This study assessed the reliability of a 'self-paced' 30-min, team-sport running protocol on a Woodway Curve 3.0 non-motorised treadmill (NMT). Ten male team-sport athletes (20.3 ± 1.2 y, 74.4 ± 9.7 ...kg, VO2peak 57.1 ± 4.5 ml·kg(-1)·min(-1)) attended five sessions (VO2peak testing + familiarisation; four reliability trials). The 30-min protocol consisted of three identical 10-min activity blocks, with visual and audible commands directing locomotor activity; however, actual speeds were self-selected by participants. Reliability of variables was estimated using typical error ± 90% confidence limits expressed as a percentage coefficient of variation (CV) and intraclass correlation coefficient. The smallest worthwhile change (SWC) was calculated as 0.2 × between participant standard deviation. Peak/mean speed and distance variables assessed across the 30-min protocol exhibited a CV < 5%, and < 6% for each 10-min activity block. All power variables exhibited a CV < 7.5%, except walking (CV 8.3-10.1%). The most reliable variables were maximum and mean sprint speed (CV < 2%). All variables produced a CV% greater than the SWC. A self-paced, team-sport running protocol performed on a NMT produces reliable speed/distance and power data. Importantly, a single familiarisation session allowed for adequate test-retest reliability. The self-paced design provides an ecologically-valid alternative to externally-paced team-sport running simulations. Key pointsSelf-paced team-sport running protocols on a curved NMT that closely match the locomotor demands of competition deliver reliable test-retest measures of speed, distance and power.Such protocols may be sensitive to changes in running profile following an intervention that may not be detectable during externally-paced protocols.One familiarisation session is adequate to ensure test-retest reliability.
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DOBA, FSPLJ, IZUM, KILJ, NUK, OILJ, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK, VSZLJ
PURPOSEExercise in hot conditions increases core (TC) and skin temperature (TSK) and can lead to a progressive rise in HR and decline in stroke volume (SV) during prolonged exercise. ...Thermoregulatory-driven elevations in skin blood flow (SkBF) adds complexity to cardiovascular regulation during exercise in these conditions. Presently, the dominant, although debated, view is that raising TSK increases SkBF and reduces SV through diminished venous return; however, this scenario has not been rigorously investigated across core and skin temperatures. We tested the hypothesis that high TSK would raise HR and reduce SV during exercise after precooling (cold water bath) and preheating (hot water bath) and that no relationship would exist between SkBF and SV during exercise.
METHODSNon–endurance-trained individuals cycled for 20 min at 69% ± 1% V˙O2peak on four occasionscool skin–cool core (SkCCC), warm skin–cool core (SkWCC), cool skin–warm core (SkCCW), and warm skin–warm core (SkWCW) on separate days.
RESULTSAfter precooling of TC, the rise in HR was greater in SkWCC than in SkCCC (P < 0.001), yet SV was similar (P = 0.26), which resulted in higher QC at min 20 in SkWCC (P < 0.01). Throughout exercise after preheating of TC, HR was higher (P < 0.001), SV was reduced (P < 0.01), and QC was similar (P = 0.40) in SkWCW versus SkCCW. When all trials were compared, there was no relationship between SkBF and SV (r = −0.08, P = 0.70); however, there was an inverse relationship between HR and SV (r = −0.75, P < 0.001).
CONCLUSIONSThese data suggest that when TSK is elevated during exercise, HR and TC will rise but SV will only be reduced when TC is also elevated above 38°C. Furthermore, changes in SV are not related to changes in SkBF.
Little research has been done on the physiological and performance effects of altitude training on team-sport athletes. Therefore, this study examined changes in 2000-m time-trial running performance ...(TT), hemoglobin mass (Hbmass), and intramuscular carnosine content of elite Australian Football (AF) players after a preseason altitude camp.
Thirty elite AF players completed 19 days of living and training at either moderate altitude (~2130 m; ALT, n = 21) or sea level (CON, n = 9). TT performance and Hbmass were assessed preintervention (PRE) and postintervention (POST1) in both groups and at 4 wk after returning to sea level (POST2) in ALT only.
Improvement in TT performance after altitude was likely 1.5% (± 4.8-90%CL) greater in ALT than in CON, with an individual responsiveness of 0.8%. Improvements in TT were maintained at POST2 in ALT. Hbmass after altitude was very likely increased in ALT compared with CON (2.8% ± 3.5%), with an individual responsiveness of 1.3%. Hbmass returned to baseline at POST2. Intramuscular carnosine did not change in either gastrocnemius or soleus from PRE to POST1.
A preseason altitude camp improved TT performance and Hbmass in elite AF players to a magnitude similar to that demonstrated by elite endurance athletes undertaking altitude training. The individual responsiveness of both TT and Hbmass was approximately half the group mean effect, indicating that most players gained benefit. The maintenance of running performance for 4 wk, despite Hbmass returning to baseline, suggests that altitude training is a valuable preparation for AF players leading into the competitive season.
ABSTRACTMcLean, BD, Petrucelli, C, and Coyle, EF. Maximal power output and perceptual fatigue responses during a Division I female collegiate soccer season. J Strength Cond Res 26(12)3189–3196, ...2012—The purpose of this study was to investigate how maximal power output (PMAX), as measured via the inertial load cycling technique, changes throughout a collegiate soccer season in relation to training load completed. The current investigation took place throughout the 2010 Big XII soccer season. Nineteen Division I female collegiate soccer players (age19.9 ± 1.2 years, stature165.1 ± 6.6 cm, mass61.0 ± 6.8 kg) from the same team completed regular inertial load cycling tests and perceptual fatigue questionnaires throughout the season. Players were divided into STARTERS and NON-STARTERS based on percentage of matches started throughout the season. The results demonstrated that STARTERS experience much greater load throughout the season than NON-STARTERS (2247 ± 176 arbitrary units AU and 1585 ± 174 AU, p < 0.05), accounted for by increased load during matches. This increased load throughout the season was accompanied by decline in PMAX in STARTERS (to 92.3 ± 6.6%, p < 0.05), whereas PMAX was maintained in NON-STARTERS for the duration of the season (99.0 ± 4.9%). Furthermore, STARTERS experienced greater muscle soreness throughout the in-season period compared with NON-STARTERS. The main finding of this study is that PMAX declined throughout the middle and latter parts of the season in STARTERS, after experiencing significantly greater match loads than NON-STARTERS throughout the season. The current findings, combined with previous investigations, suggest that load needs to be carefully monitored throughout the in-season period to maintain optimal neuromuscular performance throughout a teamʼs entire sporting season.
ABSTRACTMcLean, BD, Tofari, PJ, Gore, CJ, and Kemp, JG. Changes in running performance after four weeks of interval hypoxic training in Australian footballersA single-blind placebo-controlled study. ...J Strength Cond Res 29(11)3206–3215, 2015—There is a paucity of data examining the impact of high-intensity interval hypoxic training (IHT) on intermittent running performance. This study assessed the effects of IHT on 17 amateur Australian Footballers, who completed 8 interval treadmill running sessions (IHT FIO2 = 15.1% or PLACEBO) over 4 weeks, in addition to normoxic football (2 per week) and resistance (2 per week) training sessions. To match relative training intensity, absolute IHT intensity reduced by 6% of normoxic vVCombining Dot AboveO2peak compared with PLACEBO. Before and after the intervention, performance was assessed by Yo-Yo intermittent recovery test level 2 (Yo-Yo IR2) and a self-paced team sport running protocol. Standardized effect size statistics were calculated using Cohenʼs d to compare between the interventions. Compared with PLACEBO, IHT subjects experienced (a) smaller improvements in Yo-Yo IR2 performance (Cohenʼs d = −0.42 −0.82 to −0.02; 90% confidence interval); (b) similar increases in high-intensity running distance during the team sport protocol (d = 0.17 −0.50 to 0.84); and (c) greater improvements in total distance (d = 0.72 0.33–1.10) and distance covered during low-intensity activity (d = 0.59 −0.07 to 1.11) during the team sport protocol. The lower absolute training intensity of IHT may explain the smaller improvements in Yo-Yo IR2 performance in the hypoxic group. Conversely, the data from the self-paced protocol suggest that IHT may positively influence pacing strategies in team sport athletes. In conclusion, IHT alters pacing strategies in team sport athletes (i.e., increased distance covered during low-intensity activity). However, IHT leads to smaller improvements in externally paced high-intensity intermittent running performance (i.e., Yo-Yo IR2), which may be related to a reduced absolute training intensity during IHT sessions.
A colorimetric method is described for measuring glucose consumption by tissue culture cells. This procedure, which utilizes the coupled activities of glucose oxidase and horseradish peroxidase, is ...insensitive to the spectral interferences caused by the phenol red and sera present in most tissue culture media. The spectral properties (absorbance maxima and apparent absorption coefficients) and stability of a large number of chromogenic horseradish peroxidase substrates were surveyed for their ability to perform in an assay for glucose in the presence of phenol red and sera components. One of these chromophores, the product of an oxidative couple between 4-aminoantipyrine and N-ethyl-N-sulfopropyl-m-toluidine, was subsequently used to develop a fixed time assay for glucose in media samples. The assay required only 10 microliters of media in a 1-ml assay volume; reproducibility studies showed variabilities of less than 5% in the assay of a single sample, and values obtained in glucose analyses correlated well with those obtained using commercially available test kits. The assay was used to study the rate of glucose consumption in two different cell types, bovine corneal endothelial cells and human diploid fibroblasts.
Protein synthesis and deposition by vascular endothelial cells play an important role in the neovascularization seen in diabetic retinopathy. In the present study, we have compared the pattern of ...protein accumulation in human retinal endothelial cells derived from diabetic and nondiabetic individuals. Confluent cultures of retinal endothelial cells were incubated for 18 h with a mixture of radiolabeled methionine and cysteine. Under basal conditions, without the addition of growth factors, diabetic retinal endothelial cells accumulated less radiolabeled protein than did cells of nondiabetic origin. Both epidermal growth factor (EGF) and basic fibroblast growth factor (bFGF) enhanced protein accumulation in cells of diabetic origin, but not in cells of nondiabetic origin. Analysis of radiolabeled proteins in the secreted fraction by sodium dodecyl sulfate (SDS) polyacrylamide gel electrophoresis (PAGE) revealed prominent protein bands at 220 and 49.5 kD in both diabetic and nondiabetic cultures that were identified by immunoblot analysis as fibronectin and a mixture of secreted protein acidic and rich in cysteine (SPARC) and plasminogen activator inhibitor-1 (PAI-1), respectively. The levels of PAI-1 were higher in the secreted fractions of diabetic cultures than in nondiabetic cultures. SDS-PAGE and autoradiography of the secreted fraction also revealed two protein components of approximate molecular weight 440 and 78 kD, which were present in fractions of diabetic origin but absent in those of nondiabetic origin. Our studies support unique differences in protein expression in cells of diabetic vs. nondiabetic origin in response to EGF and bFGF and identify two proteins exclusively expressed by cells of diabetic origin.
Although high-performance liquid chromatography has been used extensively to characterize the glycosaminoglycan chains of proteoglycans, very few researchers have reported the use of this technology ...for the separation of intact proteoglycan species. The high molarity denaturing buffers required for proteoglycan disaggregation and separation are often not compatible with the low back-pressure limitations imposed by many of the HPLC systems designed for the separation of biological macromolecules. In this study, heparan sulfate and dermatan sulfate proteoglycans, obtained by the metabolic labeling of cultured corneal endothelial cells, were rapidly and completely separated in less than an hour in a high-pressure liquid chromatography system. The separation, which used a Dionex BioLC system equipped with a Pharmacia Superloop and a ProPac PA1 column, also effected a greater than 10-fold concentration of the proteoglycans during the separation procedure. All buffers were 8 M in urea, and the back-pressures generated during the separation were well below the limit of the system. The pooled fractions from the ion-exchange column were subsequently analyzed for glycosaminoglycan composition and molecular size. The system was able to resolve dermatan sulfate-substituted species from heparan sulfate-substituted species in a single chromatographic step. The proteoglycan nature of the recovered products was established by Sepharose CL-4B chromatography and gel electrophoresis.
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