This study aimed to examine the validity, reliability and minimum detectable change (MDC) of the Cosmed K5 in breath by breath (BxB) mode, against VacuMed metabolic simulator. Intra and inter-units reliability was also assessed. Fourteen metabolic rates (from 0.9 to 4 L.min-1) were reproduced by a VacuMed system and pulmonary ventilation (VE), oxygen consumption (VO₂) and carbon dioxide production (VCO₂) were measured by two different K5 units. Validity was assessed by ordinary least products (OLP) regression analysis, Bland-Altman plots, intraclass correlation coefficients (ICC), mean percentage differences, technical errors (TE) and MDC for VE, VO₂, and VCO₂. Intra- and inter-K5 reliability was evaluated by absolute percentage differences between measurements (MAPE), ICCs, TE, and MDC. Validity analysis from OLP regression data and Bland- Altman plots indicated high agreement between K5 and simulator. ICC values were excellent for all variables (>0.99). Mean percentage differences in VE (-0.50%, p = 0.11), VO₂ (-0.04%, p = 0.80), and VCO₂ (-1.03%, p = 0.09) showed no significant bias. The technical error (TE) ranged from 0.73% to 1.34% (VE and VCO₂ respectively). MDC were lower than 4% (VE = 2.0%, VO₂ = 3.8%, VCO₂ = 3.7%). The intra and inter K5 reliability assessment reveled excellent ICCs (>0.99), MAPE <2% (no significant differences between trials), TE < or around 1%, MDC <or around 3%. K5 in BxB mode is a valid and reliable system for metabolic measurements. This is the first study assessing the MDC accounting only for technical variability reporting intra- and inter-units MDCs <3.3%.

The aim of this study was to compare match analysis (using video recordings) and the physiological load (heart rate measured every 5s, blood lactate measured after the warm-up, first half and second half) of six 11-year-old soccer players during official games of eleven-a-side on a regular-sized pitch (100×65m) and of seven-a-side on a smaller pitch (60×40m). In both games, heart rate exceeded 170 beats·min-1 84% of the time, while blood lactate ranged from 1.4 to 8.1 mmol·l-1 . No significant differences were recorded for the physiological parameters. For both matches, walking comprised 38% of total time, running 55%, inactivity 3% and jumping 3%. Although there were no significant differences between halves or matches, running for less than 10s was 10% more frequent in the seven-a-side game. In the seven-a-side game, there were significantly more passes and significantly fewer tackles, suggesting that seven-a-side matches played on smaller pitches may be more suitable for pre-pubescent soccer players.

E conducted in laboratories, and consequently, the external validity of the findings may be questionable. Purpose: To determine whether environmental settings (treadmill vs overground) differentially influence physiological, perceptual, and affective responses to exercise at a self-selected pace. Methods: Thirty-four individuals (17 men and 17 women) between 18 and 30 yr volunteered to participate in this study. During the orientation session, individuals underwent an initial screening, anthropometric measurements, and familiarization with the experimental procedures. Next, subjects underwent a maximal treadmill test. In the two experimental trials, participants performed 20-min bouts of treadmill and overground walking at a self-selected pace, which were completed in a counterbalanced order. At least 48 h separated experimental trials. Results: Using repeated-measures ANOVA, overground walking speed was significantly faster than treadmill walking speed (P < 0.01) during the 20-min bout of self-paced exercise. However, exercise intensity (%V˙O2R and %HRR) and perceived exertion during the session of overground walking were significantly lower (P < 0.05) when compared with those during the treadmill session. In addition, affective valence was more positive during the session of overground walking than during the treadmill session (P < 0.01). Conclusions: These data extend previous findings by showing that environmental setting influences physiological, perceptual, and affective responses during exercise at a self-selected pace. Self-paced exercise performed over ground resulted in lower perceptual and more positive affective responses....

Blood mononuclear cells (PBMCs). Methods This work investigated whether acute exercise modulates the expression of BDNF, pro-BDNF, and p75NTR in the PBMCs of 10 healthy young men who performed a cycling incremental test to exhaustion (MAX) or exercised at individual anaerobic threshold (IAT). The PBMC expression of stress response proteins and the level of circulating BDNF, vascular endothelial growth growth factor, platelet-derived growth factor subunit B, basic fibroblast growth factor pro-inflammatory, and anti-inflammatory cytokines were analyzed as well. Results A major finding is that both sessions of acute exercise regulated the content of BDNF isoforms within PBMCs in a manner related to the physiological stress exerted. Although the pro-BDNF increased after both MAX and IAT protocols, BDNF showed a kinetics dependent on exercise type: MAX induced a 54% protein increase immediately after exercise, followed by a significant drop 60 min after its conclusion (38% lower than the baseline). Differently, in the IAT, BDNF increased significantly up to 75% from the baseline throughout the recovery phase. All physiological parameters, as well as the p75NTR receptor and the stress-inducible proteins, were also differently regulated by the two exercise conditions. Conclusions These data supported the hypothesis that PBMCs might produce and secrete BDNF isoforms, as well as modulate the proteins p75NTR, Bcl-xL, hsp90, hsp27, and αB-crystallin, as part of the physiological stress response induced by acute exercise, offering a novel example of bidirectional interaction between nervous and immune systems....