Training & Testing
Life Science (Sports Sciences), University of Tokyo, Tokyo, Japan
Key words ▶ blood volume ● ▶ oxygen saturation ● ▶ tendon ● ▶ human ●
Previous studies demonstrated that treatment involving eccentric training was effective in the conservative management of chronic tendinosis. However, the mechanisms for these phenomena are unknown. The purpose of this study was to compare changes in blood circulation of the tendons after the repeated concentric and eccentric contractions. 11 healthy males volunteered for this study. Subjects performed the repeated concentric (CON) and eccentric (ECC) contractions (5 sets of 10 maximal voluntary contractions) of the
accepted after revision November 14, 2014 Bibliography DOI http://dx.doi.org/ 10.1055/s-0034-1398649 Published online: March 3, 2015 Int J Sports Med 2015; 36: 481–484 © Georg Thieme Verlag KG Stuttgart · New York ISSN 0172-4622 Correspondence Dr. Keitaro Kubo Life Science (Sports Sciences) University of Tokyo Komaba 3-8-1 Meguro Tokyo Japan 153-8902 Tel.: + 81/3/5454 6860 Fax: + 81/3/5454 4317 [email protected]
Tendon injuries from overuse are a major problem among recreational and competitive athletes. Previous studies have shown that treatment involving eccentric training has been effective in the conservative management of chronic tendinosis [1, 10, 19, 21]. Furthermore, nonsurgical treatment with eccentric training reduced the need for surgical treatment for patients with chronic tendinosis. For example, Mafi et al.  reported that after the eccentric training regimen 82 % of the patients were satisfied and had resumed their previous activity level, compared to 36 % of the patients who were treated with the concentric training regimen. However, the mechanisms for the efficacy of eccentric training involved in physiologic tendon response to eccentric loading are unknown. It is known that tendon injuries and disorders have been associated with disturbances in tendon vasculature . These changes within the tendons may result in the decline of blood circulation and collagen synthesis. Therefore, the injured tendons require ample supply of blood for their restoration and treatment [2, 8]. On the other hand, previous studies demonstrated that the muscle activation level and energy cost were
plantar flexors. During and after repeated contractions, oxyhemoglobin (Oxy), deoxyhemoglobin (Deoxy), total hemoglobin (THb), and oxygen saturation (StO2) of the Achilles tendons were measured using red laser lights. Oxy and THb increased during and after ECC, but not CON. Deoxy decreased during both CON and ECC. Increase in StO2 during and after ECC was greater than that during and after CON. These results suggested that changes in blood circulation of the Achilles tendon during and after repeated eccentric contractions were more remarkable than those during and after repeated concentric contractions.
lower for eccentric contractions than concentric contractions, although the exerted force level during eccentric contractions was higher than that during concentric contractions [3, 22]. At present, however, we cannot say for certain whether these characteristics of eccentric contractions affect blood circulation of tendons. Recently, we measured blood circulation (blood volume and oxygen saturation) in human tendons using 3 red laser lights [12–15]. With this technique, we found that changes in blood circulation of tendons were different among the different contraction modes. We reported that blood volume of the patellar tendon did not change after 3 months of isometric knee extension training, although it increased significantly after dynamic training . Considering these findings, changes in blood circulation of the tendons after eccentric training would be remarkable compared to other contraction mode regimens. In the present study, we aimed to compare changes in blood circulation of the tendons after the repeated concentric and eccentric contractions. We hypothesized that increases in blood volume and oxygen saturation of the tendon would be greater after eccentric than after concentric contractions.
Kubo K. Effect of repeated contractions on tendon blood circulation … Int J Sports Med 2015; 36: 481–484
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Effects of Repeated Concentric and Eccentric Contractions on Tendon Blood Circulation
482 Training & Testing Materials and Methods
Each subject performed 2 tests on 2 separate days, with at least 2 but no more than 4 weeks between sessions. The order of the 2 experimental conditions was randomized for each subject. Subjects sat on a chair to acclimate themselves to the laboratory conditions for 20 min prior to the experiment. Initially, subjects lay in a comfortable prone position on a test bench for a 15 min rest period (baseline). The subject lay prone on a test bench and the waist and shoulders were secured by adjustable lap belts and held in position. The right ankle joint was set at 90 deg (with the foot perpendicular to the tibia = 90 deg with angles more than 90 deg being in plantar flexion) with the knee joint at full extension, and the foot was securely strapped to a foot plate connected to the lever arm of the dynamometer (Myoret, Asics, Japan). After that, subjects performed repeated muscle contractions, which consisted of plantar flexion tasks with 2 different contraction modes (concentric and eccentric exercises). Concentric exercises (CON) consisted of forcefully plantar flexing from 70 deg to 115 deg and then relaxing while the attachment was motor-driven to return to 70 deg. Eccentric exercises (ECC) consisted of subjects trying forcefully to maintain plantar flexion throughout the full range of motion while the dynamometer was motor-driven from 115 deg to 70 deg and then relaxing while the attachment was returned passively to 115 deg. Both CON and ECC consisted of 5 sets of 10 maximal voluntary contractions of the plantar flexors at a constant velocity of 15 deg · s − 1, and the rest period between sets was 1 min. The exerted torque (TQ) signal was recorded for each contraction. After repeated muscle contractions, the subject remained relaxed in the same position for 20 min.
Blood circulation of the Achilles tendon
Throughout the experiment, we measured blood circulation (oxyhemoglobin; Oxy, deoxyhemoglobin; Deoxy, total hemoglobin; THb, oxygen saturation; StO2) of the Achilles tendons. To measure blood circulation of the tendon using red laser lights (BOM-L1TRSF, Omega Wave), a probe (SF-DS, Omega Wave, Tokyo, Japan) was positioned 30-mm proximal to the calcaneus. The position of the probe was marked on the skin by small ink dots. These dots ensured the same probe positioning in each test during the experimental period. This instrument uses three red laser lights (635, 650, and 690 nm), and calculates the relative tissue levels of OxyHb, DeoxyHb, and THb. The distance between the light source and photodetector was 5 mm. According to the findings of Kashima , the measurement depth was estimated at 3–5 mm when the dis-
Fig. 1 The mean values of peak torque produced by each contraction of every 10 contractions (1 set) for repeated concentric (open) and eccentric (closed) contractions.
tance between the light source and photodetector was 5 mm. The details of this technique and principles of this instrument have been described elsewhere [9, 13]. Briefly, 2-point detection and the differential calculation method were used for measuring the blood volume and oxygen saturation only in the deep region of the tissue (measurement depth of 3–5 mm; ● ▶ Fig. 1 of Ref . The THb and StO2 at specific depths of tissue could be measured by changing the location of the 2 detectors. The offset value of the blood volume was reduced, and highly sensitive measurements were achieved using the 2-point detection method. In the present study, the units of OxyHb, DeoxyHb, and THb were expressed as µmol/l, although this does not represent the actual physical volume. Tissue StO2 was calculated from OxyHb and THb values using the following formula: StO2 (%) = 100 * OxyHb/THb These data were input onto a personal computer at a sampling frequency of 10 Hz via an A/D transducer (Power Lab, AD Instruments, Australia). The mean values over a given duration (every set during exercises for CON and ECC, every minute over a 20-min of recovery period) were calculated using analytical software (Chart ver. 5.4.2, AD Instruments, Australia). These data were presented as the amount of changes from the resting level. Comparison of the THb, and StO2 values for the Achilles tendon between the two tests (before repeated muscle contractions) revealed no significant differences and a coefficient of variance of 4.8 % and 4.1 % for THb and StO2 of the Achilles tendon, r espectively.
Descriptive data included means ± SD. Two-way (mode × time) ANOVA with repeated measures was used to detect significant differences in the measured variables from the resting level. The F ratios for main effects and interactions were considered significant at p