and (4) high load eccentric (80% of eccentric 1RM, 4×7-8 repetitions). Participants exercised three times a week for 12 weeks on a leg extension machine. Knee extension maximum torque, patellar tendon CSA and length were measured with dynamometry and ultrasound imaging. Patellar tendon force, stress and strain were calculated at 25%, 50%, 75% and 100% of maximum torque during isometric knee extension contractions, and stiffness and modulus at torque intervals of 50-75% and 75-100%. Within group and between group differences in CSA, force, elongation, stress, strain, stiffness and modulus were investigated. The same day reliability of patellar tendon measures was established with a subset of eight participants.
Patellar tendon modulus increased in all exercise groups compared with the control group (p<0.05) at 50-75% of maximal voluntary isometric contraction (MVIC), but only in the high eccentric group compared with the control group at 75-100% of MVIC (p<0.05). The only other group difference in tendon properties was a significantly greater increase in maximum force in the high eccentric compared with the control group (p<0.05). Five repetition maximum increased in all groups but the increase was significantly greater in the high load eccentric compared with the other exercise groups (p<0.05).
Load at different intensity levels and contraction types increased patellar tendon modulus whereas muscle strength seems to respond more to load-intensity. High load eccentric was, however, the only group to have significantly greater increase in force, stiffness and modulus (at the highest torque levels) compared with the control group. The effects and clinical applicability of high load interventions needs to be investigated further.
负载会导致肌腱适应，但负载强度和收缩类型的影响尚不清楚。临床医生在开运动处方时需要了解肌腱适应所需的负载类型和强度。本研究旨在探讨收缩类型和负载强度对髌腱机械性能的影响。
在基线和两周间隔时，使用阻力运动器械上的 1 次重复最大（1RM）确定负载强度，在 4 个随机分配的健康年轻男性组中：（1）对照组（无训练）；（2）向心组（80%的向心-离心 1RM，4×7-8 次）；（3）标准负荷离心组（80%的向心-离心 1RM，4×12-15 次）和（4）高负荷离心组（80%的离心 1RM，4×7-8 次）。参与者每周在腿部伸展机上进行 3 次锻炼，持续 12 周。使用测力计和超声成像测量膝关节伸展时的最大扭矩、髌腱 CSA 和长度。在等长膝关节伸展收缩过程中，在 25%、50%、75%和 100%最大扭矩时计算髌腱力、应力和应变，在扭矩间隔 50-75%和 75-100%时计算刚度和模量。研究了 CSA、力、伸长、应力、应变、刚度和模量的组内和组间差异。用 8 名参与者的子集确定了髌腱测量的同日可靠性。
与对照组相比，所有运动组的髌腱模量在 50-75%的最大自主等长收缩（MVIC）时均增加（p<0.05），但仅在高离心组与对照组在 75-100%MVIC 时增加（p<0.05）。腱特性的唯一其他组间差异是高离心组的最大力增加明显大于对照组（p<0.05）。所有组的 5 次重复最大都增加，但高负荷离心组的增加明显大于其他运动组（p<0.05）。
不同强度水平和收缩类型的负载增加了髌腱的模量，而肌肉力量似乎对负载强度的反应更大。然而，与对照组相比，高负荷离心组的力、刚度和模量（在最高扭矩水平）增加明显更大。需要进一步研究高负荷干预的效果和临床适用性。
