The menstrual cycle is an important biological rhythm, whereby large cyclic fluctuations in endogenous sex hormones, such as estrogen and progesterone, are observed, which can affect performance. Evidence shows that endogenous and exogenous changes in hormone concentrations during the menstrual cycle exert many effects on the nervous and endocrine systems, in addition to the connective tissue, with consequences for the movement system. Pre-clinical studies (i.e., in animal models) show an estrogen association with the structural and mechanical properties of tendons and ligaments. Several elegant studies performed with female participants have tried to establish the mechanism underlying the effect of estrogen on collagen synthesis and its effects on exercise and functionality. Their findings suggest that the tendon properties may be affected when exposed to varying concentrations of estrogen. The largest tendon in humans, the Achilles tendon, has a direct role in functional capacity, activities of daily living, and locomotion. Studies show that the triceps surae's structural and mechanical properties may change throughout the menstrual cycle, and that these changes are related to endogenous and exogenous fluctuations in estrogen and progesterone. Musculotendinous stiffness, which is dependent on the collagen content, has been seen to vary considerably over the course of the menstrual cycle. In addition, it has been reported that females who have been taking the contraceptive pill for at least a year demonstrate lower levels of tendon strain compared to non-pill taking females, indicating a possible influence of hormonal state on tendon mechanical properties. However, the different experimental designs, the varied approaches to the evaluations and the lack of studies with high methodological quality limit our understanding of the effects of the different phases of the menstrual cycle on the triceps surae's neuromechanical properties. The aim of this observational study will be to investigate whether the morphological, mechanical (active and passive), material, and functional properties of the plantar flexor muscles and of the Achilles tendon, as well as functional parameters, change during voluntary contractions throughout the phases of the menstrual cycle in eumenorrheic women and in users of hormonal contraception. Understanding the acute effects of these properties in eumenorrheic women and users of hormonal contraception is essential so that we can adequately plan interventions and prescriptions of physical exercise and rehabilitation aimed for women.
Study Type
OBSERVATIONAL
Enrollment
40
Monitoring assessments to verify the effect of different phases of the menstrual cycle on the neuromechanical properties of the Achilles tendon.
Marco Aurelio Vaz
Porto Alegre, Brazil
RECRUITINGMaximal voluntary isometric contraction (Nm)
Maximal voluntary isometric contraction (MVIC) of the plantar flexor muscles, i.e., largest plantar flexor torque generated in different phases of menstrual cycle and different moments of contraception use
Time frame: The assessment will be performed at the beginning (1-4 days), middle (10-14 days), and end (22-26 days) of Cycle 1 (each menstrual cycle is between 28-30 days).
Achilles tendon stiffness (N/mm)
Achilles tendon stiffness will be calculated during maximal voluntary contraction in different phases of menstrual cycle and contraception users
Time frame: The assessment will be performed at the beginning (1-4 days), middle (10-14 days), and end (22-26 days) of Cycle 1 (each menstrual cycle is between 28-30 days).
Cross-sectional area (mm²)
The evaluation of the cross-sectional area will be carried out using ultrasound, evaluating proximal, medial and distal portions from the calcaneus bone.
Time frame: The assessment will be performed at the beginning (1-4 days), middle (10-14 days), and end (22-26 days) of Cycle 1 (each menstrual cycle is between 28-30 days).
tendon stress (MPa) during maximal voluntary contractions
The stress will be obtained by taking the ratio between Achilles tendon strength and tendon cross sectional area, and tension taking the relationship between tendon elongation and tendon length at rest
Time frame: The assessment will be performed at the beginning (1-4 days), middle (10-14 days), and end (22-26 days) of Cycle 1 (each menstrual cycle is between 28-30 days).
Myotendinous junction displacement (mm)
The displacement of the myotendinous junction of the medial gastrocnemius muscle (DTJM) will be evaluated during passive torque assessment.The analysis will be carried out in three core cycles of the five passive torque cycles.
Time frame: The assessment will be performed at the beginning (1-4 days), middle (10-14 days), and end (22-26 days) of Cycle 1 (each menstrual cycle is between 28-30 days).
Ankle functionality (cm)
Ankle functionality and ankle dorsiflexion range of motion assessed through functional heel raise theses.
Time frame: The assessment will be performed at the beginning (1-4 days), middle (10-14 days), and end (22-26 days) of Cycle 1 (each menstrual cycle is between 28-30 days).
Blood concentrations (pg/ml)
Blood concentrations of estrogen and progesterone in different phases of menstrual cycle
Time frame: The assessment will be performed at the beginning (1-4 days), middle (10-14 days), and end (22-26 days) of Cycle 1 (each menstrual cycle is between 28-30 days).
Transvaginal ultrasound (cm)
Transvaginal ultrasound will be evaluated to control the menstrual cycle and take measurements of the ovary and uterus in the different phases of the menstrual cycle.
Time frame: The assessment will be performed at the beginning (1-4 days), middle (10-14 days), and end (22-26 days) of Cycle 1 (each menstrual cycle is between 28-30 days).
Tendon length (mm²)
The length of the tendon will be assessed using ultrasound, starting from the myotendinous junction to the calcaneus bone. The measurement will be carried out with a measuring tape.
Time frame: The assessment will be performed at the beginning (1-4 days), middle (10-14 days), and end (22-26 days) of Cycle 1 (each menstrual cycle is between 28-30 days).
Strain (%) during maximal voluntary contractions
strain will be evaluated through the relationship relationship between tendon deformation and tendon length at rest. ratio between tendon elongation and TL at rest.
Time frame: The assessment will be performed at the beginning (1-4 days), middle (10-14 days), and end (22-26 days) of Cycle 1 (each menstrual cycle is between 28-30 days).
Hysteresis (%)
Hysteresis measurements will be obtained from five cycles, but they will begin at 30° of plantar flexion, and the ankle will be passively moved until maximum dorsal flexion that is achieved. Both passive torque and hysteresis will be evaluated at a constant angular velocity of 5°.s
Time frame: The assessment will be performed at the beginning (1-4 days), middle (10-14 days), and end (22-26 days) of Cycle 1 (each menstrual cycle is between 28-30 days).
Passive torque (Nm)
Passive torque will be evaluated with the isokinetic method dynamometer moving the ankle passively for five cycles, from 0° (i.e. 90° angle between foot and leg) to the maximum ROM previously determined for each participant.
Time frame: The assessment will be performed at the beginning (1-4 days), middle (10-14 days), and end (22-26 days) of Cycle 1 (each menstrual cycle is between 28-30 days).
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