Muscle‐tendon morphology and function following long‐term exposure to repeated and strenuous mechanical loading

Abstract

We mapped structural and functional characteristics of muscle‐tendon units in a population exposed to very long‐term routine overloading. Twenty‐eight military academy cadets (age = 21.00 ± 1.1 years; height = 176.1 ± 4.8 cm; mass = 73.8 ± 7.0 kg) exposed for over 24 months to repetitive overloading were profiled via ultrasonography with a senior subgroup of them (n = 11; age = 21.4 ± 1.0 years; height = 176.5 ± 4.8 cm; mass = 71.4 ± 6.6 kg) also tested while walking and marching on a treadmill. A group of eleven ethnicity‐ and age‐matched civilians (age = 21.6 ± 0.7 years; height = 176.8 ± 4.3 cm; mass = 74.6 ± 5.6 kg) was also profiled and tested. Cadets and civilians exhibited similar morphology (muscle and tendon thickness and cross‐sectional area, pennation angle, fascicle length) in 26 out of 29 sites including the Achilles tendon. However, patellar tendon thickness along the entire tendon was greater (P < .05) by a mean of 16% for the senior cadets compared with civilians. Dynamically, cadets showed significantly smaller ranges of fascicle length change and lower shortening velocity in medial gastrocnemius during walking (44.0% and 47.6%, P < .05‐.01) and marching (27.5% and 34.3%, P < .05‐.01) than civilians. Furthermore, cadets showed lower normalized soleus electrical activity during walking (22.7%, P < .05) and marching (27.0%, P < .05). Therefore, 24‐36 months of continuous overloading, primarily occurring under aerobic conditions, leads to more efficient neural and mechanical behavior in the triceps surae complex, without any major macroscopic alterations in key anatomical structures.

Functional and morphological changes in shoulder girdle muscles after repeated climbing exercise

“…Repetitive mechanical overload has been described as the main factor causing muscle-tendon morphology and altering motor functions (Bissas et al, 2020;Pozzi et al, 2021). An increased thickness of the supraspinatus tendon might be the first symptom of repetitive loading related to shoulder pain (Pozzi et al, 2021), and may lead to occupy a greater portion of the subacromial space (Michener et al, 2015).…”

Morphological and mechanical properties of lower limbs in competitive racewalkers: Associations with performance

“…A 40-mm linear array probe (12-18 MHz) was used to collect longitudinal-and transverse-plane images of AT. The probe was placed 40 mm proximal to the calcaneal notch (approximated using ultrasound) to obtain thickness and CSA measurements (Bissas et al, 2020). For each site, a minimum of three scans were analyzed.…”

Employing body-fixed sensors and machine learning to predict physical activity in military personnel

“…Uphill walking reflects a daily stimulus imposed on the infantry population of this study who predominately march on rough terrains with gradient as part of their occupational training and service. As recently demonstrated12 such exposure to prolonged aerobic overloading results in neuromechanical modifications in the lower extremities of infantry soldiers compared to civilian populations of similar age. These modifications enhance the ability to perform occupation-specific and routine locomotion tasks at a lower muscle mechanical and neural cost, resulting in a movement characterized by lower amplitude of dynamic muscle actions in the triceps surae complex.…”

“…These modifications enhance the ability to perform occupation-specific and routine locomotion tasks at a lower muscle mechanical and neural cost, resulting in a movement characterized by lower amplitude of dynamic muscle actions in the triceps surae complex. Whether this unique mechanical behaviour has a relationship with the way our sensor and ML techniques detect gait remains unknown but as this study's sample came from the same military population as for that study12 it is worth noting the strength of the present study to include authentic military samples already conditioned to routine military activities.…”