Background: The mechanism of aerobic improvement after altitude training (AT) has not been resolved yet. Few studies have looked at microcirculation changes after AT in athletes. Materials and Methods: Thirty-three male rowers were recruited and divided into either the AT (n = 18, altitude 2,280 m) or the sea level training (ST group, n = 15, altitude 50 m) for 8 weeks training. Microcirculation function was monitored using a laser Doppler flowmeter. VO 2peak and ergometer 5 km time trial (Er5k) were conducted. Results: Within the AT group there was an 8.8% increment in VO 2peak from pre-to post-training (4,708.9 -455.2 vs. 5,123.3 -391.2 ml/min, p < 0.01), whereas in ST group there was a 3.1% increase of VO 2peak from pre-to posttraining (4,975.4 -501.1 vs. 5,128.0 -499.3 m/min, p = 0.125). Er5k performance in AT group was significantly improved (1,040.3 -26.3 vs. 1,033.2 -27.5 seconds, p = 0.038), whereas in ST group Er5k performance was not improved (1,059.6 -30.9 vs. 1,060.4 -33.2 seconds, p = 0.819). Postocclusive reactive hyperemia reserve and heat reserve in the forearm of AT subjects increased significantly after 8 weeks. Meanwhile, the AT group's resting blood flow and cutaneous vascular conductance (CVC) of the thigh were higher after AT. For the ST group, resting blood flow and CVC in the thigh decreased significantly at third week post-training. There was a low correlation between the change of VO 2peak and blood flow of the thigh (r = 0.45, p = 0.01). Conclusions: Trained rowers benefit more from 8 weeks of AT than from 8 weeks ST in terms of aerobic capacity. We have found that 8 weeks of AT increases thigh blood flow and improves endothelial function.

The purpose of this study was to investigate the differences in the physical fitness characteristics of Chinese single-handed dinghy and 470 sailors, predict the single-handed dinghy sailors’ physical factors on the performance by equation to guide the training. The sample of this study consisted of one hundred and sixty-seven Chinese sailors who participated in the 2020 China National Sailing Championships, K Independent Samples Test was used to analyze the differences of different classes sailors, and the performance of Laser and Laser Radial sailors were analyzed by step multivariate linear regression. The results showed that the 470 helmsmen are shorter, lighter and have a lower BMI, 470 crew are similar in height to the single-handed dinghy sailors, but lower in weight and BMI. Laser sailors have better strength and flexibility than the ones of male 470. There is no significant difference in the physical fitness characteristics between the Laser Radial sailors and the female 470 crew, they both had better upper and lower body strength than female 470 helmsmen. The regression equation is possible to explain 65.5% of the performance of the sailors in Laser = 90.963-1.33 × sailing experience-0.461 × bench press-0.018 × cycling peak power out; The regression equation is possible to explain 76.7% of the performance of the sailors in Laser Radial = 27.433-0.391 × sailing experience+0.351 × vertical jump-0.329 × pull-up-0.027 × cycling peak power out. Performance in laser and Laser Radial sailors will be determined by the technique and tactics (sailing experience) as well as physical fitness.

Transient receptor potential vanilloid 1 (TRPV1) is a protein that is susceptible to cell environment temperature. High temperatures of 40–45°C can activate the TRPV1 channel. TRPV1 is highly expressed in skeletal muscle and located on the sarcoplasmic reticulum (SR). Therefore, TRPV1 activated by high-temperature stress releases Ca2+ from the SR to the cytoplasm. Cellular Ca2+ accumulation is a key event that enhances TRPV1 activity by directly binding to the N-terminus and C-terminus. Moreover, Ca2+ is the key messenger involved in regulating mitochondrial biogenesis in skeletal muscle. Long-term activation of TRPV1 may promote mitochondrial biogenesis in skeletal muscle through the Ca2+-CaMKII-p38 MAPK-PGC-1α signaling axis. The discovery of the TRPV1 channel highlights the potential mechanism for high-temperature stress improving muscle mitochondrial biogenesis. The appropriate hot stimulus in thermal environments might be beneficial to the muscular mitochondrial adaptation for aerobic capacity. However, the investigation of TRPV1 on mitochondrial biogenesis is at an early stage. Further investigations need to examine the role of TRPV1 in response to mitochondrial biogenesis in skeletal muscle induced by different thermal environments.

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