Search results for "cycle"
showing 10 items of 3119 documents
Conditioning hops increase triceps surae muscle force and Achilles tendon strain energy in the stretch-shortening cycle
2018
Postactivation potentiation can improve athletic performance, but the underlying mechanisms are poorly understood. This study investigated the effect of conditioning hops on triceps surae muscle force and tendon strain and its contribution to potentiated stretch-shortening cycle (SSC) performance. Thirty-two subjects participated in two experiments. In both experiments, subjects performed three drop jumps (DJs) after prior conditioning with 10 maximal hops, three unconditioned DJs served as control. Ground reaction forces, kinematics, and triceps surae electromyographic activity were recorded. Ultrasound imaging was used to determine fascicle lengths (FASC) of the gastrocnemius (GM) and sol…
Postactivation potentiation can counteract declines in force and power that occur after stretching.
2016
Stretching can decrease a muscle's maximal force, whereas short but intense muscle contractions can increase it. We hypothesized that when combined, postactivation potentiation induced by reactive jumps would counteract stretch-induced decrements in drop jump (DJ) performance. Moreover, we measured changes in muscle twitch forces and ankle joint stiffness (KAnkle ) to examine underlying mechanisms. Twenty subjects completed three DJs and 10 electrically evoked muscle twitches of the triceps surae subsequent to four different conditioning activities and control. The conditioning activities were 10 hops, 20s of static stretching of the triceps surae muscle, 20s of stretching followed by 10 ho…
Changes in biomechanics of skiing at maximal velocity caused by simulated 20 km skiing race using V2 skating technique
2017
This study investigated how the fatigue caused by a 20 km simulated skating cross-country skiing race on snow affects the final spurt performance from a biomechanical perspective. Subjects performed a 100 meter maximal skiing trial before and at the end of the simulated race. Cycle characteristics, ground reaction forces from skis and poles, and muscle activity from eight muscles were recorded during each trial. Results showed that subjects were in a fatigued state after the simulated race manifested by 11.6% lower skiing speed (P < 0.01). The lower skiing speed was related to an 8.0% decrease in cycle rate (P < 0.01) whereas cycle length was slightly decreased (tendency). In temporal patte…
Ovarian stimulation does not influence the uterine immune environment in healthy infertile women.
2019
Abstract Research question There is some controversy regarding the impact of ovarian stimulation on immune cells in women undergoing IVF. The study's aim was to determine whether ovarian stimulation affected immune uterine cells in healthy women undergoing IVF. Design This prospective cohort study included 28 patients undergoing IVF and 47 healthy oocyte donors. Endometrial biopsies were taken in a natural cycle and after ovarian stimulation. All participants had a normal karyotype, pelvic ultrasound and cervical cytology results and thyroid-stimulating hormone concentration, as well as normal glucose and insulin concentrations and inherited and acquired thrombophilia test results. Screenin…
Influence of sociocultural factors on the ovulatory status of polycystic ovary syndrome.
2009
OBJECTIVE: To evaluate the role of social and cultural differences inside the same ethnic group on the ovulatory status of women with polycystic ovary syndrome (PCOS). DESIGN: To correlate social and cultural status with the phenotypic expression (body weight and ovulation) and with androgen and insulin levels of PCOS. SETTING: University department of medicine. PATIENT(S): Two hundred and forty-four consecutive PCOS women. INTERVENTION(S): All studied patients completed a simple questionnaire to indicate their mean family income and their school education. MAIN OUTCOME MEASURE(S): Ovulation was assessed by measurement of serum progesterone on day 22 of a spontaneous or induced menstrual cy…
Does metformin induce ovulation in normoandrogenic anovulatory women?
2004
Objective: This study was undertaken to evaluate the efficacy of metformin in women with anovulation who do not have evidence for hyperandrogenism and classic polycystic ovary syndrome. Study design: A randomized trial of metformin (1500 mg daily) and placebo in 24 anovulatory women was undertaken for 3 months. Assessments of changes in hormone levels and insulin sensitivity were carried out. Abnormal ormonal values were defined by levels exceeding the range in normal ovulatory controls. Results: Anovulatory women had normal androgen levels and luteinizing hormone but had higher serum insulin and lower insulin sensitivity compared with controls. Over 3 months, there were 16 ovulatory cycles…
Intensity- and muscle-specific fascicle behavior during human drop jumps.
2006
The present study was designed to examine fascicle-tendon interaction in the synergistic medial gastrocnemius (MG) and soleus (Sol) muscles during drop jumps (DJ) performed from different drop heights (DH). Eight subjects performed unilateral DJ with maximal rebounds on a sledge apparatus from different DH. During the exercises, fascicle lengths (using ultrasonography) and electromyographic activities were recorded. The results showed that the fascicles of the MG and Sol muscles behaved differently during the contact phase, but the whole muscle-tendon unit and its tendinous tissue lengthened before shortening in both muscles. The Sol fascicles also lengthened before shortening during the g…
Exhaled nitric oxide is associated with cyclic changes in sexual hormones
2013
Abstract Background We hypothesized that changes in the levels of sexual hormones during the menstrual cycle influence the concentration of nitric oxide in the exhaled air (FeNO) and alveolar exhaled nitric oxide (CANO). Methods Twelve healthy, non allergic women in their reproductive age (age range 25–37 years) were recruited. Subjects were studied, on alternate days, over the course of their menstrual cycle. At each visit, measurements of FeNO and CANO were performed. Progesterone and 17-β-estradiol concentrations were measured in salivary samples. Results Eight subjects completed the study. The levels of FeNO and CANO were 13 ± 4.7 pbb and 3.5 ± 1.9 pbb, respectively (mean ± SD). The mea…
A minimal limit-cycle model to profile movement patterns of individuals during agility drill performance: Effects of skill level.
2015
Identification of control strategies during agility performance is significant in understanding movement behavior. This study aimed at providing a fundamental mathematical model for describing the motion of participants during an agility drill and to determine whether skill level constrained model components. Motion patterns of two groups of skilled and unskilled participants (n = 8 in each) during performance of a forward/backward agility drill modeled as limit-cycles. Participant movements were recorded by motion capture of a reflective marker attached to the sacrum of each individual. Graphical and regression analyses of movement kinematics in Hooke’s plane, phase plane and velocity prof…
Changes in colour discrimination during the menstrual cycle.
2006
A group of normal women of reproductive age were recruited to investigate colour discrimination during the various phases of the menstrual cycle. Colour vision was tested with the Farnsworth-Munsell 100-hue arrangement test, and the test was administered at 3 time points: the beginning of the cycle, ovulation, and the end of the cycle. We found that colour discrimination was better at ovulation than at the other 2 time points. It is possible that psychological as well as hormonal factors could contribute to improved colour vision performance at ovulation.