ABSTRACT
Previous research suggests that the moment arm of the m. triceps surae tendon (i.e., Achilles tendon), is positively correlated with the energetic cost of running. This relationship is derived from a model which predicts that shorter ankle moment arms place larger loads on the Achilles tendon, which should result in a greater amount of elastic energy storage and return. However, previous research has not empirically tested this assumed relationship. We test this hypothesis using an inverse dynamics approach in human subjects (n = 24) at speeds ranging from walking to sprinting. The spring function of the Achilles tendon was evaluated using specific net work, a metric of mechanical energy production versus absorption at a limb joint. We also combined kinematic and morphological data to directly estimate tendon stress and elastic energy storage. We find that moment arm length significantly determines the spring-like behavior of the Achilles tendon, as well as estimates of mass-specific tendon stress and elastic energy storage at running and sprinting speeds. Our results provide support for the relationship between short Achilles tendon moment arms and increased elastic energy storage, providing an empirical mechanical rationale for previous studies demonstrating a relationship between calcaneal length and running economy. We also demonstrate that speed and kinematics moderate tendon performance, suggesting a complex relationship between lower limb geometry and foot strike pattern.
Subject(s)
Achilles Tendon/physiology , Energy Metabolism , Heel/physiology , Muscle, Skeletal/physiology , Running , Walking , Achilles Tendon/anatomy & histology , Achilles Tendon/diagnostic imaging , Biomechanical Phenomena , Heel/anatomy & histology , Heel/diagnostic imaging , Humans , Muscle, Skeletal/anatomy & histology , Muscle, Skeletal/diagnostic imaging , UltrasonographyABSTRACT
BACKGROUND: Isobaric gasless laparoscopy and minilaparotomy have been used as more recent minimally invasive approaches to myomectomy. This randomized trial aimed to compare the surgical and immediate postoperative outcomes for myomectomy performed by isobaric gasless laparoscopy with those for minilaparotomy. METHODS: A total of 100 patients with symptomatic uterine myomas requiring myomectomy were randomly allocated to the gasless laparoscopy group or the minilaparotomy group. The randomization procedure was based on a computer-generated list. The primary outcome was a comparison of the discharge times between the two procedures. A power calculation verified that more than 26 patients for each group was necessary to detect a difference of more than 24 h in discharge time with an alpha error level of 5% and a beta error of 80%. Continuous outcome variables were analyzed using the Student's t-test. Discrete variables were analyzed with the chi-square test or Fisher's exact test. A p value less than 0.05 was considered statistically significant. RESULTS: The mean discharge time was longer for minilaparotomy than for gasless laparoscopy (98.4 +/- 1.4 vs 52.8 +/- 1.6 h; p < 0.001). Gasless laparoscopy resulted in shorter times for canalization (21.6 +/- 1.1 vs 32 +/- 1.3 h; p < 0.05) and surgery (79.5 +/- 25.1 vs 103.5 +/- 24.9 min; p < 0.001). The intraoperative blood loss was less with gasless laparoscopy (154.2 +/- 1.2 vs 188.6 +/- 1.3 ml; p < 0.001). No intraoperative complications occurred, and no case was returned to the theater in either group. No conversion to standard laparotomy was necessary. CONCLUSIONS: Isobaric gasless laparoscopy and minilaparotomy can be suitable options for uterine myomectomy. Several surgical and immediate postoperative outcomes were significantly better in the gasless laparoscopy group than in the minilaparotomy group. However, further controlled prospective studies are required to confirm the results.
