ECSS Paris 2023: CP-BM04
INTRODUCTION: Achilles tendon (AT) stiffness is a key factor in athletic performance, particularly in high-impact sports such as basketball. Athletes generally exhibit higher AT stiffness than the general population, which can enhance force transmission and movement efficiency but may also increase injury risk if not balanced with adequate strength and control. Shear-wave elastography (SWE) has been used to assess AT stiffness, yet the relationship between AT stiffness, performance, range of motion (ROM), and injury in university athletes remains unclear. This study aimed to investigate these relationships in male and female university varsity basketball players. METHODS: Thirty-two university level varsity basketball athletes (12 females, 20 males) participated in this cross-sectional study. SWE was used to assess AT stiffness in both the preferred takeoff leg (PTL) and non-preferred takeoff leg (NPTL). Functional assessments included a single-leg vertical jump, heel raise test, and ankle dorsiflexion ROM. Participants also completed questionnaires on demographics, injury history, and Victorian Institute of Sport Assessment-Achilles (VISA-A) scores. Testing was conducted in a standardized manner pre-training. Paired t-tests compared AT stiffness between PTL and NPTL, while independent t-tests examined differences in AT stiffness and asymmetry between athletes with and without a recent history of lower body injury. Pearson correlations were used to assess relationships between AT stiffness, performance, and ROM. RESULTS: Mean AT stiffness was 455.4 ± 72.4 kPa in male athletes and 411.7 ± 48.5 kPa in female athletes (p = 0.185). No significant differences in AT stiffness were observed between PTL and NPTL in either males (448.2 ± 83.6 kPa vs. 462.6 ± 84.6 kPa) or females (407.9 ± 40.0 kPa vs. 415.5 ± 77.3 kPa). Male athletes who had sustained a lower body injury in the previous 12 months exhibited significantly lower AT stiffness than non-injured males (p = 0.040), while female athletes with a recent lower body injury displayed lower between-limb stiffness asymmetry compared to their healthy counterparts (p = 0.027). No significant correlations were found between AT stiffness and performance measures or ROM in either sex. CONCLUSION: This study found no significant differences in AT stiffness between the PTL and NPTL or between male and female basketball athletes. However, male athletes with a recent history of injury demonstrated significantly lower AT stiffness, while female athletes with a recent injury exhibited reduced side-to-side stiffness asymmetry. Our findings suggest that injury history may influence AT stiffness, however, AT stiffness was not associated with functional performance or ROM in our sample of university level basketball players. Further research is warranted to explore the long-term implications of AT stiffness variations on injury risk and athletic performance.
Read CV Owen SoontjensECSS Paris 2023: CP-BM04
INTRODUCTION: During the contact phase of running, the visco-elastic properties of the muscle-tendon complex (MTC) play a crucial role in functional muscle-tendon interaction and the recycling of elastic energy [1].In recent years, the use of thick-soled shoes in track and field events has led to improvements in running efficiency and competition records, but the effects of these shoes on the mechanical properties of the lower leg system, including MTC, are still unclear in many cases. In addition, the effects of the muscle force exerted by changes in running speed are also unknown. The purpose of this study was to clarify these changes experimentally. METHODS: Eight male and female subjects participated in the study. The viscoelastic properties of the MTC were measured using the vibration method under multiple load settings (similar to Fukashiro et al. [2]). The subject was placed in a seated position (ankle and knee joints 90deg), with the ball of the foot on a force plate edge. A weight was placed on the knee, and with the posture maintained by isometric contraction (the muscle force exerted was varied), the damped oscillation of the triceps surae muscle was induced. The waveforms were regressed by the least-squares method on the following equation to calculate the unknowns, gamma (𝛾), omega(𝜔), 𝑎c, 𝑎𝑠 and M. 𝐹(𝑡)=e^−𝛾𝑡 (𝑎c𝑐𝑜𝑠𝜔𝑡+𝑎𝑠𝑠𝑖𝑛𝜔𝑡)+Mg where F is force, t is time, e is Napier number, 𝛾 is damping factor, a is amplitude, 𝜔 is angular frequency, M is effective mass, and g is gravitational acceleration. Then, after consideration of the moment arm of muscle, the elastic and viscous coefficients (k and b) of MTC were calculated. k＝M(𝜔^2+𝛾^2) b=2M𝛾 These measurements were taken in three conditions: barefoot (S0), conventional running shoes (S1), and thick-soled shoes (S2). RESULTS: Elastic coefficients: k increased significantly with force increment in all shoes. k of S1 was greater than that of S0 in all force application conditions. S2 showed almost the same value as S1 up to 300N, but after that k decreased, and at 600N it was smaller than S0. Viscosity coefficient: b increased significantly with force application up to 300N for all shoes. The change trends for S0 and S1 were similar, but S2 showed much lower b than the other two conditions after 300N. In addition, the individual differences due to different shoes on both coefficients were substantial. CONCLUSION: It was suggested that the effect of the shoes on the viscoelasticity of the lower leg system was related to the exerted muscle force, or, in other words, the strength of the kick during the contact phase of running. The effect of these shoes could be related to the intrinsic viscoelasticity of MTC in subjects. References [1] Roberts and Azizi. J Exp Biol. 214: 353-61, 2011. [2] Fukashiro et al. Acta Physiol Scand. 175, 183-87, 2002.
Read CV Toshiaki OdaECSS Paris 2023: CP-BM04
INTRODUCTION: When the knee is flexed, during plantarflexion the gastrocnemius muscles contribution to ankle torque is reduced. Literature reports are inconsistent whether soleus (SOL) compensates for this reduced gastrocnemius function. Therefore, the aim of this study was to investigate SOL fascicle behavior during plantarflexion with the knee flexed vs. knee extended. We hypothesize that the compensation of the soleus muscle is evident when the knee joint is flexed. However, we assume that at high angular velocities, the compensation of the soleus muscle is not significantly affected by changes in knee joint angle. METHODS: Healthy physically active Chinese male university students (n=17) performed knee-flexed (90°) and knee-extended (180°) plantarflexions at 60°·s-1 and 120°·s-1 on an isokinetic dynamometer. During the measurements, electromyographic activity of the medial gastrocnemius (MG) and SOL were recorded with bipolar surface electrodes, and the fascicle behavior of these muscles were obtained by ultrasonography. RESULTS: Plantarflexion peak torque performed with the knee flexed vs. knee extended was lower by 44% at 60°·s⁻¹ (p < 0.001) and 18% at 120°·s⁻¹ (p = 0.0001). SOL EMG activity was higher in knee-flexed plantarflexion by 44.9% at 60°·s-1 and by 21.6% at 120°·s-1. As expected, MG activity was lower in knee-flexed plantarflexion at both velocities (22.9 ±9.8%at 60°·s⁻¹ vs 67.6±12.3 %at 120°·s⁻¹, p = 0.005). MG fascicles operated at shorter fascicle length (14.3±0.6% at 60°·s⁻¹ vs 46.7±0.6% at 120°·s⁻¹, p > 0.005) in knee-flexed vs. knee-extended plantarflexion. Knee joint position did not affect SOL fascicle shortening. CONCLUSION: Consistent with previous literature, our findings indicate that a flexed knee joint position alters medial gastrocnemius (MG) fascicle behavior and activation patterns. Although the SOL exhibited higher electrical activity at lower contraction velocities in the knee-flexed position, this did not correlate with distinct fascicle behavior, and the differences were minimal at higher contraction velocities. Consequently, we cannot directly confirm that SOL compensates for reduced MG function during knee-flexed plantarflexion. Additionally, while EMG activity demonstrated statistical significance, muscle fiber performance did not, suggesting that changes in knee joint position increase muscle activation without providing definitive evidence of SOL compensation.
Read CV Jingyi YeECSS Paris 2023: CP-BM04