School of Sport and Recreation - Te Kura Hākinakina
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Research in the School of Sport and Recreation covers sport and activity-related areas, as well as performance, nutrition, coaching and human potential. AUT is the home of New Zealand's top sport and fitness facility, AUT Millennium, and the Sports Performance Research Institute New Zealand (SPRINZ) is New Zealand’s number one sports research institute.
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Browsing School of Sport and Recreation - Te Kura Hākinakina by Subject "0606 Physiology"
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- ItemAn Examination of the Associations Between Nutritional Peaking Strategies in Physique Sport and Competitor Characteristics(BMC, 2024-07-15) Homer, Kai A; Cross, Matt R; Helms, Eric RBACKGROUND: Physique athletes are subjectively judged on their on-stage esthetic per their competition division criteria. To succeed, competitors look to acutely enhance their appearance by manipulating nutritional variables in the days leading up to competition, commonly referred to as peak week (PW). Despite their documented wide adoption, PW strategies lack experimental evidence. Further, the relationship between the specific strategies and the characteristics of the competitors who implement them are unknown. The aim of this research was to examine the effect of competitor characteristics on the specific nutritional peaking strategies implemented, the length of these strategies, and the range of daily carbohydrate (CHO) intakes during these strategies. METHODS: A 58-item survey was developed to gather information on peak week nutrition and training practices of physique athletes. A total of 160 respondents above the age of 18 who had competed in the last 5 years completed the nutrition section. The topics analyzed for this paper included competitor demographics, peaking strategies utilized, and PW CHO intakes. Competitor demographics are presented with the use of descriptive statistics. Associations between competitor demographics and peaking strategies implemented, peaking strategy length, and daily CHO intake ranges were assessed using multiple logistic regression, multiple ordinal logistic regression, and linear mixed models, respectively. RESULTS: From the sampled population, ages 24-39 years (71.2%), male (68.8%), natural (65%), and amateur (90%) were the most common characteristics from their respective categories, while mean competition preparation length was 20.35 ± 8.03 weeks (Males: 19.77 ± 7.56 weeks, Females: 21.62 ± 8.93 weeks), competition preparation body mass loss was 11.5 ± 5.56 kg (M: 12.7 ± 5.76 kg, F: 7.16 ± 3.99 kg), and competition body mass was 72.09 ± 15.74 kg (M: 80.15 ± 11.33 kg, F: 54.34 ± 7.16 kg). For males, the highest and lowest daily CHO intake during PW were 489.63 ± 224.03 g (6.22 ± 2.93 g/kg body mass) and 148.64 ± 152.01 g (1.94 ± 2.17 g/kg), respectively, while for females these values were 266.73 ± 131.23 g (5.06 ± 2.67 g/kg) and 94.42 ± 80.72 g (1.81 ± 1.57 g/kg), respectively. CHO back loading (45%) and water loading (40.6%) were the most popular peaking strategies, while the most prevalent peaking strategy length was 7 days (27.2%). None of the competitor characteristics predicted the use of CHO-based peaking strategies nor peaking strategy length. For non-CHO-based strategies, drug-enhanced competitors were more likely to restrict water than non-drug enhanced, while males and professional competitors had greater odds of loading sodium than females and amateurs, respectively. Finally, when comparing the disparity in highest and lowest CHO intakes during peak week, sex was the only significant factor. CONCLUSIONS: The results of this survey provide further information on the nutritional peaking strategies implemented by competitors. Certain characteristics were identified as predictors of sodium loading and water restriction, and the range of daily PW CHO intake. Contrastingly, no associations were found for CHO-based peaking strategies or peaking strategy length. While our analyses may be underpowered, and thus results should be interpreted with caution, it appears the nutritional peaking strategies implemented by physique competitors are seemingly complex and highly individual.
- ItemBody Fat of Competitive Volleyball Players: A Systematic Review with Meta-Analysis(BMC, 2023) Matłosz, Piotr; Makivic, Bojan; Csapo, Robert; Hume, Patria; Mitter, Benedikt; Martínez-Rodríguez, Alejandro; Bauer, PascalBACKGROUND: Reference values of body fat for competitive volleyball players are lacking, making it difficult to interpret measurement results. This review systematically summarized published data on the relative body fat of volleyball players and calculated potential differences between sex, measurement method, and competitive level. METHODS: The protocol followed the Preferred Reported Items for Systematic Reviews and Meta-Analysis guidelines. The literature search was conducted using five electronic databases to retrieve all relevant publications from January 1, 2010, to July 1, 2021. The 63 studies including 2607 players that met the inclusion criteria were analyzed using random-effects models. Data were reported as pooled mean body fat with 95% confidence intervals. RESULTS: Body fat for males and females was 12.8% (11.9-13.8%) and 22.8% (21.9-23.7%), respectively. Body fat was 18.3% (16.3-20.4%) measured via skinfolds, 18.4% (15.6-21.2%) via bioelectrical impedance analysis, 24.2% (20.4-28.0%) via dual-energy x-ray absorptiometry and 21.6% (17.4-25.8%) via densitometry. Regional, national, and international-level players had body fat values of 19.5% (17.8-21.2%), 20.3% (18.6-22.0%), and 17.9% (15.7-20.4%), respectively. When the meta-regression was adjusted for the variables sex, measurement method, and competitive level, a significant difference between sex (p < 0.001), dual-energy x-ray absorptiometry and skinfolds (p = 0.02), and national and international-level players (p = 0.02) was found. However, sensitivity analysis revealed that findings regarding measurement method and competitive level were not robust and should, therefore, be interpreted with caution. CONCLUSIONS: Despite the limitations of published data, this meta-analysis provided pooled values for body fat of male and female volleyball players for different competitive levels and measurement methods.
- ItemDouble Sigmoid Model for Fitting Fatigue Profiles in Mouse Fast- and Slow-Twitch Muscle(WILEY-BLACKWELL, 2008) Cairns, SP; Robinson, D; Loiselle, DSWe present a curve-fitting approach that permits quantitative comparisons of fatigue profiles obtained with different stimulation protocols in isolated slow-twitch soleus and fast-twitch extensor digitorum longus (EDL) muscles of mice. Profiles from our usual stimulation protocol (125 Hz for 500 ms, evoked once every second for 100-300 s) could be fitted by single-term functions (sigmoids or exponentials) but not by a double exponential. A clearly superior fit, as confirmed by the Akaiki Information Criterion, was achieved using a double-sigmoid function. Fitting accuracy was exceptional; mean square errors were typically <1% and r2 > 0.9995. The first sigmoid (early fatigue) involved ∼10% decline of isometric force to an intermediate plateau in both muscle types; the second sigmoid (late fatigue) involved a reduction of force to a final plateau, the decline being 83% of initial force in EDL and 63% of initial force in soleus. The maximal slope of each sigmoid was seven- to eightfold greater in EDL than in soleus. The general applicability of the model was tested by fitting profiles with a severe force loss arising from repeated tetanic stimulation evoked at different frequencies or rest periods, or with excitation via nerve terminals in soleus. Late fatigue, which was absent at 30 Hz, occurred earlier and to a greater extent at 125 than 50 Hz. The model captured small changes in rate of late fatigue for nerve terminal versus sarcolemmal stimulation. We conclude that a double-sigmoid expression is a useful and accurate model to characterize fatigue in isolated muscle preparations. © 2008 The Authors.
- ItemModeling the Repetitions-in-Reserve-Velocity Relationship: A Valid Method for Resistance Training Monitoring and Prescription, and Fatigue Management.(Wiley Periodicals LLC, 2024-03) Jukic, Ivan; Prnjak, Katarina; Helms, Eric R; McGuigan, Michael REstablishing a relationship between repetitions left in reserve and the mean absolute velocity (RIR-velocity relationship) during resistance training (RT) could allow for objective monitoring, prescription, and real-time adjustment of the training load and set-volume. Therefore, we examined the goodness of fit and prediction accuracy of general and individual RIR-velocity relationships in the free-weight back squat exercise. The effects of sex, training status and history, as well as personality traits, on the goodness of fit and the accuracy of these relationships were also investigated. Forty-six resistance-trained people (15 females and 31 males) performed a one-repetition maximum (1RM) test, and two repetitions to failure (RTF) tests 72 h apart. We found greater goodness of fit of individual RIR-velocity relationships compared to general RIR-velocity relationships. Individual, but not general RIR-velocity relationships established in the first testing session yielded acceptable prediction accuracy of RIR (mean error <2 repetitions) in the subsequent testing session, regardless of the load used. Similar results were obtained when both general and individual RIR-velocity relationships were averaged across the loads, suggesting that a single RIR-velocity relationship covering a range of loads can be used instead of traditional RT methods, potentially allowing for better fatigue management and more efficient adaptation.
- ItemNatural Killer Cell Subset Count and Antigen-Stimulated Activation in Response to Exhaustive Running Following Adaptation to a Ketogenic Diet(Wiley, 2023-02-26) Shaw, David M; Keaney, Lauren; Maunder, Ed; Dulson, Deborah KNew Findings: What is the central question of this study? Does a ketogenic diet (KD) modulate circulating counts of natural killer (NK) cells, including CD56bright and CD56dim subsets, and their ability to activate (CD69 expression) following in vitro antigen stimulation in response to exhaustive moderate-intensity exercise? What is the main finding and its importance? The KD amplified the biphasic exercise-induced NK cell response due to a greater mobilisation of the cytotoxic CD56dim subset but did not alter NK cell CD69 expression. The KD appears to modulate exercise-induced circulating NK cell mobilisation and egress, but not antigen-stimulated circulating NK cell activation. Abstract: We investigated the effect of a 31-day ketogenic diet (KD) compared with a habitual, carbohydrate (CHO)-based diet on total circulating natural killer (NK) CD3−CD56+, dim and bright subset count, and antigen-stimulated CD3−CD56+ cell activation (CD69+) in response to exhaustive running. In a randomised, repeated-measures, cross-over study, eight trained, male endurance athletes ingested a 31-day low-CHO KD or their habitual diet (HD). On day 31, participants ran to exhaustion at 70% (Formula presented.) (∼3.5–4 h, ∼45–50 km). A low-CHO (<10 g) meal was ingested prior to the KD trial, with fat ingested during exercise. A high-CHO (2 g kg−1) meal was ingested prior to the HD trial, with CHO (∼55 g h−1) ingested during exercise. Venous blood samples were collected at pre-exercise, post-exercise and 1 h post-exercise. The KD amplified the classical exercise-induced biphasic CD3−CD56+ cell response by increasing the post-exercise counts (P = 0.0004), which appeared to be underpinned by the cytotoxic CD3−CD56dim subset (main effect of time point, P < 0.0001). The KD had no effect on NK cells’ expression of CD69 or their geometric mean fluorescence intensity of CD69 expression, either for unstimulated or for antigen-stimulated NK cells (all P > 0.05). In conclusion, adaptation to a KD may alter the number of circulating NK cells but not their ability to activate to an antigenic challenge.
- ItemSkeletal Muscle Proteins Involved in Fatty Acid Transport Influence Fatty Acid Oxidation Rates Observed During Exercise(Springer Science and Business Media LLC, 2023-07-14) Maunder, Ed; Rothschild, Jeffrey A; Fritzen, Andreas M; Jordy, Andreas B; Kiens, Bente; Brick, Matthew J; Leigh, Warren B; Chang, Wee-Leong; Kilding, Andrew ESeveral proteins are implicated in transmembrane fatty acid transport. The purpose of this study was to quantify the variation in fatty acid oxidation rates during exercise explained by skeletal muscle proteins involved in fatty acid transport. Seventeen endurance-trained males underwent a (i) fasted, incremental cycling test to estimate peak whole-body fatty acid oxidation rate (PFO), (ii) resting vastus lateralis microbiopsy, and (iii) 2 h of fed-state, moderate-intensity cycling to estimate whole-body fatty acid oxidation during fed-state exercise (FO). Bivariate correlations and stepwise linear regression models of PFO and FO during 0-30 min (early FO) and 90-120 min (late FO) of continuous cycling were constructed using muscle data. To assess the causal role of transmembrane fatty acid transport in fatty acid oxidation rates during exercise, we measured fatty acid oxidation during in vivo exercise and ex vivo contractions in wild-type and CD36 knock-out mice. We observed a novel, positive association between vastus lateralis FATP1 and PFO and replicated work reporting a positive association between FABPpm and PFO. The stepwise linear regression model of PFO retained CD36, FATP1, FATP4, and FABPpm, explaining ~87% of the variation. Models of early and late FO explained ~61 and ~65% of the variation, respectively. FATP1 and FATP4 emerged as contributors to models of PFO and FO. Mice lacking CD36 had impaired whole-body and muscle fatty acid oxidation during exercise and muscle contractions, respectively. These data suggest that substantial variation in fatty acid oxidation rates during exercise can be explained by skeletal muscle proteins involved in fatty acid transport.
- ItemTime Course of Recovery Across Various Compound Resistance Exercises and the Relationship Between Cell-Free DNA and Performance(Wiley, 2019-04-01) Johnson, Trevor K; Belcher, Daniel J; Sousa, Colby A; Carzoli, Joseph P; Visavadiya, Nishant P; Helms, Eric R; Zoeller, Robert F; Whitehurst, Michael; Zourdos, Michael Christopher*This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal. In practice, the deadlift is perceived to require a longer recovery time than the squat or bench press. However, the time course of recovery has not yet between compared between these three exercises. Further, recent data have indicated an inverse relationship between cell-free DNA (cfDNA) and exercise performance, however, these relationships are preliminary. PURPOSE The purpose of this investigation was to examine the magnitude of muscle damage and subsequent recovery time between the squat, bench press, and deadlift. METHODS Twelve males (age: 24.5±3.8yrs, body mass: 84.01±15.44kg, height: 173.43±8.57cm, training age: 7.1±4.2yrs) performed 4 sets to failure at 80% of a one-repetition maximum (1RM) on the squat, bench press, and deadlift in successive weeks; in a counterbalanced order. Measures of indirect muscle damage and performance fatigue were assessed immediately prior to, post-exercise, and 24, 48, 72, and 96hrs post-exercise. Outcome measures were delayed onset muscle soreness (DOMS), average concentric velocity (ACV) at 70% of 1RM, creatine kinase (CK), lactate dehydrogenase (LDH), and cfDNA. RESULTS There were no between condition differences for changes in CK, LDH, or DOMS (p>0.05). However, ACV decreased in the squat condition for up to 72 hours (p=0.02, −8.61%) and in the bench press (p<0.01, −26.69%) immediately post-exercise, but did not decrease in the deadlift condition (p>0.05). There was a main time effect for increased cfDNA in the squat (p<0.01) and bench press (p<0.05), but not the deadlift (p=0.153). Further, there were various significant (p<0.05) and positive relationships between cfDNA and ACV during the recovery period. Specifically, immediately post-exercise changes in cfDNA were positively related changes in post-exercise ACV the squat (r=0.64, p=0.02). Further, immediately post-exercise changes in cfDNA were significantly related to deadlift ACV or approached a significant relationship with deadlift ACV at every recovery time point (immediate: r=0.52, p=0.09; 24hrs: r=0.66, p=0.02; 48hrs: r=0.73, p=0.01; 72hrs: r=0.64, p=0.03; 96hrs: r=0.66, p=0.02). CONCLUSION These results suggest that the deadlift does not require a longer recovery period than the squat or bench press following high volume training to failure in well-trained men. Further, changes in post-exercise cfDNA may predict velocity of resistance exercise performance throughout a 96-hour recovery period. Importantly, we observed direct relationships between cfDNA and performance, while a previous investigation has reported inverse relationships in this respect. Of note, our immediately post blood collection occurred ~10 minutes post-exercise, thus it is possible there was an increase in DNase activity, resulting in a decrease in serum cfDNA during the 10-minute window between the end of exercise and blood collection. Further, DNase kinetics have considerable individual variation and may account for some disparities.