Toshihiro Ikebukuro

Time Course of Changes in Muscle and Tendon Properties During Strength Training and Detraining

Kubo, K, Ikebukuro, T, Yata, H, Tsunoda, N, and Kanehisa, H. Time course of changes in muscle and tendon properties during strength training and detraining. J Strength Cond Res 24(2): 322-331, 2010-The purpose of this study was to investigate the time course of changes in mechanical and morphological properties of muscle and tendon during isometric training and detraining. Eight subjects completed 3 months of isometric knee extension training and detraining for another 3 months. At beginning and on every 1 month of training and detraining periods, muscle strength, neural activation level, muscle and tendon cross-sectional areas (CSA), and tendon stiffness were measured. Training increased muscle strength and neural activation level by 29.6 and 7.3% after 2 months and by 40.5 and 8.9% after 3 months (all ps < 0.05). Muscle CSA and tendon stiffness did not change until 2 months of training period, and afterward, the increases in muscle CSA and tendon stiffness reached statistical significance at the end of training period (both ps < 0.05). During detraining period, muscle strength and neural activation level did not change, although muscle CSA and tendon stiffness decreased to pre-training level at 1 and 2 months of detraining, respectively. These results suggest that the adaptations of tendon properties and muscle morphology to resistance training are slower than those of muscle function and inversely that the adaptations of former to detraining are faster than those of latter.

Effects of static and dynamic training on the stiffness and blood volume of tendon in vivo

The purpose of this study was to investigate the effects of static and dynamic training on the stiffness and blood volume of the human tendon in vivo. Ten subjects completed 12 wk (4 days/wk) of a unilateral training program for knee extensors. They performed static training on one side [ST; 70% of maximum voluntary contraction (MVC)] and dynamic training on the other side (DT; 80% of one repetition maximum). Before and after training, MVC, neural activation level (by interpolated twitch), muscle volume (by magnetic resonance imaging), stiffness of tendon-aponeurosis complex and patella tendon (by ultrasonography), and blood volume of patella tendon (by red laser lights) were measured. Both protocols significantly increased MVC (49% for ST, 32% for DT; both P < 0.001), neural activation level (9.5% for ST, 7.6% for DT; both P < 0.01), and muscle volume (4.5% for ST, 5.6% for DT; both P < 0.01). The stiffness of tendon-aponeurosis complex increased significantly after ST (55%; P = 0.003) and DT (30%; P = 0.033), while the stiffness of patella tendon increased significantly after ST (83%; P < 0.001), but not for DT (P = 0.110). The blood volume of patella tendon increased significantly after DT (47%; P = 0.016), but not for ST (P = 0.205). These results implied that the changes in the blood volume of tendon would be related to differences in the effects of resistance training on the tendon properties.

Noninvasive measures of blood volume and oxygen saturation of human Achilles tendon by red laser lights

Aim:  Spectroscopic measurement using near‐infrared spectroscopy and red laser lights was performed to investigate the blood volume (total haemoglobin; THb) and oxygen saturation (oxygenated haemoglobin saturation; StO2) of the human Achilles tendon during single and repetitive isometric contractions.

Changes in Blood Circulation of the Contralateral Achilles Tendon During and After Acupuncture and Heating

The purpose of this study was to investigate the effects of acupuncture and heating (application of hot pack) treatments on blood circulation in the contralateral Achilles tendon. During the treatments (10 min for acupuncture, 20 min for heating) and recovery period (40 min), the blood volume (THb) and oxygen saturation (StO2) of the treated and the non-treated tendons were measured using red laser lights. During both treatments, THb and StO2 of the treated tendon increased significantly from the resting level. The increased THb and StO2 of the treated tendon were maintained until the end of the recovery period after removal of the acupuncture needle, although these values decreased after removal of the hot pack. Although THb of the non-treated sides did not change during both acupuncture and heating treatments, it increased gradually after removal of the acupuncture needle or the hot pack. For both treatments, the amount of increase in THb of the non-treated tendon was significantly correlated to that of the treated tendon during the last phase of recovery period. These results obtained from the healthy subjects imply that blood circulation in the injured tendon in a plaster cast may be improved by applying acupuncture or heating treatments to the contralateral healthy limb.

Tendon properties and muscle architecture for knee extensors and plantar flexors in boys and men

BACKGROUND The purpose of this study was to compare the elastic properties and size of tendinous structures and muscle architecture for knee extensors and plantar flexors in boys and men. METHODS Twenty-two early pubescent boys (9.6-12.7yrs) and 23 young adult men (19.8-26.2yrs) participated in this study. The maximal strain and thickness of tendinous structures for knee extensors and plantar flexors were measured using ultrasonography. In addition, the fascicle lengths of vastus lateralis and medial gastrocnemius muscles were measured. FINDINGS The maximal strain of tendinous structures for plantar flexors was significantly greater in boys than in men, while there was no difference in the maximal strain for knee extensors between the two groups. The relative thickness (to body mass(1/3)) of Achilles tendon was significantly greater in boys than in men, although there was no difference in that of patellar tendon between the two groups. The relative fascicle length (to limb length) of vastus lateralis muscle was significantly lower in boys than in men, although there was no difference in that of medial gastrocnemius muscle between the two groups. INTERPRETATION These results suggest that the amount of changes in the elastic properties and sizes of tendinous structures and in the fascicle lengths from early pubescence to maturity is different for different muscle groups (in particular, the knee extensors and the plantar flexors).

Effects of different duration contractions on elasticity, blood volume, and oxygen saturation of human tendon in vivo

The present study aimed to investigate changes in elasticity, blood volume, and oxygen saturation of tendon caused by repeat contractions of different durations. Eight male subjects performed endurance tests, which consisted of isometric plantar flexion with two different durations: a shorter contraction (SC) and a longer contraction (LC). During endurance tests and a recovery period, we measured the total hemoglobin (THb) and oxygen saturation (StO2) of the medial gastrocnemius muscle and Achilles tendon using near infrared spectroscopy and red laser lights. In addition, elongation of the Achilles tendon during the endurance test was measured via ultrasonography. Compared to the resting level, the THb and StO2 of the tendon increased significantly after SC, but not after LC. On the other hand, Achilles tendon became more compliant after LC, but not after SC. These results suggested that duration of contraction affected not only elasticity, but also blood volume and oxygen saturation of tendons.

Blood Circulation of Patellar and Achilles Tendons during Contractions and Heating.

PURPOSE Recent studies using ultrasonography have demonstrated that training-induced changes in the mechanical properties of tendons in plantar flexors (i.e., Achilles tendon) are lower than those in knee extensors (i.e., patellar tendon). However, the mechanisms for these phenomena are unknown. The purpose of this study was to compare changes in blood circulation of patellar and Achilles tendons by repeated muscle contractions and heating. METHODS Eleven healthy males participated in this study. During and after repeated muscle contractions (50 repetitions at 50% of the isometric maximum voluntary contraction for 3 s with 3-s relaxations) and heating (20 min), blood volume (total hemoglobin (THb)) and oxygen saturation (StO2) of the patellar and Achilles tendons were measured using red laser lights. RESULTS During repeated muscle contractions, StO2 of the patellar tendon decreased significantly, but that of the Achilles tendon did not. During heating, THb and StO2 increased significantly for both tendons. Increases in THb and StO2 of the patellar tendon were significantly higher than those of the Achilles tendon (both P < 0.001). CONCLUSION These results demonstrated that changes in blood circulation of the patellar tendon during exercise and heating were higher than those of the Achilles tendon. This result appears to be related to the differences in the plasticity of the mechanical properties of the patellar and Achilles tendons.

A Longitudinal Assessment of Running Economy and Tendon Properties in Long-distance Runners

Kubo, K, Tabata, T, Ikebukuro, T, Igarashi, K, and Tsunoda, N. A longitudinal assessment of running economy and tendon properties in long-distance runners. J Strength Cond Res 24(7): 1724-1731, 2010-The aim of this study was to investigate longitudinal changes in tendon properties and running economy of long-distance runners (LDRs) in the preparatory periods of track season (TS) and road season (RS). Eleven well-trained LDRs and 6 untrained subjects participated in the present study. In each period, muscle strength, neural activation level, and tendon elongation for both knee extensors and plantar flexors, jump performances, and oxygen consumption during submaximal running velocities were measured. No significant differences observed in any measured variables between the 2 seasons for untrained subjects. For LDRs, the total running distance during 1 month preceding RS (832 ± 95 km) was significantly longer than that during 1 month preceding TS (718 ± 80 km). No significant differences in the muscle strength, neural activation level, and jump performances were found between TS and RS. The stiffness of tendon structures in RS was significantly lower than those in TS for both knee extensors (-14.4%, p = 0.023) and plantar flexors (-16.6%, p = 0.040). At 3 running velocities, the oxygen consumptions in RS were significantly lower than those in TS. These results suggested that the lower oxygen consumption during submaximal running velocities observed in the preparatory period of RS may be attributable to the more compliant tendon structures but not in the neuromuscular characteristics.

Active muscle and tendon stiffness of plantar flexors in sprinters

ABSTRACT The aim of the present study was to investigate and compare muscle and tendon stiffness under active conditions in sprinters and untrained participants. In total, 14 sprinters and 24 untrained men participated in this study. Active muscle stiffness in the medial gastrocnemius muscle was calculated based on changes in estimated muscle force and fascicle length during fast stretching after submaximal isometric contractions. Tendon stiffness was determined during isometric plantar flexion using ultrasonography. No significant differences were observed in active muscle stiffness between sprinters and untrained men at any torque levels. Furthermore, no significant difference was noted in tendon stiffness between the two groups. These results suggest that muscle and tendon mechanical properties in the plantar flexors under active conditions are similar in sprinters and untrained participants.

Changes in Bone Alkaline Phosphatase and Procollagen Type-1 C-Peptide After Static and Dynamic Exercises

We investigated the effects of two types of nonweight-bearing exercise on changes in bone-specific alkaline phosphatase (BAP) and procollagen type 1 C-peptide (P1P). BAP is a specific marker of bone synthesis, whereas P1P reflects synthesis of type 1 collagen in other organs as well as bone. Eight participants performed static and dynamic unilateral knee extensions. BAP and P1P were measured before, and at 1, 2, 24, 48, and 72 hr after exercise. P1P increased at 24 hr after a static knee extension exercise, whereas BAP did not change during the experimental period. We found no changes in these markers after dynamic exercise. These results imply that type 1 collagen synthesis in tendons increases after static exercise.