Prevention of strain‐induced impairments of patellar tendon micromorphology in adolescent athletes

Abstract

High‐level patellar tendon strain may cause impairments of the tendon's micromorphological integrity in growing athletes and increase the risk for tendinopathy. This study investigated if an evidence‐based tendon exercise intervention prevents high‐level patellar tendon strain, impairments of micromorphology and pain in adolescent basketball players (male, 13–15 years). At three time points over a season (M1‐3), tendon mechanical properties were measured using ultrasound and dynamometry, proximal tendon micromorphology with a spatial frequency analysis and pain and disability using VISA‐P scores. The control group (CON, n = 19) followed the usual strength training plan, including sprint and change‐of‐direction drills. In the intervention group (INT, n = 14), three sessions per week with functional exercises were integrated into the training, providing repetitive high‐magnitude tendon loading for at least 3 s per repetition. The frequency of high‐level strain (ie, ≥9%) continuously decreased in INT, while tending to increase in CON since tendon force increased in both (p < 0.001), yet tendon stiffness only in INT (p = 0.004). In CON, tendon strain was inversely associated with tendon peak spatial frequency at all time points (p < 0.05), indicating impairments of tendon micromorphological integrity with higher strain, but not at M2 and M3 in INT. Descriptively, the fraction of asymptomatic athletes at baseline was similar in both groups (~70%) and increased to 100% in M3 in INT, while remaining unchanged in CON. We suggest that functional high‐load tendon exercises could reduce the prevalence of high‐level patellar tendon strain and associated impairments of its micromorphology in adolescent athletes, providing new opportunities for tendinopathy prevention.

Evidence-Based High-Loading Tendon Exercise for 12 Weeks Leads to Increased Tendon Stiffness and Cross-Sectional Area in Achilles Tendinopathy: A Controlled Clinical Trial

“…As the tendon cannot be trained in isolation, the high-loading protocol also leads to adaptations in muscle strength. Plantar flexor MVC increased by 7.2% from PRE to POST in the High-load group, which corresponds to gains to the same high-loading protocol in healthy populations who trained at home with the mobile device (10%, [ 31 ]) or under laboratory conditions on a dynamometer (7%, [ 46 ]). The aforementioned structural adaptations of the Achilles tendon have not been affected or biased by a possible correlation between the leg laterality of the injured leg and the leg laterality of the dominant leg.…”

“…Thus, to counteract phases of enhanced injury risk, a specific tendon training based on the most effective mechanical stimulus should improve the structural integrity of the tendon and thereby reducing injury prevalence. Indeed, high-loading exercise decreased the prevalence of tendon pain in adolescent handball and basketball players [ 30 , 31 ]. Taking the aforementioned into consideration, it seems reasonable to assume that tendinopathy patients in which the tendons tissue integrity has deteriorated may also benefit from high-loading interventions on a structural and clinical level.…”

Mechanical, Material and Morphological Adaptations of Healthy Lower Limb Tendons to Mechanical Loading: A Systematic Review and Meta-Analysis

“…These adaptations alter the mechanical function of the tendon, as a stiffer tendon experiences less strain at a given load and stores more energy at a given strain, and a stronger tendon resists a greater external load prior to failure. Stiffer lower limb tendons are associated with greater rates of force development [11][12][13][14], faster sprint times [15], improved running economy [5,16,17], and reduced risk of tendon damage [18]. Although there is some evidence that strain magnitude and duration are important factors [19][20][21], the mechanical loading stimulus across other loading dimensions (e.g., loading volume, rate, duty cycle) required to induce anabolic tendon adaptation is unclear.…”

Effect of sex on muscle–tendon imbalances and tendon micromorphology in adolescent athletes—A longitudinal consideration

“…Although there is in general a strong association between muscle strength and tendon stiffness, 6 during the last years, studies on adult, 3 adolescent, 4,[10][11][12] and preadolescent athletes 13 reported imbalances in the development of muscle strength and tendon stiffness, leading to increased tendon strain during maximum effort muscle contractions. One consequence of increased tendon strain may be structural impairments within the tendon tissue.…”

“…16 In addition, recent studies from our group provided evidence for an association between high patellar tendon strain levels and a deterioration of the micromorphological structure of the proximal part of the patellar tendon in adolescent athletes. 12,17 Thereby, athletes suffering from tendinopathy and asymptomatic athletes developing tendinopathy demonstrated higher tendon strain and a more disorganized microstructure of the tendon. 17 This supports the idea that tendon strain is an important mechanical factor for tendon damage and overuse.…”