An Identical Twin Study on Human Achilles Tendon Adaptation: Regular Recreational Exercise at Comparatively Low Intensities Can Increase Tendon Stiffness

Achilles tendon adaptation is a key aspect of exercise performance and injury risk prevention. However, much debate exists about the adaptation of the Achilles tendon in response to exercise activities. Most published research is currently limited to elite athletes and selected exercise activities. Also, existing studies on tendon adaptation do not control for genetic variation. Our explorative cross-sectional study investigated the effects of regular recreational exercise activities on Achilles tendon mechanical properties in 40 identical twin pairs. Using a handheld oscillation device to determine Achilles tendon mechanical properties, we found that the Achilles tendon appears to adapt to regular recreational exercise at comparatively low intensities by increasing its stiffness. Active twins showed a 28% greater Achilles tendon stiffness than their inactive twin (p < 0.05). Further, our research extends existing ideas on sport-specific adaptation by showing that tendon stiffness seemed to respond more to exercise activities that included an aerial phase such as running and jumping. Interestingly, the comparison of twin pairs revealed a high variation of Achilles tendon stiffness (305.4–889.8 N/m), and tendon adaptation was only revealed when we controlled for genetic variance. Those results offer new insights into the impact of genetic variation on individual Achilles tendon stiffness, which should be addressed more closely in future studies.Peer Reviewe

The Myometric Assessment of Achilles Tendon and Soleus Muscle Stiffness before and after a Standardized Exercise Test in Elite Female Volleyball and Handball Athletes—A Quasi-Experimental Study

Background: The high prevalence of injuries in female athletes necessitates a course of action that not only enhances research in this field but also incorporates improved prevention programs and regular health monitoring of highly stressed structures such as tendons and muscles. Since myometry is already used by coaches and physiotherapists, it is important to investigate whether tissue stiffness varies in different types of sports, and whether such measures are affected by an acute training session. Methods: Myometric measurements of the Achilles tendon (AT) and soleus muscle (SM) were performed in the longitudinal plane and relaxed tendon position. In total, 38 healthy professional female athletes were examined, applying a quasi-experimental study design, with subgroup analysis performed for different sports. To investigate the stiffness of the AT and SM, 24 female handball and volleyball athletes performed a standardized maximal incremental performance test on a treadmill. In this subgroup, myometric measurements were taken before and after the exercise test. Results: The measurements showed no significant difference between the mean pre- (AT: 661.46 N/m; SM 441.48 N/m) and post-exercise stiffness (AT: 644.71 N/m; SM: 439.07 N/m). Subgroup analysis for different types of sports showed significantly lower AT and SM stiffness in swimming athletes compared to handball (p = 0.002), volleyball (p = 0.000) and hammer throw athletes (p = 0.008). Conclusions: Myometry can be performed on the same day as an acute training session in healthy female professional volleyball and handball athletes. Female swimmers have significantly lower AT and SM stiffness compared to female handball, volleyball and hammer throw athletes. These results show that the stiffness differences in the AT and SM can be assessed by myometry.This research received no external funding.Peer Reviewe

Beiträge zur biomechanischen Charakterisierung faseriger Bindegewebe

Im Mittelpunkt dieser kumulativ angefertigten Arbeit stehen fünf verschiedenartige biomechanische Untersuchungen faseriger Bindegewebe, welche in einer Gesamtschau zusammengeführt werden. Die einzelnen Beiträge setzen sich zusammen aus Untersuchungen zum Einfluss zellulärer Bestandteile auf die mechanischen Eigenschaften faseriger Bindegewebe und die Beeinflussung dieser Ergebnisse durch Messfehler, speziell am Beispiel des Materialschlupfs. Über diese beiden Beiträge wird eine Verbindung hergestellt zur rechnergestützten Simulation der Wirkung eines Beckenkompressionsgurts auf die Bänder des Beckenrings und dem Transmissionsverhalten faseriger Bindegewebe bei Zugbelastung. Im fünften Beitrag wird am Beispiel des Zusammenwirkens von Achillessehne, Fersenfettpolster und Plantarfaszie in vitro die Komplexität der Betrachtung faseriger Bindegewebe aufgezeigt. Die Zusammenführung der einzelnen Untersuchungen wird begleitet von der Frage, ob die bestehenden biomechanischen Untersuchungsansätze ausreichend sind, um ein umfassendes Verständnis zur funktionellen Bedeutung faseriger Bindegewebe aufbauen zu können

Evolutionary anatomy of the plantar aponeurosis in primates, including humans

The plantar aponeurosis in the human foot has been extensively studied and thoroughly described, in part, because of the incidence of plantar fasciitis in humans. It is commonly assumed that the human plantar aponeurosis is a unique adaptation to bipedalism that evolved in concert with the longitudinal arch. However, the comparative anatomy of the plantar aponeurosis is poorly known in most mammals, even among non-human primates, hindering efforts to understand its function. Here, we review previous anatomical descriptions of 40 primate species and use phylogenetic comparative methods to reconstruct the evolution of the plantar aponeurosis and its relationship to the plantaris muscle in primates. Ancestral state reconstructions suggest that the overall organization of the human plantar aponeurosis is shared with chimpanzees and that a similar anatomical configuration evolved independently in different primate clades as an adaptation to terrestrial locomotion. The presence of a plantar aponeurosis with clearly developed lateral and central bands in the African apes suggests that this structure is not prohibitive to suspensory locomotion and that these species possess versatile feet adapted for both terrestrial and arboreal locomotion. This plantar aponeurosis configuration would have been advantageous in enhancing foot stiffness for bipedal locomotion in the earliest hominins, prior to the evolution of a longitudinal arch. Hominins may have subsequently evolved thicker and stiffer plantar aponeuroses alongside the arch to enable a windlass mechanism and elastic energy storage for bipedal walking and running, although this idea requires further testing

Effect of the upward curvature of toe springs on walking biomechanics in humans

Although most features of modern footwear have been intensively studied, there has been almost no research on the effects of toe springs. This nearly ubiquitous upward curvature of the sole at the front of the shoe elevates the toe box dorsally above the ground and thereby holds the toes in a constantly dorsiflexed position. While it is generally recognized that toe springs facilitate the forefoot’s ability to roll forward at the end of stance, toe springs may also have some effect on natural foot function. This study investigated the effects of toe springs on foot biomechanics in a controlled experiment in which participants walked in specially-designed sandals with varying curvature in the toe region to simulate toe springs ranging from 10 to 40 degrees of curvature. Using inverse dynamics techniques, we found that toe springs alter the joint moments and work at the toes such that greater degrees of toe spring curvature resulted in lower work requirements during walking. Our results help explain why toe springs have been a pervasive feature in shoes for centuries but also suggest that toe springs may contribute to weakening of the foot muscles and possibly to increased susceptibility to common pathological conditions such as plantar fasciitis

Integrating a Potentiometer into a Knee Brace Shows High Potential for Continuous Knee Motion Monitoring

Continuous monitoring of knee motion can provide deep insights into patients’ rehabilitation status after knee injury and help to better identify their individual therapeutic needs. Potentiometers have been identified as one possible sensor type for continuous monitoring of knee motion. However, to verify their use in monitoring real-life environments, further research is needed. We aimed to validate a potentiometer-embedded knee brace to measure sagittal knee kinematics during various daily activities, as well as to assess its potential to continuously monitor knee motion. To this end, the sagittal knee motion of 32 healthy subjects was recorded simultaneously by an instrumented knee brace and an optoelectronic reference system during activities of daily living to assess the agreement between these two measurement systems. To evaluate the potentiometer’s behavior during continuous monitoring, knee motion was continuously recorded in a subgroup (n = 9) who wore the knee brace over the course of a day. Our results show a strong agreement between the instrumented knee brace and reference system across all investigated activities as well as stable sensor behavior during continuous tracking. The presented potentiometer-based sensor system demonstrates strong potential as a device for measuring sagittal knee motion during daily activities as well as for continuous knee motion monitoring

Impact of Obesity on Foot Kinematics: Greater Arch Compression and Metatarsophalangeal Joint Dorsiflexion despite Similar Joint Coupling Ratios

This study investigates the sagittal plane dynamics of the foot, particularly the metatarsophalangeal (MTP) joint and medial longitudinal arch (MLA) movements, in relation to obesity and foot health. The kinematics of the MTP and arch joints were measured in 17 individuals with class 2–3 obesity (BMI > 35 kg/m²) and 10 normal-weight individuals (BMI ≤ 24.9 kg/m²) using marker-based tracking. Analysis was conducted during heel lifting while seated and during walking at self-selected speeds. The results indicated that obese participants exhibited 20.92% greater MTP joint dorsiflexion at the end of the push-off phase and 19.84% greater MLA compression during the stance phase compared to normal-weight controls. However, no significant differences were found in the kinematic joint coupling ratio. While these findings reveal the different biomechanical behaviors of the MTP joint and MLA in obese compared to normal-weight individuals, it is important to interpret the implications of these differences with caution. This study identifies specific biomechanical variations that could be further explored to understand their potential impact on foot health in obese populations

Pelvic belt effects on pelvic morphometry, muscle activity and body balance in patients with sacroiliac joint dysfunction.

The sacroiliac joint (SIJ) is frequently involved in low back and pelvic girdle pain. However, morphometrical and functional characteristics related to SIJ pain are poorly defined. Pelvic belts represent one treatment option, but evidence still lacks as to their pain-reducing effects and the mechanisms involved. Addressing these two issues, this case-controlled study compares morphometric, functional and clinical data in SIJ patients and healthy controls and evaluates the effects of short-term pelvic belt application.Morphometric and functional data pertaining to pelvic belt effects were compared in 17 SIJ patients and 17 controls. Lumbar spine and pelvis morphometries were obtained from 3T magnetic resonance imaging. Functional electromyography data of pelvis and leg muscles and center of pressure excursions were measured in one-leg stance. The numerical rating scale was used to evaluate immediate pain-reducing effects.Pelvic morphometry was largely unaltered in SIJ patients and also by pelvic belt application. The angle of lumbar lateral flexion was significantly larger in SIJ patients without belt application. Muscle activity and center of pressure were unaffected by SIJ pain or by belt application in one-leg stance. Nine of 17 patients reported decreased pain intensities under moderate belt application, four reported no change and four reported increased pain intensity. For the entire population investigated here, this qualitative description was not confirmed on a statistical significant level.Minute changes were observed in the alignment of the lumbar spine in the frontal plane in SIJ patients. The potential pain-decreasing effects of pelvic belts could not be attributed to altered muscle activity, pelvic morphometry or body balance in a static short-term application. Long-term belt effects will therefore be of prospective interest

Pelvic belt effects on pelvic morphometry, muscle activity and body balance in patients with sacroiliac joint dysfunction

The sacroiliac joint (SIJ) is frequently involved in low back and pelvic girdle pain. However, morphometrical and functional characteristics related to SIJ pain are poorly defined. Pelvic belts represent one treatment option, but evidence still lacks as to their pain-reducing effects and the mechanisms involved. Addressing these two issues, this case-controlled study compares morphometric, functional and clinical data in SIJ patients and healthy controls and evaluates the effects of short-term pelvic belt application