Wearable near-infrared spectroscopy: reliability and sensitivity among different endurance cycling exercise intensities

The present study investigated the reliability and sensitivity of a wearable near-infrared spectroscopy (wNIRS) device in moderate and heavy exercise intensity domains. On three separate days, eleven males performed an incremental test to exhaustion, and in the following visits, four submaximal constant-load bouts (i.e., test and retest) were performed in the moderate-intensity domain (100 and 130 W) and heavy-intensity domain (160 and 190 W). The local tissue oxygen saturation index (SmO2) and pulmonary oxygen uptake (V̇O2) were measured continuously. The absolute SmO2 and V̇O2 values and the change (Δ) from the 3rd to 6th min of exercise were calculated. There was good reliability for SmO2 measurements, as indicated by the high intraclass correlation coefficient analysis (ICC ≥0.84 for all) and low coefficient of variation between the two trials (CV ≤4.1% for all). Steady-state responses were observed for SmO2 and V̇O2 from the 3rd to the 6th min in the two moderate-intensity bouts (P>0.05), whereas SmO2 decreased and V̇O2 increased from the 3rd to the 6th min in the two heavy-intensity bouts (P<0.05). Together, these findings suggested that the SmO2 measured with a wNIRS device is reliable and sensitive to track local metabolic changes provoked by slight increments in exercise intensity.

Association between age and muscle function, architecture, and composition in long-distance master runners: a cross-sectional study

The aim of this study was to describe the muscle function, architecture, and composition of long-distance master runners, and verify the association between age and these variables. Additionally, different clusters of runners were compared based on age and training variables. Forty male runners (≥50 years) reported their training routine and had their muscle function evaluated through maximum knee extensor isometric peak torque (PT) assessed with an isokinetic dynamometer. The cross-sectional area (CSA), pennation angle (PA), fascicle length (FL), muscle thickness (MT), and echo intensity (EI) were evaluated through ultrasound (muscle architecture and composition). The participants were 58.7±6.2 years old and had been training for 18.4±10.3 years, 4 sessions/week with 298.8±164.7 min/week of training. The absolute torque was 226.92±63.44 N·m, and the specific torque (PT/CSA) was 7.29±3.78 N·m/cm2. Regarding muscle architecture, the phase angle was 17.34±4°, the fascicle angle 6.78±1.04 cm, muscle thickness 2.93±0.56 cm, and the cross-sectional area 21.24±5.88 cm2. Concerning muscle composition, the master runners showed echo intensity values of 62.05±11.68 AU. The analysis demonstrated a weak and negative association between age and some muscle architecture variables (CSA and MT) and muscle function (PT). No association was verified between age and muscle composition (EI). Age partially explained CSA, MT, and muscle function changes (13, 11, and 14%, respectively). Participants' high level of physical training might have contributed to the low association between these variables and the lack of association with muscle composition.

Effects of caffeine on central and peripheral fatigue following closed- and open-loop cycling exercises

We examined whether endurance performance and neuromuscular fatigue would be affected by caffeine ingestion during closed- and open-loop exercises. Nine cyclists performed a closed-loop (4,000-m cycling time trial) and an open-loop exercise (work rate fixed at mean power of the closed-loop trial) 60 min after ingesting caffeine (CAF, 5 mg/kg) or placebo (PLA, cellulose). Central and peripheral fatigue was quantified via pre- to post-exercise decrease in quadriceps voluntary activation and potentiated twitch force, respectively. Test sensitivity for detecting caffeine-induced improvements in exercise performance was calculated as the mean change in time divided by the error of measurement. Caffeine ingestion reduced the time of the closed-loop trial (PLA: 375.1±14.5 s vs CAF: 368.2±14.9 s, P=0.024) and increased exercise tolerance during the open-loop trial (PLA: 418.2±99.5 s vs CAF: 552.5±106.5 s, P=0.001), with similar calculated sensitivity indices (1.5, 90%CI: 0.7-2.9 vs 2.8, 90%CI: 1.9-5.1). The reduction in voluntary activation was more pronounced (P=0.019) in open- (-6.8±8.3%) than in closed-loop exercises (-1.9±4.4%), but there was no difference between open- and closed-loop exercises for the potentiated twitch force reduction (-25.6±12.8 vs -26.6±12.0%, P>0.05). Caffeine had no effect on central and peripheral fatigue development in either mode of exercise. In conclusion, caffeine improved endurance performance in both modes of exercise without influence on post-exercise central and peripheral fatigue, with the open-loop exercise imposing a greater challenge to central fatigue tolerance.

Effect of different pacing strategies on 4-km cycling time trial performance

In cycling, there is a body of evidence that supports that an all-out start strategy is superior to an even-pacing strategy, but it is unknown whether an all-out start strategy is superior to a self-paced strategy. In the present study, we investigated the effects of three different pacing strategies on 4-km cycling time trial performance. After preliminary trials (familiarization trials and a baseline 4-km cycling time trial), in a randomized and counterbalanced order, twelve male cyclists (32.3±7.2 years old, maximum rate of O2 uptake (V̇O2peak) 4.3±0.4 L/min) completed: 1) a self-paced 4-km cycling time trial; 2) an all-out start (∼10 s), followed by maintenance of the average baseline trial power for the first km and self-paced cycling for the remaining trial (all-out+mean); and 3) an all-out start (∼10 s), followed by a power 5% above the average baseline trial power for the first km and self-paced cycling for the remaining trial (all-out+5%mean). Although there was a significant interaction between power and distance (P=0.001) with different power distribution profiles throughout the trial, there was no significant difference (P=0.99) between the three strategies for overall exercise performance (self-paced 379.8±13.9 s, all-out+mean 380.0±16.0 s, and all-out+5%mean 380.2±11.5 s). Oxygen uptake, rating of perceived effort, and heart rate were also similar across the pacing strategies. Different all-out start strategies did not confer additional benefits to performance compared to a self-paced strategy.

Caffeine intake reduces sedentary time and increases physical activity predisposition in obese police officers

Sedentary time is associated with increased obesity in police officers. Caffeine intake may reduce sedentary time but it has not been extensively investigated. In the present study, the effect of caffeine ingestion on sedentary time was investigated in obese police officers. Fourteen obese police officers ingested either 5 mg/kg of caffeine or cellulose (placebo) for six days. Information on inactivity time, time spent with physical activities, self-reported perception of tiredness, and physical activity disposition was obtained daily during the intervention period. Sedentary and physical activity times were divided into two intraday periods (T1: 08:00 am-02:00 pm and T2: 02:00 pm-08:00 pm). Caffeine intake decreased the sedentary time in both T1 (79.2±2.2%) and T2 (79.1±2.5%), when compared with T2 of the placebo condition (81.1±3.6%, P<0.05). Caffeine intake also increased the time spent on light physical activities in T1 and T2 (17±2 and 18±2%), when compared with T2 of the placebo condition (16±3%, P<0.05). In addition, sedentary time increased and light physical activity time decreased from T1 to T2 in the placebo (P<0.001) but not in the caffeine condition (P=0.81). Caffeine intake had no effect on tiredness (P>0.05), but it increased the self-reported physical activity disposition compared to the placebo condition (4.5±2.7 vs 3.2±2.3 units, P<0.05). Caffeine intake reduced the sedentary time and increased the time spent on light physical activities of obese police officers, which seems to be related to a higher disposition for the practice of physical activity.

Caffeine ingestion improves specific artistic swimming tasks

The main movements of artistic swimming demand various physical capacities such as flexibility, strength, power, and muscular endurance. The use of ergogenic resources to potentialize performance in this sport, however, is underexplored and deserves investigation. In the present study, we tested whether caffeine ingestion would improve the execution of movements that are essential in a typical figure competition or routines in artistic swimming (i.e., amplitude in the Ariana, height in the Boost and Barracuda, and time maintained in the Stationary Scull techniques). Sixteen experienced female athlete artistic swimmers (17.4±3.2 years of age, 5.6±2.8 years of artistic swimming practice) performed several movements of artistic swimming after having ingested a capsule containing caffeine (5 mg/kg body mass) or cellulose (placebo). Compared to the placebo, caffeine improved latero-lateral amplitude during the Ariana (P=0.035), the height of the Boost and Barracuda (P=0.028 and 0.009), and maintained duration in Stationary Sculling (P=0.012). Bayes factor analysis, however, indicated substantial evidence of a positive effect of caffeine only on the Barracuda and Stationary Scull techniques. These findings indicated that caffeine improved performance during specific artistic swimming movements. Coaches and athletes should consider caffeine ingestion in their supplementation plans.

Footwear designed to enhance energy return improves running economy compared to a minimalist footwear: does it matter for running performance?

The present study compared the effects of a footwear designed to enhance energy return (thermoplastic polyurethane, TPU) vs minimalist shoes on running economy (RE) and endurance performance. In this counterbalanced and crossover design study, 11 recreational male runners performed two submaximal constant-speed running tests and two 3-km time-trials with the two shoe models. Oxygen uptake was measured during submaximal constant-speed running tests in order to determine the RE at 12 km/h and oxygen cost of running (CTO2) at individual average speed sustained during the 3-km running time-trials wearing either of the two shoes. Our results revealed that RE was improved (2.4%) with TPU shoes compared with minimalist shoes (P=0.01). However, there was no significant difference for CTO2 (P=0.61) and running performance (P=0.52) comparing the TPU (710±60 s) and the minimalist (718±63 s) shoe models. These novel findings demonstrate that shoes with enhanced mechanical energy return (i.e. TPU) produced a lower energy cost of running at low (i.e., 12 km/h) but not at high speeds (i.e., average speed sustained during the 3-km running time-trial, ∼15 km/h), ultimately resulting in similar running performance compared to the minimalist shoe.

Are experienced and high-level race walking athletes able to match pre-programmed with executed pacing?

The objective of this study was to verify the agreement between pre-programmed and executed pacing during race walking and whether level of the athletes experience and performance influenced this relationship. Twenty-nine national and international race walkers participated in this study (14 males, 24.0±7.1 years old, and 15 females, 23.3±7.3 years old). Pre-programmed pacing for 10- and 20-km official walking races was self-selected via demonstrative pacing charts prior to races, while executed pacing was analyzed by a specialist investigator via an individual plot of current velocity versus distance. There was no agreement between pre-programmed and executed pacing (P=0.674). There was no association between the ability to match the pre-programmed pace with the executed pace and race walking experience or level of performance. Low- and high-performance athletes pre-programmed a similar pacing profile (P=0.635); however, high-performance athletes generally executed an even pacing strategy, while low-performance athletes generally adopted a positive pacing strategy (P=0.013). Race walkers did not faithfully match their pre-programmed with their executed pacing, and this seemed to be independent of previous experience and level of performance. High-performance athletes, however, tended to execute an even pacing strategy, even though this had not been pre-programmed.

Does caffeine ingestion before a short-term sprint interval training promote body fat loss?

We investigated the effect of caffeine ingestion combined with a 2-wk sprint interval training (SIT) on training-induced reductions in body adiposity. Twenty physically-active men ingested either 5 mg/kg of cellulose as a placebo (PLA, n=10) or 5 mg/kg of caffeine (CAF, n=10) 60 min before each SIT session (13×30 s sprint/15 s of rest). Body mass and skinfold thickness were measured pre- and post-training. Energy expenditure was measured at rest, during exercise, and 45 min after exercise in the first SIT session. Body fat was similar between PLA and CAF groups at pre-training (P>0.05). However, there was a significant decrease in body fat after training in the CAF group (−5.9±4.2%, P<0.05) but not in PLA (1.5±8.0%, P>0.05). There was no difference in energy expenditure at rest and during exercise between PLA and CAF groups (P>0.05), but the post-exercise energy expenditure was 18.3±21.4% greater in the CAF than in the PLA group (P<0.05). In conclusion, caffeine ingestion before SIT sessions induced a body fat loss that may be associated with higher post-exercise energy expenditure.

Energy system contribution in a maximal incremental test: correlations with pacing and overall performance in a 10-km running trial

This study aimed to verify the association between the contribution of energy systems during an incremental exercise test (IET), pacing, and performance during a 10-km running time trial. Thirteen male recreational runners completed an incremental exercise test on a treadmill to determine the respiratory compensation point (RCP), maximal oxygen uptake (V˙O2max), peak treadmill speed (PTS), and energy systems contribution; and a 10-km running time trial (T10-km) to determine endurance performance. The fractions of the aerobic (WAER) and glycolytic (WGLYCOL) contributions were calculated for each stage based on the oxygen uptake and the oxygen energy equivalents derived by blood lactate accumulation, respectively. Total metabolic demand (WTOTAL) was the sum of these two energy systems. Endurance performance during the T10-km was moderately correlated with RCP, V˙O2maxand PTS (P<@0.05), and moderate-to-highly correlated with WAER, WGLYCOL, and WTOTAL (P<0.05). In addition, WAER, WGLYCOL, and WTOTAL were also significantly correlated with running speed in the middle (P<0.01) and final (P<0.01) sections of the T10-km. These findings suggest that the assessment of energy contribution during IET is potentially useful as an alternative variable in the evaluation of endurance runners, especially because of its relationship with specific parts of a long-distance race.

Association between anaerobic components of the maximal accumulated oxygen deficit and 30-second Wingate test

The purpose of this study was to analyze the relationship between the anaerobic components of the maximal accumulated oxygen deficit (MAOD) and of the 30-second Wingate anaerobic test (30-WAnT). Nine male physical education students performed: a) a maximal incremental exercise test; b) a supramaximal constant workload test to determine the anaerobic components of the MAOD; and c) a 30-WAnT to measure the peak power (PP) and mean power (MP). The fast component of the excess post-exercise oxygen consumption and blood lactate accumulation were measured after the supramaximal constant workload test in order to determine the contributions made by alactic (ALMET) and lactic (LAMET) metabolism. Significant correlations were found between PP and ALMET (r=0.71; P=0.033) and between MP and LAMET (r=0.72; P=0.030). The study results suggested that the anaerobic components of the MAOD and of the 30-WAnT are similarly applicable in the assessment of ALMET and LAMET during high-intensity exercise.

Effect of carbohydrate availability on time to exhaustion in exercise performed at two different intensities

This study examined the effects of pre-exercise carbohydrate availability on the time to exhaustion for moderate and heavy exercise. Seven men participated in a randomized order in two diet and exercise regimens each lasting 3 days with a 1-week interval for washout. The tests were performed at 50 percent of the difference between the first (LT1) and second (LT2) lactate breakpoint for moderate exercise (below LT2) and at 25 percent of the difference between the maximal load and LT2 for heavy exercise (above LT2) until exhaustion. Forty-eight hours before each experimental session, subjects performed a 90-min cycling exercise followed by 5-min rest periods and a subsequent 1-min cycling bout at 125 percent VO2max/1-min rest periods until exhaustion to deplete muscle glycogen. A diet providing 10 percent (CHOlow) or 65 percent (CHOmod) energy as carbohydrates was consumed for 2 days until the day of the experimental test. In the exercise below LT2, time to exhaustion did not differ between the CHOmod and the CHOlow diets (57.22 ± 24.24 vs 57.16 ± 25.24 min). In the exercise above LT2, time to exhaustion decreased significantly from 23.16 ± 8.76 min on the CHOmod diet to 18.30 ± 5.86 min on the CHOlow diet (P < 0.05). The rate of carbohydrate oxidation, respiratory exchange ratio and blood lactate concentration were reduced for CHOlow only during exercise above LT2. These results suggest that muscle glycogen depletion followed by a period of a low carbohydrate diet impairs high-intensity exercise performance.