The effect of stride frequencies on running performance at the velocity of VO2max

Running economy(RE) is considered to be a critical factor to improve running performance. Stride frequency(SF) is an important variable for determining RE. The importance of SF has gained more attention in recent years, especially for recreational runners. However, no previous research has investigated the interaction between running performance and SF at the velocity of VO2max. PURPOSE: To investigate the effect of five different SF variations on running performance until volitional fatigue at the velocity of VO2max. METHODS: Fourteen male recreational runners (Age = 25.8 ± 4.96 years, Height = 171 ± 6.2cm, Body Mass = 71.9 ± 7.5kg) measured VO2max (54 ± 5.6 ml/kg/min) and preferred stride frequency (PSF; 89.3 ± 4 / min) through a graded exercise test (GXT) and running session, respectively. Running speed was determined based on each individual’s VO2max via the metabolic equation for gross VO2 in metric units by ACSM. Participants ran on the treadmill (0% grade) with five SF conditions (PSF, ±5%, ±10%) until time to exhaustion. Data were analyzed using a one way ANOVA with repeated measures and Tukey HSD post hoc. RESULTS: The total running performance (time, distance), energy expenditures (kcal), and oxygen consumption (VO2) were statistically significant among SF variations (pE) were no statistically significant (p\u3e0.05). CONCLUSION: The SF variations have a significant influence on running performance. The relationship between SF variations and other variables (RER, RR, VE) were possibly related to the central governor theory to delay the onset of fatigue. These results suggest that recreational runners could use a 105% of PSF to improve running performance with the better RE

Investigation of Swimming Physiology and Swimming Kinematics while Wearing Different Triathlon Wetsuit Styles at Submaximal Front Crawl Swimming in Recreational Population

Triathlon wetsuits are commonly used due to the potential benefits in swimming performance and thermoregulation. Triathletes may select different wetsuit styles depending on many factors such as temperature regulation, swimming technique, body type, and training purpose. However, there is a lack of empirical evidence for how different wetsuit styles affect physiological responses and swimming kinematics during submaximal swimming intensity. Therefore, this studyaimed to investigate the physiological responses and swimming kinematics during submaximal intensity front crawl swimming while wearing different wetsuit styles. Fourteen participants (n=6 male, n=8 female; all recreational triathletes or swimmers) completed a swimming graded exercise test (GXT) wearing only a swimsuit to determine maximal oxygen consumption (V̇O2max). The test swimming pace for the experimental sessions was calculated as 80% of V̇ O2max from the GXT. Participants then completed four wetsuit conditions: regular swimsuit (NWS), buoyancy short (BS), sleeveless (SLW), and full sleeve wetsuit (FSW). Each swim was 4-minutes submaximal at the same test swimming pace. The order of the wetsuit conditions was randomized. All conditions were conducted in a swimming flume and metabolic measurements were made using a metabolic cart with a mixing chamber. The rate of oxygen consumption (V̇O2; ml·kg-1·min-1), rate of carbon dioxide production (V̇CO2; L·min-1), ventilation (VE; L·min-1), heart rate (HR; bpm), respiratory exchange ratio (RER), and cost of transport (COT; J·kg-1·m-1) were determined as the average for the last minute of each condition. The rating of perceived exertion (RPE) was assessed after each condition. Also, the time to completion of 10 strokes was measured for further general stroke characteristics analysis such as stroke rate (SR; Hz), stroke length (SL; m), and stroke index (SI; m2/s). V̇O2, V̇CO2, VE, HR, and COT were each significantly different in the main effect by wetsuit conditions (p \u3c 0.001). RER and RPE were significantly influenced by wetsuit conditions (p \u3c 0.05). Based on the pairwise comparison, swimming without a wetsuit was significantly higher in V̇ O2, V̇ CO2, VE, HR, and RPE relative to the other wetsuit conditions (p \u3c 0.05). Furthermore, V̇O2, V̇CO2, and COT during swimming with buoyancy shorts were significantly higher than SLW and FSW (p \u3c 0.05). However, all dependent variables were not statistically different between SLW and FSW (p \u3e 0.05). Stroke kinematics were not significantly different across the wetsuit conditions (p \u3e 0.05). Positive correlations existed between V̇O2 and HR vs. stroke kinematics (i.e., SR, SL, SI). In addition, there were positive correlations between COT and SR. However, negative correlations existed between COT vs. SL and COT vs. SI. In conclusion, swimming with a regular swimsuit is the least economical at the test pace. In addition, it seems that either SLW or FSW can be used without significant physiological changes when swimming at 80% of V̇ O2max. Stroke kinematics did not change between wetsuit conditions. In addition, improving stroke length and index may be a good strategy for improving swimming efficiency

Shoulder Muscle Activity While Swimming in Different Wetsuits and Across Different Paces

International Journal of Exercise Science 16(1): 172-181, 2023. A triathlon wetsuit is an important piece of equipment during the swim portion of the triathlon for the benefits of thermoregulation and additional buoyancy. However, a lack of knowledge exists about whether or not shoulder muscle activity is influenced by wearing a wetsuit. The purpose of this study was to determine if there were changes in shoulder muscle activity during front crawl with four different wetsuit conditions: Full sleeve (FSW), Sleeveless (SLW), Buoyancy shorts (BS), No wetsuit (NWS) in three different subjective swimming paces (slow, medium, and fast). Eight subjects (5 males, 3 females: mean ± SD, age = 39.1 ± 12.5 years; height = 1.8 ± 0.1 m; mass = 74.6 ± 12.9 kg; percent body fat = 19.0 ± 7.8%) completed twelve total swim conditions (4 wetsuits x 3 swimming pace) in a 25-m indoor pool. Muscle activity in anterior deltoid (AD) and posterior deltoid (PD) were measured using a wireless waterproofed electromyography (EMG) system. Stroke rate (SR) was calculated using the time to complete five-stroke cycles. The AD, PD EMG, and SR were compared using ANOVA with repeated measures. None of the dependent variables showed the interaction between wetsuit conditions and swimming paces (p \u3e 0.05). Both AD and PD muscle activity as well as SR were influenced by swimming pace (p \u3c 0.05) but not wetsuit conditions (p \u3e 0.05). In conclusion, shoulder muscle activity and SR were not influenced by types of wetsuits but influenced by swimming pace

Gate-Tunable Reversible Rashba−Edelstein Effect in a Few-Layer Graphene/2H-TaS2 Heterostructure at Room Temperature

We report the observation of current-induced spin polarization, the Rashba−Edelstein effect (REE), and its Onsager reciprocal phenomenon, the spin galvanic effect (SGE), in a few-layer graphene/2H-TaS2 heterostructure at room temperature. Spin-sensitive electrical measurements unveil full spin-polarization reversal by an applied gate voltage. The observed gate-tunable charge-to-spin conversion is explained by the ideal work function mismatch between 2H-TaS2 and graphene, which allows for a strong interface-induced Bychkov−Rashba interaction with a spin-gap reaching 70 meV, while keeping the Dirac nature of the spectrum intact across electron and hole sectors. The reversible electrical generation and control of the nonequilibrium spin polarization vector, not previously observed in a nonmagnetic material, are elegant manifestations of emergent two-dimensional Dirac Fermions with robust spin-helical structure. Our experimental findings, supported by first-principles relativistic electronic structure and transport calculations, demonstrate a route to design low-power spin−logic circuits from layered materials

Second-Line Irinotecan, Leucovorin, and 5-Fluorouracil for Gastric Cancer Patients after Failed Docetaxel and S-1

Background. This retrospective study aimed to assess the efficacy and toxicities of second-line chemotherapy with irinotecan, leucovorin, and 5-fluorouracil (5-FU) in metastatic gastric cancer (MGC) patients previously treated with docetaxel and S-1 with or without oxaliplatin (DS/DOS). Patients and Methods. We reviewed the data of patients who had previously been treated with first-line DS/DOS and received biweekly irinotecan-based chemotherapy (FOLFIRI/IFL) between October 2004 and November 2011. Results. A total of 209 cycles were administered to 35 patients, with a median of 4 (range, 1–22) cycles each. The overall response rate in 29 response-assessable patients was 17.2%, including 2 complete and 3 partial responses. The median progression-free and overall survivals were 3.81 (95% confidence interval [CI], 1.82–5.80) months and 6.24 (95% CI, 1.44–11.04) months, respectively. The major grade 3/4 toxicity was neutropenia (8.6%). Conclusion. FOLFIRI/IFL chemotherapy showed modest antitumour activity and tolerable toxicities in DS/DOS-treated MGC patients

Second-Line Irinotecan, Leucovorin, and 5-Fluorouracil for Gastric Cancer Patients after Failed Docetaxel and S-1

Background. This retrospective study aimed to assess the efficacy and toxicities of second-line chemotherapy with irinotecan, leucovorin, and 5-fluorouracil (5-FU) in metastatic gastric cancer (MGC) patients previously treated with docetaxel and S-1 with or without oxaliplatin (DS/DOS). Patients and Methods. We reviewed the data of patients who had previously been treated with firstline DS/DOS and received biweekly irinotecan-based chemotherapy (FOLFIRI/IFL) between October 2004 and November 2011. Results. A total of 209 cycles were administered to 35 patients, with a median of 4 (range, 1-22) cycles each. The overall response rate in 29 response-assessable patients was 17.2%, including 2 complete and 3 partial responses. The median progression-free and overall survivals were 3.81 (95% confidence interval [CI], 1.82-5.80) months and 6.24 (95% CI, 1.44-11.04) months, respectively. The major grade 3/4 toxicity was neutropenia (8.6%). Conclusion. FOLFIRI/IFL chemotherapy showed modest antitumour activity and tolerable toxicities in DS/DOS-treated MGC patients