Athletes frequently adjust their training volume in line with their athletic competition schedule, onset of sport injury, and retirement. Whether maintenance of partial training activity during the detraining period can preserve optimal body composition and insulin sensitivity is currently unknown. Sixteen elite kayak athletes (mean VO2max: 58.5 ml.kg(-1).min(-1), s = 1.77) were randomly assigned to a totally detrained group (age: 20.8 years, s = 0.7; body mass index: 23.74, s = 0.54) or partially detrained group (age: 21.8 years, s = 0.7; body mass index: 23.20, s = 1.02), whereby totally detrained participants terminated their training routine completely and the partially detrained participants preserved approximately 50% of their previous training duration with equivalent intensity for one month. Body mass, waist circumference, oral glucose tolerance test, insulin, leptin, cortisol, and testosterone were measured during the trained state and after detraining. Waist circumferences for both the partially detrained and totally detrained groups were significantly elevated after detraining, with no group difference. However, body mass was reduced in both groups. Significant elevations in the area under the curve for insulin and fasted leptin with detraining were observed. These changes were greater in the totally detrained participants. In conclusion, the present results show that maintaining partial training activity cannot prevent an increase in waist circumference. During the detraining period, the magnitude of increase in plasma insulin and leptin concentrations was regulated in an activity-dependent manner.
This study established a simultaneous screening method based on solid-phase extraction and liquid chromatography-tandem mass spectrometry (LC-MS-MS) for the detection of 23 stimulants and 23 diuretics in human urine. An electrospray ionization source and multiple reaction monitoring were used for data acquisition. All stimulants and diuretics were separated in less than 12.52 min. The limits of detection were in the range of 25-500 ng/mL for stimulants and 25-125 ng/mL for diuretics. To evaluate the performance of this method, urine samples were collected from 1627 athletes in Taiwan, and 7 positive samples were found. This LC-MS-MS method not only meets the minimum required performance limits set by the World Anti-Doping Agency but also provides a fast way to analyze the authentic urine samples in doping control laboratories.
Background
Water jumping exercise is an alternative method to achieve maintenance of bone health and reduce exercise injuries. Clarifying the ground reaction force (GRF) of moderate and high cardiopulmonary exercise intensities for jumping movements can help quantify the impact force during different exercise intensities. Accelerometers have been explored for measuring skeletal mechanical loading by estimating the GRFs. Predictive regression equations for GRF using ACC on land have already been developed and performed outside laboratory settings, whereas a predictive regression equation for GRF in water exercises is not yet established. The purpose of this study was to determine the best accelerometer wear-position for three exercise intensities and develop and validate the ground reaction force (GRF) prediction equation.
Methods
Twelve healthy women (23.6 ± 1.83 years, 158.2 ± 5.33 cm, 53.1 ± 7.50 kg) were recruited as participants. Triaxial accelerometers were affixed 3 cm above the medial malleolus of the tibia, fifth lumbar vertebra, and seventh cervical vertebra (C7). The countermovement jump (CMJ) cadence started at 80 beats/min and increased by 5 beats per 20 s to reach 50%, 65%, and 80% heart rate reserves, and then participants jumped five more times. One-way repeated analysis of variance was used to determine acceleration differences among wear-positions and exercise intensities. Pearson’s correlation was used to determine the correlation between the acceleration and GRF per body weight on land (GRFVLBW). Backward regression analysis was used to generate GRFVLBW prediction equations from full models with C7 acceleration (C7 ACC), age, percentage of water deep divided by body height (PWDH), and bodyweight as predictors. Paired t-test was used to determine GRFVLBW differences between values from the prediction equation and force plate measurement during validation. Lin’s CCC and Bland–Altman plots were used to determine the agreement between the predicted and force plate-measured GRFVLBW.
Results
The raw full profile data for the resultant acceleration showed that the acceleration curve of C7 was similar to that of GRFv. The predicted formula was − 1.712 + 0.658 * C7ACC + 0.016 * PWDH + 0.008 * age + 0.003*weight. Lin’s CCC score was 0.7453, with bias of 0.369%.
Conclusion
The resultant acceleration measured at C7 was identified as the valid estimated GRFVLBW during CMJ in water.
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