High intensity cycle ergometer exercise tests are designed to measure power outputs. Most of the tests utilise resistive forces that are based on total-body mass values (TBM). Conceptually, selecting an optimal resistive force based on total-body mass may not be the best approach. Resistive forces that reflect the mass of the lean tissue specifically involved in the performance of the diagnostic task may be more appropriate. To investigate this theory the following studies were proposed. STUDY ONE. To identify the upper body contribution to a cycle ergometer test via the handgrip. STUDY TWO. To examine any differences in power profiles, when loading procedures were based on total-body mass (TBM) or fat-free mass (FFM). STUDY THREE. To investigate the sympathoadrenergic and blood lactate responses, when loading procedures were based on total-bodymass (TBM) or fat-free mass (FFM).STUDY FOUR. To measure blood concentrations of, lipidhydroperoxides (LH), malondialdehyde (MDA), creatine kinase (CK)and myoglobin (Mb) that may occur when resistive forces were based on total-body mass (TBM) or fat-free mass (FFM). STUDY ONEIndices of mechanical power output were obtained from twelve subjects during high intensity leg cycle ergometry tests (20 second duration; 75 grams per kilogram total-body mass) using two protocols:one with a standard handle-bar grip (with - grip), and one with supinated wrists (without - grip). Peak mechanical power, mean mechanical power, fatigue index and total mechanical work values were calculated for each subject during each test, and the sample mean differences associated with the two protocols were compared using paired Student t-tests. The with-grip protocol yielded significantly greater peak mechanical power output and greater fatigue index than the without - grip protocol(886 ± 124 W vs 815 ± 151 W, respectively; and 35 ± 10% vs 25 ±8%, respectively ; P < 0.05}. The electrical activity of the anterior forearm musculature was measured in the twelfth subject during the performance of each of the test protocol in an initial attempt to quantify any differences in muscular activity between protocols. While peak mechanical power output was greater during the with - grip protocol,than during the without - grip protocol, the electromyographs showed much greater forearm muscle activity during the with - grip protocol. Thus the protocol which allowed for the greatest measure of peak leg power output was also associated with considerable arm muscle activity. These findings should be considered when blood samples are taken from the arm for the biochemical analysis of cycling tasks. STUDY TWOStudy two compared the maximal exercise performance of 10 men during friction braked cycle ergometry of 20 s duration when resistive forces reflected total-body mass (TBM) or fat-free mass (FFM). Fat mass was calculated from the sum of skinfold thicknesses. Increases(P < 0.05) in peak power output (PPO) were found between TBM and FFM (1015 ± 165 W TBM vs 1099 ± 172 W FFM). Decreases (P <0.05) were observed for the time taken to reach PPO (3.8 ± 1.4 s TBMvs 2.9 ± 1 s FFM). Pedal velocity increased (P < 0.05) during the FFM protocol (129.4 ± 8.2 rpm TBM vs 136.3 ± SrpmFFM). Rating of perceived exertion (RPE) was also (P < 0.05) greater for FFM (18.4 ± 1.6 TBM vs 19.8 ± 0.4 FFM). No changes were found for Mean Power Output (MPO), fatigue index (FI) or Work Done(WD) between trials. These findings suggest that high intensity resistive force loading protocols may need to be reconsidered. Results from this study indicate that the active tissue component of body composition needs consideration in resistive force selection when ascertaining maximal cycle ergometer power profiles. STUDY THREEThe purpose of study three was to compare the sympathoadrenergic and blood lactate responses to maximal exercise performance during 30s cycle ergometry when resistive forces were dependent on total-bodymass (TBM) and fat-free mass (FFM). Correlations (P < 0.05) were recorded between PPOs, and immediate post-exercise noradrenaline concentrations for both the TBM and FFM protocols. Increases (P < 0.05) in the concentrations of adrenaline, noradrenaline and lactate from rest to immediately post exercise were observed for both the TBM and FFM protocols, with decreases in concentration noted (P < 0.05) immediately post to 24 h post exercise (see table 6.3). There were no differences (P > 0.05) recorded between TBM and FFM during any of the blood sampling stages. These results are interesting when we consider that with increases in PPO recorded for the FFM protocol there were no differences between protocols in the estimation of neurophysiological and metabolic stress as determined by plasmaadrenaline, noradrenaline and blood lactate concentrations. STUDY FOUR. Study four compared power outputs, and blood levels of, lipidhydroperoxides (LH), malondialdehyde (MDA), creatine kinase (CK), myoglobin (Mb) and lactate ([La-]g) following 30 s of maximal cycleergometry exercise when resistive forces were dependent on total-bodymass (TBM) or fat-free mass (FFM). Alpha-tocopherol, Retinol and uric acid concentrations were also measured to quantify the activity of selected antioxidants. Cardiac troponin concentrations (cTnl) were also determined to exclude protein leakage from the myocardium. Increases in CK activity was recorded from rest to immediately post exercise during both the TBM and FFM protocols (P < 0.05 ; P < 0.05 respectively) and decreased from immediately post to 24 h post exercise during the FFM protocol only. LH increased from rest to immediately post exercise for both the TBM and FFM protocol (P < 0.05 ; P < 0.05 respectively) and decreased 24 h post exercise for both protocols. Differences in LH concentrations were also observed immediately post exercise between the TBM and FFM protocols (P < 0.05). Increases in MDA concentrations were recorded from rest to immediately post exercise for TBM (P < 0.05), with a decrease recorded from immediate post to 24 h post exercise. Differences in MDA concentrations were recorded between the TBM and FFM protocol immediately post exercise. Differences in TBM and FFM concentrations were also recorded immediately post exercise for Mb (P < 0.05). Blood lactate values([La~]B) increased (P < 0.05) from rest, to immediately post exercise,and returned to resting values 24 h post exercise for both the TBM and FFM. Alpha-tocopherol and uric acid concentrations decreased from rest to immediately post exercise for both TBM and FFM protocols (P < 0.05 ; P < 0.05 respectively) and increased 24 h post exercise. There were no changes observed in Retinol concentrations for any of the blood sampling stages. The results of the study suggest that greater power outputs are obtainable with significantly less muscle damage and oxidative stress when resistive forces reflect FFM mass during loading procedures. This finding may also be related to better force velocity relationships observed for the FFM protocol, ie more efficient mechanics of movement which may result in less strain, and therefore less internal damage. Findings from the study indicate that procedures that produce greater power values, with no difference in stress response, that are less damaging to muscle tissue and relate to the active tissue during this type of exercise, may need to be explored in preference to loading procedures that include both lean and fat masses.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:324739 |
| Date | January 2000 |
| Creators | Baker, Julien Steven |
| Publisher | University of South Wales |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | https://pure.southwales.ac.uk/en/studentthesis/optimisation-considerations-for-the-measurement-of-human-muscle-power(6dd8a26f-b3d9-47c4-8511-90bd35f18ac3).html |
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