School of Sport and Recreation - Te Kura Hākinakina

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https://hdl.handle.net/10292/1542
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 "06 Biological Sciences"

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    The Effects of Regional Quadriceps Architecture on Angle-Specific Rapid Force Expression
    (Canadian Science Publishing, 2023-06-30) Oranchuk, Dustin J; Hopkins, William G; Cronin, John B; Storey, Adam G; Nelson, André R
    Evaluating anatomical contributions to performance can increase understanding of muscle mechanics and guide physical preparation. While the impact of anatomy on muscular performance is well studied, the effects of regional quadriceps architecture on rapid torque or force expression are less clear. Regional (proximal, middle, distal) quadriceps (vastus lateralis, rectus femoris, and vastus intermedius) thickness (MT), pennation angle (PA), and fascicle length (FL) of 24 males (48 limbs) were assessed via ultrasonography. Participants performed maximal isometric knee extensions at 40º, 70º, and 100º of knee flexion to evaluate rate of force development from 0-200 ms (RFD0-200). Measurements were repeated on three occasions with the greatest RFD0-200 and mean muscle architecture measures used for analysis. Linear regression models predicting angle-specific RFD0-200 from regional anatomy provided adjusted correlations (√adjR2) with bootstrapped compatibility limits. Mid-rectus femoris MT (√adjR2=0.41-0.51) and proximal-vastus lateralis FL (√adjR2=0.42-0.48) were the best single predictors of RFD0-200, and the only measures to reach precision with 99% compatibility limits. Small simple correlations were found across all regions and joint angles between RFD0-200 and vastus lateralis MT (√adjR2=0.28±0.13; mean±SD), vastus lateralis FL (√adjR2=0.33±0.10), rectus femoris MT (√adjR2=0.38±0.10), and lateral vastus intermedius MT (√adjR2=0.24±0.10). Between-correlation comparisons are reported within the article. Researchers should measure mid-region rectus femoris MT and vastus lateralis FL to efficiently and robustly evaluate potential anatomical contributions to rapid knee extension force changes, with distal and proximal measurements providing little additional value. However, correlations were generally small to moderate, suggesting that neurological factors may be critical in rapid force expression.
  • Item
    Weight Loss Induces Changes in Adaptive Thermogenesis in Female and Male Physique Athletes
    (Canadian Science Publishing, 2023-01-16) Isola, Ville; Hulmi, Juha J; Petäjä, Pirita; Helms, Eric R; Karppinen, Jari E; Ahtiainen, Juha P
    Physique athletes lose substantial weight preparing for competitions, potentially altering systemic metabolism. We investigated sex differences in body composition, resting energy expenditure (REE), and appetite-regulating and thyroid hormone changes during a competition preparation among drug-free physique athletes. The participants were female (10 competing (COMP) and 10 non-dieting controls (CTRL)) and male (13 COMP) and 10 CTRL)) physique athletes. COMP were tested before they started their diet 23 weeks before competing (PRE), during their diet one week before competing (MID), and 23 weeks after competing (POST) whereas CTRL were tested at similar intervals but did not diet. Measurements included body composition by DXA, muscle size, and subcutaneous fat thickness (SFA) by ultrasound, REE by indirect calorimetry, circulating ghrelin, leptin T3, and T4 hormone analysis. Fat mass (FM) and SFA decreased in both sexes (p<0.001), while males (p<0.001) lost more lean mass (LM) than females (p<0.05). Weight loss, decreased energy intake, and increased aerobic exercise (p<0.05) led to decreased LM and FM-adjusted REE (p<0.05), reflecting metabolic adaptation. Absolute leptin levels decreased in both sexes (p<0.001) but more among females (p<0.001) due to higher baseline leptin levels. These changes occurred with similar decreases in T3 (p<0.001) and resting heart rate (p<0.01) in both sexes. CTRL, who were former or upcoming physique athletes, showed no systematic changes in any measured variables. In conclusion, while dieting, female and male physique athletes experience REE and hormonal changes leading to adaptive thermogenesis. However, responses seemed temporary as they returned toward baseline after the recovery phase. ClinicalTrials.gov (NCT04392752).
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