Caffeine Improves Simulated 800-m Run Performance without Affecting Severe Exercise-Induced Arterial Hypoxemia.

PURPOSE: Although caffeine is known to possess ergogenic effects, previous studies demonstrated no effect of caffeine on 800-m run performance outdoors, which might be due to several uncontrolled factors including pacing strategies. We hypothesized that caffeine ingestion improves a pace-controlled simulated 800-m run performance. We also hypothesized that exercise-induced arterial hypoxemia occurs during the simulated 800-m run, and this response is mitigated by caffeine-induced increases in exercise ventilation. METHODS: In a randomized, double-blind, placebo-controlled and crossover design, 16 (3 females) college middle-distance runners who have 800-m seasonal best of 119.97 ± 7.64 s ingested either 1) placebo (6 mg of glucose per kilogram of body weight) or caffeine (6 mg of caffeine per kilogram of body weight). Then they performed an 800-m run consisting of 30-s running at 103% of their 800-m seasonal best, followed by running at 98% of seasonal best until exhaustion, which mimics actual 800-m run pacing pattern. RESULTS: Running time to exhaustion was extended by 7.3% ± 6.2% in the caffeine-ingested relative to placebo trial (123 ± 12 vs 114 ± 9 s, P = 0.04). Arterial oxygen saturation markedly decreased during the simulating running, but this response was similar (76.6% ± 5.7% vs 81.1% ± 5.2%, at 113 s of the simulating running) between the caffeine and placebo trials ( P ≥ 0.23 for time-supplement interaction and main effect of supplement). Minute ventilation, oxygen uptake (all P ≥ 0.36 for time-supplement interaction and main effect of supplement), and rate of perceived exertion (all P ≥ 0.11) did not differ between the trials throughout the simulating running. Heart rate was higher in the caffeine-ingested trial throughout the simulated running ( P < 0.01 for main effect of supplement). Postexercise blood lactate concentration was higher in the caffeine trial ( P = 0.02). CONCLUSIONS: Caffeine ingestion improves simulated 800-m run performance without affecting exercise ventilation and severe exercise-induced arterial hypoxemia.

Estimation of Foot Trajectory and Stride Length during Level Ground Running Using Foot-Mounted Inertial Measurement Units.

Zero-velocity assumption has been used for estimation of foot trajectory and stride length during running from the data of foot-mounted inertial measurement units (IMUs). Although the assumption provides a reasonable initialization for foot trajectory and stride length estimation, the other source of errors related to the IMU's orientation still remains. The purpose of this study was to develop an improved foot trajectory and stride length estimation method for the level ground running based on the displacement of the foot. Seventy-nine runners performed running trials at 5 different paces and their running motions were captured using a motion capture system. The accelerations and angular velocities of left and right feet were measured with two IMUs mounted on the dorsum of each foot. In this study, foot trajectory and stride length were estimated using zero-velocity assumption with IMU data, and the orientation of IMU was estimated to calculate the mediolateral and vertical distance of the foot between two consecutive midstance events. Calculated foot trajectory and stride length were compared with motion capture data. The results show that the method used in this study can provide accurate estimation of foot trajectory and stride length for level ground running across a range of running speeds.

CO2-Enriched Air Inhalation Modulates the Ventilatory and Metabolic Responses of Endurance Runners During Incremental Running in Hypobaric Hypoxia.

Cao, Yinhang, Naoto Fujii, Tomomi Fujimoto, Yin-Feng Lai, Takeshi Ogawa, Tsutomu Hiroyama, Yasushi Enomoto, and Takeshi Nishiyasu. CO2-enriched air inhalation modulates the ventilatory and metabolic responses of endurance runners during incremental running in hypobaric hypoxia. High Alt Med Biol. 23:125-134, 2022. Aim: We measured the effects of breathing CO2-enriched air on ventilatory and metabolic responses during incremental running exercise under moderately hypobairc hypoxic (HH) conditions. Materials and Methods: Ten young male endurance runners [61.4 ± 6.0 ml/(min·kg)] performed incremental running tests under three conditions: (1) normobaric normoxia (NN), (2) HH (2,500 m), and (3) HH with 5% CO2 inhalation (HH+CO2). The test under NN was always performed first, and then, the two remaining tests were completed in random and counterbalanced order. Results: End-tidal CO2 partial pressure (55 ± 3 vs. 35 ± 1 mmHg), peak ventilation (163 ± 14 vs. 152 ± 12 l/min), and peak oxygen uptake [52.3 ± 5.5 vs. 50.5 ± 4.9 ml/(min·kg)] were all higher in the HH+CO2 than HH trial (all p < 0.01), respectively. However, the duration of the incremental test did not differ between HH+CO2 and HH trials. Conclusion: These data suggest that chemoreflex activation by breathing CO2-enriched air stimulates breathing and aerobic metabolism during maximal intensity exercise without affecting exercise performance in male endurance runners under a moderately hypobaric hypoxic environment.

Food Quotient Assessments Using One-Week Dietary Records and Food Frequency Questionnaires of Young Japanese Runners.

The food quotient (FQ), which is the rate of macronutrient composition calculated from daily meals, can equal the respiratory quotient over a long term. The FQ is needed to estimate the total energy expenditure (TEE) in doubly labeled water studies. Usually, dietary records (DR) are used for dietary assessment in clinical nutritional studies; however, the DR method's disadvantage is that it takes time to calculate the results. In comparison, the food frequency questionnaires (FFQ) method is a simple and quick way to calculate results. This study aimed to assess the FQ in Japanese runners, and to compare the two dietary assessment methods, DR and FFQ, to examine whether FFQ is useful in calculating the FQ in healthy young adults and runner. The study consisted of 27 runners and 22 healthy young adults. The participants recorded and took pictures all their meals for 1 wk and provided the FFQ for the same week. The FQ was calculated using the proportions of proteins, fats, carbohydrates, and alcohol. There were no significant differences between the FQs of the runners 0.867 (male: 0.873, female: 0.863) and the healthy young adults 0.871 (male: 0.875, female: 0.867) according to the DR methods. There were no differences in the FQs between DR and FFQ methods for all groups. A significant correlation between the FQs (r=0.502, p<0.01), estimated using the DR, and the FQs estimated using the FFQ was observed. These results suggest that use of the FFQ method can provide comparable data for runners and healthy young adults.

Enhancing the Sensitivity of Lateral Flow Immunoassay by Magnetic Enrichment Using Multifunctional Nanocomposite Probes.

For lateral flow immunoassay (LFIA), it is an important challenge to enhance the detection sensitivity to the same level as polymerase chain reaction or enzyme-linked immunosorbent assay to make LFIA pervasive in the field of on-site environmental analysis. We recently demonstrated that the LFIA sensitivity is dramatically enhanced by using Pt-nanoparticle-latex nanocomposite beads (Pt-P2VPs) as probes for the detection of the influenza A (H1N1) antigen compared with using conventional Au colloids as probes. Here, to further enhance the LFIA sensitivity using Pt-P2VPs, superparamagnetic iron oxide nanoparticles (SPIONs) were chemically conjugated to Pt-P2VPs (Pt-P2VP@SPION) to give them magnetic separation capability (enrichment and/or purification). To investigate the effect of magnetic enrichment on the LFIA sensitivity in a sandwich format, the C-reactive protein (CRP) was chosen as a model analyte and anti-CRP antibody (CRPAb)-conjugated Pt-P2VP@SPION (Pt-P2VP@SPION-CRPAb) beads were used as probes. The visual limit of detection (LOD) of LFIA was successfully lowered by increasing the magnetic enrichment factor φ. The minimum LOD under the present experimental conditions was 0.08 ng/mL for φ = 40, which is 26-fold lower than that of the standard Au-nanoparticle-based LFIA. In theory, the LOD can be unlimitedly decreased by just increasing φ. However, the times required for both the antigen-antibody binding reaction and magnetic separation dramatically increase with φ. We also propose solutions to overcome this drawback.

Naked-eye detection of specific DNA sequences amplified by the polymerase chain reaction with nanocomposite beads.

We developed a novel nanocomposite bead system for detection by the naked eye of specific DNA sequences amplified by the polymerase chain reaction (PCR). The DNA probes, which were complementary to the target DNA, are conjugated with the nanocomposite beads. If the amplified products contained sequences complementary to the probes, the beads aggregated through sandwich hybridization. The aggregation was detectable as precipitation of the nanocomposite beads. The results were determined visually and did not require instrumental detection. The assay was sensitive enough to detect PCR products with a detection limit of 10 copies/tube for DNA templates. This technique is that all needed components are included within the initial cap, so that the risk of carryover contamination is very low. The nanocomposite bead system has broad application prospects for the detection of specific DNA sequences in biological and biomedical research.

Biomechanical factors affecting energy cost during running utilising different slopes.

This study aimed to examine the characteristics of electromyography (EMG) and kinematics of the supporting leg affecting energy cost while running at incline, level, and decline slopes. Twelve male Japanese middle- and long-distance runners volunteered for this study. The subjects were asked to run at 13.5 km·h-1 on a treadmill under three slope conditions. Sagittal plane kinematics and the EMG of the lower limb muscles, respiratory gases were recorded. Energy cost differed significantly between slopes, being the lowest in decline slope and the greatest in incline slope. Integrated EMG (iEMG) of leg extensor muscles was greater in the incline slope than in the decline slope, and iEMG of the gastrocnemius and soleus muscles correlated positively with energy cost. The knee and ankle joint kinematics were associated with energy cost during running. In incline slope, the knee and ankle joints were more extended (plantarflexed) to lift the body. These movements may disturb the coordination between the ankle and knee joints. The gastrocnemius muscle would do greater mechanical work to plantarflex the ankle joint rather than transfer mechanical energy as well as greater mechanical work of mono-articular muscles. These muscular activities would increase energy cost.

Expiratory flow limitation under moderate hypobaric hypoxia does not influence ventilatory responses during incremental running in endurance runners.

We tested whether expiratory flow limitation (EFL) occurs in endurance athletes in a moderately hypobaric hypoxic environment equivalent to 2500 m above sea level and, if so, whether EFL inhibits peak ventilation ( V˙ Epeak ), thereby exacerbating the hypoxia-induced reduction in peak oxygen uptake ( V˙ O2peak ). Seventeen young male endurance runners performed incremental exhaustive running on separate days under hypobaric hypoxic (560 mmHg) and normobaric normoxic (760 mmHg) conditions. Oxygen uptake ( V˙ O2 ), minute ventilation ( V˙ E), arterial O2 saturation (SpO2 ), and operating lung volume were measured throughout the incremental exercise. Among the runners tested, 35% exhibited EFL (EFL group, n = 6) in the hypobaric hypoxic condition, whereas the rest did not (Non-EFL group, n = 11). There were no differences between the EFL and Non-EFL groups for V˙ Epeak and V˙ O2peak under either condition. Percent changes in V˙ Epeak (4 ± 4 vs. 2 ± 4%) and V˙ O2peak (-18 ± 6 vs. -16 ± 6%) from normobaric normoxia to hypobaric hypoxia also did not differ between the EFL and Non-EFL groups (all P > 0.05). No differences in maximal running velocity, SpO2 , or operating lung volume were detected between the two groups under either condition. These results suggest that under the moderate hypobaric hypoxia (2500 m above sea level) frequently used for high-attitude training, ~35% of endurance athletes may exhibit EFL, but their ventilatory and metabolic responses during maximal exercise are similar to those who do not exhibit EFL.

Anticancer effect of novel platinum nanocomposite beads on oral squamous cell carcinoma cells.

Nanoparticles are used in industry and medicine, because of their physiochemical properties, such as size, charge, large surface area and surface reactivity. Recently, metal nanoparticles were reported to show cell toxicity on cancer cells. In this study, we focused novel platinum nanoparticles-conjugated latex beads (P2VPs), platinum nanocomposite (PtNCP) beads, and investigated the possibility to incorporate novel anti-cancer effect of these combined nanoparticles. Oral squamous cell carcinoma cell lines, HSC-3-M3 cells were injected subcutaneously into the back of nude mice to produce a xenograft model. PtNCP beads were injected locally and examined by measuring tumor volume and comparing pathological histology. PtNCP beads treatment suppressed tumor growth and identified increasing pathological necrotic areas, in vivo. PtNCP beads inhibited the cell viability of HSC-3-M3 cells in dose-dependent manner and induced the cytotoxicity with extracellular LDH value, in vitro. Furthermore, SEM images were morphologically observed in PtNCP beads-treated HSC-3-M3 cells. The aggregation of the PtNCP beads on the cell membrane, the destructions of the cell membrane and globular structures were observed in the SEM image. Our results indicated that a potential anti-cancer effect of the PtNCP beads, suggesting the possibility as a therapeutic tool for cancer cell-targeted therapy. © 2019 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater 107B: 2281-2287, 2019.

Effects of Joint Kinetics on Energy Cost during Repeated Vertical Jumping.

PURPOSE: The present study was designed to investigate the effects of lower limb joint kinetics on energy cost during jumping. METHODS: Eight male middle and long-distance runners volunteered for the study. The subjects were asked to repeat vertical jumps at a frequency of 2 Hz for 3 min on a force platform in three different surface inclination conditions: Incline (+8°), Level (0°), and Decline (-8°). Sagittal plane kinematics were obtained using a high-speed video camera. Simultaneously, ground reaction forces and EMG of the lower limb muscles were recorded. Energy cost was calculated using steady-state oxygen uptake, respiratory ratio, and vertical distance of the body. RESULTS: In all conditions, energy cost correlated positively with total mechanical work of the knee joint (r = 0.636, P < 0.01), but negatively with total mechanical work of the ankle joint (r = -0.584, P < 0.01). The muscle-tendon complex length of the gastrocnemius and soleus muscles were significantly longer in incline than in level and decline. The gastrocnemius muscle showed different activity pattern in decline as compared with the incline and level conditions. CONCLUSIONS: The present study revealed that the ankle and knee joint kinematics and, therefore muscles' coordination are associated with energy cost during repeated vertical jumping. The lower limb joints contributed different efficiencies to generate the same total mechanical work in repeated vertical jumping on different surface inclinations. Energy cost was smaller when mechanical work was mainly done by ankle joint. Whereas, when the ankle joint did less mechanical work, the knee and/or hip joints compensated for the lack of mechanical work of the ankle joint and energy cost was increased.

Effects of work-matched supramaximal intermittent vs. submaximal constant-workload warm-up on all-out effort power output at the end of 2 minutes of maximal cycling.

We tested the hypothesis that work-matched supramaximal intermittent warm-up improves final-sprint power output to a greater degree than submaximal constant-intensity warm-up during the last 30 s of a 120-s supramaximal exercise simulating the final sprint during sports events lasting approximately 2 min. Ten male middle-distance runners performed a 120-s supramaximal cycling exercise consisting of 90 s of constant-workload cycling at a workload corresponding to 110% maximal oxygen uptake (VO2max) followed by 30 s of maximal-effort cycling. This exercise was preceded by 1) no warm-up (Control), 2) a constant-workload cycling warm-up at a workload of 60%VO2max for 6 min and 40 s, or 3) a supramaximal intermittent cycling warm-up for 6 min and 40 s consisting of 5 sets of 65 s of cycling at a workload of 46%VO2max + 15 s of supramaximal cycling at a workload of 120%VO2max. By design, total work was matched between the two warm-up conditions. Supramaximal intermittent and submaximal constant-workload warm-ups similarly increased 5-s peak (590 ± 191 vs. 604 ± 215W, P = 0.41) and 30-s mean (495 ± 137 vs. 503 ± 154W, P = 0.48) power output during the final 30-s maximal-effort cycling as compared to the no warm-up condition (5-s peak: 471 ± 165W; 30-s mean: 398 ± 117W). VO2 during the 120-s supramaximal cycling was similarly increased by the two warm-ups as compared to no-warm up (P ≤ 0.05). These findings show that work-matched supramaximal intermittent and submaximal constant-workload warm-ups improve final sprint (∼30 s) performance to similar extents during the late stage of a 120-s supramaximal exercise bout.

Metal (Au, Pt) Nanoparticle-Latex Nanocomposites as Probes for Immunochromatographic Test Strips with Enhanced Sensitivity.

The development of a sensitive and rapid diagnostic test for early detection of infectious viruses is urgently required to defend against pandemic and infectious diseases including seasonal influenza. In this study, we developed noble metal (Au, Pt) nanoparticle-latex nanocomposite particles for use as probes for immunochromatographic test (ICT) strips. The nanocomposite particles were conjugated with monoclonal antibody (mAb) to detect an influenza A (H1N1) antigen. For comparison, Au nanoparticles conjugated with mAb were also prepared. The lowest detectable concentrations of the influenza A antigen were found to be 6.25 × 10-3 and 2.5 × 10-2 HAU/mL for Au nanoparticle-latex and Pt nanoparticle-latex nanocomposite particles, respectively, whereas it was 4.0 × 10-1 HAU/mL for Au nanoparticles. These results clearly demonstrated that the nanocomposite probes were more sensitive than conventional nanoparticle-based probes for ICT. To expand the versatility of the nanocomposite probes, the surfaces of the probes were functionalized with biotinylated proteins to enable modification of their surfaces with desired biotinylated antibodies through biotin-avidin binding.

Fabrication of copper damascene patterns on polyimide using direct metallization on trench templates generated by imprint lithography.

Facile imprint and wet chemical processes were used to fabricate copper damascene patterns on polyimide substrate. Poly(amic acid) substrate with trench structures as template has been successfully prepared by imprint lithography using a poly(dimethylsiloxane) mold. The doped Ni(2+) ions into a template through ion-exchange reaction were reduced by an aqueous NaBH(4) solution, resulting in the formation of a nickel thin layer along the surface structure of the template. The resulting nickel films can act as catalyst for subsequent electrodeposition of copper. After electrodeposition, a polishing process was carried out for removing excess deposited copper films, followed by imidization of the substrate. The resulting damascene structured copper films exhibited fine and good adhesion with the polyimide substrate, and they could be utilized for good application in the fields of minute copper circuit patterns on insulating substrates.

Joint torque and mechanical energy flow in the support legs of skilled race walkers.

This study analyzed the joint torque and the mechanical energy flow in the support legs of skilled male race walkers. Twelve race walkers were videotaped using a high-speed camera at a frame rate of 250 Hz set perpendicular to the sagittal plane of motion; their ground reaction forces were measured with two force platforms. A two-dimensional, 14-segment, linked model was used to calculate the kinetics of the support leg joints. In the initial part of the support phase, the mechanical energy flowed into the thigh and shank by the torque of the large hip extensors and knee flexors. In the middle part, the mechanical energy generated by the torque of the large plantar flexors flowed to the foot and from the foot to the shank by the ankle joint force. The mechanical energy flow by the forward joint force of the support hip was significantly related to the walking speed in the final part of the support phase. Our findings suggest that race walkers in the final part of the support phase should exert the torque of the knee extensors and hip flexors to transfer the mechanical energy more effectively to the support thigh and shank.

Mechanical energy flow in the recovery leg of elite race walkers.

The purpose of this study was to investigate the mechanical energy flow in the recovery leg and its relationship to performance descriptors of elite male race walkers in an official race. Male race walkers participating in official 20 km races were videotaped with a VTR camera (60 Hz) set perpendicular to the course. The 28 elite race walkers (race records 1:19'50"-1:33'58") were selected as subjects. A two dimensional 14-segment linked model was used to calculate biomechanical parameters from the walking motion in the early phase of the race. The walking speed was significantly related to the step length but not related to the step frequency. Large mechanical energy flows at the hip occurred from the trunk to the foot during the first half of the recovery phase and from the foot to the trunk during the second half by the joint force power. Joint force powers at the hip in the second half of the recovery phase were significantly related to the walking speed and the step length. It is suggested that large joint force power at the hip would be one of the important factors to obtain high walking speed.