Nose-down saddle tilt improves gross efficiency during seated-uphill cycling

o assess the effects of gradient and running speed on efficiency of exercise, and to evaluate contributions of oxidative and anaerobic energy production (Ean) during locomotion, two sets of experiments were performed. The caloric expenditures of rats were determined from O2 consumption (VO2) while they ran at three speeds (13.4, 26.8, and 43.1 m/min) on five grades (1, 5, 10, 15, and 20%). In addition, lactate turnover (LaT) and oxidation (Laox) were determined on rats at rest or during running at 13.4 and 26.8 m/min on 1% grade, respectively. Lactate production not represented in the VO2 (i.e., Ean) was calculated from the LaT not accounted for by oxidation [(LaT an) = LaT-Laox)]. The Ean was calculated as: Ean = [LaT an(mumol/min)] [1.38 ATP/La] [11 mcal/mumol ATP]. Gross efficiency of exercise (the caloric equivalent of external work/caloric equivalent of VO2 X 100) ranged from 1.7 to 4.5%. Apparent efficiency (the inverse of the regression of caloric equivalent of VO2 on the caloric equivalent of work X 100) ranged from 20.5 to 26.4% and reflected the metabolic response of rats to applied external work. The contribution of Ean to total energy turnover ranged from 1.6% at rest to 0.8% during running at 13.4 m/min on a 1% grade. Despite active LaT during steady-state exercise, Ean contributes insignificantly to total energy transduction, because over 70% of the lactate produced is removed through oxidation. VO2 adequately represents metabolism under these conditions.

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Variations in exercise ventilation in hypoxia will affect oxygen uptake

Physiology International ◽

10.1556/2060.2020.00031 ◽

2020 ◽

Vol 107 (3) ◽

pp. 431-443

Author(s):

J.A. Loeppky ◽

R.M. Salgado ◽

A.C. Sheard ◽

D.O. Kuethe ◽

C.M. Mermier

Keyword(s):

Individual Variation ◽

Ambient Pressure ◽

Work Of Breathing ◽

Linear Equations ◽

Mechanical Efficiency ◽

Individual Response ◽

Hypoxic Ventilatory Response ◽

Gross Efficiency ◽

Exercise Ventilation ◽

Progressive Exercise

AbstractReports of VO2 response differences between normoxia and hypoxia during incremental exercise do not agree. In this study VO2 and VE were obtained from 15-s averages at identical work rates during continuous incremental cycle exercise in 8 subjects under ambient pressure (633 mmHg ≈1,600 m) and during duplicate tests in acute hypobaric hypoxia (455 mmHg ≈4,350 m), ranging from 49 to 100% of VO2 peak in hypoxia and 42–87% of VO2 peak in normoxia. The average VO2 was 96 mL/min (619 mL) lower at 455 mmHg (n.s. P = 0.15) during ramp exercises. Individual response points were better described by polynomial than linear equations (mL/min/W). The VE was greater in hypoxia, with marked individual variation in the differences which correlated significantly and directly with the VO2 difference between 455 mmHg and 633 mmHg (P = 0.002), likely related to work of breathing (Wb). The greater VE at 455 mmHg resulted from a greater breathing frequency. When a subject's hypoxic ventilatory response is high, the extra work of breathing reduces mechanical efficiency (E). Mean ∆E calculated from individual linear slopes was 27.7 and 30.3% at 633 and 455 mmHg, respectively (n.s.). Gross efficiency (GE) calculated from mean VO2 and work rate and correcting for Wb from a VE–VO2 relationship reported previously, gave corresponding values of 20.6 and 21.8 (P = 0.05). Individual variation in VE among individuals overshadows average trends, as also apparent from other reports comparing hypoxia and normoxia during progressive exercise and must be considered in such studies.

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The relationship between the gross efficiency and the ability to repeat the given pressure force in trained cyclists

Human Movement ◽

10.5114/hm.2019.79217 ◽

2019 ◽

Vol 20 (1) ◽

pp. 48-54

Author(s):

Rafał Hebisz ◽

Ryszard Błacha ◽

Paulina Hebisz ◽

Stefan Szczepan

Keyword(s):

Pressure Force ◽

Gross Efficiency ◽

The Given ◽

The Relationship

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Energy Expenditure Equation Choice: Effects on Cycling Efficiency and its Reliability

International Journal of Sports Physiology and Performance ◽

10.1123/ijspp.2018-0818 ◽

2020 ◽

Vol 15 (2) ◽

pp. 288-291

Author(s):

Arthur H. Bossi ◽

Wouter P. Timmerman ◽

James G. Hopker

Keyword(s):

Energy Expenditure ◽

Peak Power ◽

Peak Power Output ◽

Physiological Profile ◽

Gas Exchanges ◽

Gross Efficiency ◽

Reliability Parameters ◽

Cycling Efficiency ◽

The Mean ◽

Gas Exchange Threshold

Purpose: There are several published equations to calculate energy expenditure (EE) from gas exchanges. The authors assessed whether using different EE equations would affect gross efficiency (GE) estimates and their reliability. Methods: Eleven male and 3 female cyclists (age 33 [10] y; height: 178 [11] cm; body mass: 76.0 [15.1] kg; maximal oxygen uptake: 51.4 [5.1] mL·kg−1·min−1; peak power output: 4.69 [0.45] W·kg−1) completed 5 visits to the laboratory on separate occasions. In the first visit, participants completed a maximal ramp test to characterize their physiological profile. In visits 2 to 5, participants performed 4 identical submaximal exercise trials to assess GE and its reliability. Each trial included three 7-minute bouts at 60%, 70%, and 80% of the gas exchange threshold. EE was calculated with 4 equations by Péronnet and Massicotte, Lusk, Brouwer, and Garby and Astrup. Results: All 4 EE equations produced GE estimates that differed from each other (all P < .001). Reliability parameters were only affected when the typical error was expressed in absolute GE units, suggesting a negligible effect—related to the magnitude of GE produced by each EE equation. The mean coefficient of variation for GE across different exercise intensities and calculation methods was 4.2%. Conclusions: Although changing the EE equation does not affect GE reliability, exercise scientists and coaches should be aware that different EE equations produce different GE estimates. Researchers are advised to share their raw data to allow for GE recalculation, enabling comparison between previous and future studies.

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138. Effect of Breed, Size of Cow, Yield of Milk and Stage of Lactation upon Efficiency of Milk Production

Journal of Dairy Research ◽

10.1017/s0022029900001771 ◽

1936 ◽

Vol 7 (3) ◽

pp. 211-221 ◽

Cited By ~ 11

Author(s):

Joseph Edwards

Keyword(s):

Milk Production ◽

Milk Yield ◽

Live Weight ◽

Gross Efficiency ◽

Physiological Efficiency ◽

Stage Of Lactation ◽

Actual Yield ◽

The Relationship

The records of 2400 cows on test at the London Dairy Show between the years 1922 and 1934 have been examined for the relationship between the gross physiological efficiency of milk production and the factors of breed, size of cow within a breed, actual yield of milk and stage of lactation. (“Gross Efficiency” is here the ratio of energy in the milk to the energy in the digestible nutrients consumed.)(1) It is shown that among the best representatives of the various dairy breeds there is little difference in gross efficiency of milk production. The lactation stimulus has been bred approximately in proportion to the size of the breed.(2) Cows, in spite of their greater weight, are more efficient than heifers, and animals milked thrice daily than those milked twice daily.(3) Within the breed there is a slight though definite tendency for gross efficiency to decrease with increase in live weight.(4) Greater than any of the foregoing differences in gross efficiency is that which exists within a breed due to differences in actual milk yield.(5) Stage of lactation has also much to do with gross efficiency. There is a steady decline in efficiency with advance in lactation from 38·75 to 29·25 per cent.

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Metabolic Power and Efficiency for an Amputee Cyclist: Implications for Cycling Technique

Journal of Applied Physiology ◽

10.1152/japplphysiol.00661.2020 ◽

2020 ◽

Author(s):

Steven J. Elmer ◽

James C. Martin

Keyword(s):

Scientific Evidence ◽

Mechanical Power ◽

Limb Amputation ◽

Sufficient Time ◽

Metabolic Power ◽

Gross Efficiency ◽

Leg Cycling ◽

Leg Flexion ◽

Delta Efficiency

Cycling technique is steeped in cultural lore. One deeply held belief is that "pulling-up" to lift the leg (increased muscular leg flexion) will optimize technique and improve efficiency. In contrast, scientific evidence suggests that when cyclists are instructed to pull-up efficiency decreases. However, such interventions may not have allowed sufficient time for cyclists to adapt and refine their technique. This case study documented how a cyclist with a complete unilateral limb amputation consumed metabolic power to produce mechanical power during single-leg cycling. The cyclist was a 4-time U.S. National Paralympic Champion who performed single-leg cycling for 7yrs and thus was fully adapted to pull-up. We hypothesized that a counterweight system, which reduced the requirement to pull-up, would decrease metabolic power and increase efficiency for this cyclist. The cyclist performed submaximal cycling (100, 135, 170, 205W, 80rpm, 5min) with and without a counterweight (10kg) on the unused crank. Expired gasses were measured, and metabolic power and gross efficiency were calculated. Metabolic power decreased on average by 87±7W (p<0.001) and gross efficiency increased from 16.3±1.9 to 18.0±1.8% (p<0.001) when cycling with the counterweight. During counterweighted single-leg cycling, the metabolic power of unloaded cycling decreased (317 vs. 238W) and delta efficiency was similar (25.2 vs. 25.5%). Results demonstrated that significant metabolic power was associated with pulling-up to produce muscular leg flexion power even in a cyclist who pulled-up substantially during cycling. Our findings confirm observations from previous studies that altered pedaling technique acutely and indicate that pulling-up during cycling is less efficient.

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Cycling Efficiency and Performance Following Short-Term Training Using Uncoupled Cranks

International Journal of Sports Physiology and Performance ◽

10.1123/ijspp.4.1.18 ◽

2009 ◽

Vol 4 (1) ◽

pp. 18-28 ◽

Cited By ~ 5

Author(s):

Andrew D. Williams ◽

Isaac Selva Raj ◽

Kristie L. Stucas ◽

James W. Fell ◽

Diana Dickenson ◽

...

Keyword(s):

Lactate Threshold ◽

Performance Enhancement ◽

Average Power ◽

Time Trial ◽

Mechanical Efficiency ◽

Cycling Performance ◽

Peak Power Output ◽

Gross Efficiency ◽

And Performance ◽

Study Participants

Objectives:Uncoupled cycling cranks are designed to remove the ability of one leg to assist the other during the cycling action. It has been suggested that training with this type of crank can increase mechanical efficiency. However, whether these improvements can confer performance enhancement in already well-trained cyclists has not been reported.Method:Fourteen well-trained cyclists (13 males, 1 female; 32.4 ± 8.8 y; 74.5 ± 10.3 kg; Vo2max 60.6 ± 5.5 mL·kg−1·min−1; mean ± SD) participated in this study. Participants were randomized to training on a stationary bicycle using either an uncoupled (n = 7) or traditional crank (n = 7) system. Training involved 1-h sessions, 3 days per week for 6 weeks, and at a heart rate equivalent to 70% of peak power output (PPO) substituted into the training schedule in place of other training. Vo2max, lactate threshold, gross efficiency, and cycling performance were measured before and following the training intervention. Pre- and post testing was conducted using traditional cranks.Results:No differences were observed between the groups for changes in Vo2max, lactate threshold, gross efficiency, or average power maintained during a 30-minute time trial.Conclusion:Our results indicate that 6 weeks (18 sessions) of training using an uncoupled crank system does not result in changes in any physiological or performance measures in well-trained cyclists.

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The effect of oestradiol-17 β implantation on the response in voluntary intake, live-weight gain and body composition, to fishmeal supplementation of silage offered to growing calves

The Journal of Agricultural Science ◽

10.1017/s0021859600064091 ◽

1987 ◽

Vol 108 (1) ◽

pp. 9-16 ◽

Cited By ~ 43

Author(s):

Margaret Gill ◽

D. E. Beever ◽

P. J. Buttery ◽

P. England ◽

M. J. Gibb ◽

...

Keyword(s):

Organic Matter ◽

Weight Gain ◽

Dry Matter ◽

Live Weight ◽

Energy Utilization ◽

Live Weight Gain ◽

Gross Efficiency ◽

Grass Silage ◽

Voluntary Intake

SummaryThe effect of oestradiol-17β on the response to fishmeal supplementation of grass silage was studied in young growing cattle. Voluntary intake and live-weight gain were recorded over 63 days with 36 British Friesian male castrates (initial live weight (LW) 119 kg) offered silage alone (C) or with 50 (FM1), 100 (FM2), or 150 (FM3) g fishmeal/kg silage dry matter. Twelve calves were allocated to each of treatments C and FM3 and six to treatments FM1 and FM2. Half of the calves on each treatment were ear-implanted with oestradiol-17β (Compudose 365) at the start of the experiment. The calves on treatments C and FM3 were slaughtered after 75 days and chemical analysis conducted on half of each carcass. The silage had an organic-matter digestibility in vivo of 0·794 and was well-fermented, with a pH of 3·7. Intake averaged 24·2±0·42 g D.M./kg LW over all the treatments and live-weight gain was 0·77 kg/day on the silage alone. There was a significant (P < 0·05) interaction between fishmeal and oestradiol-17β, such that response to the hormone was observed only in the presence of fishmeal at 100 or 150 g/kg silage D.M. A similar interaction was apparent between fishmeal at 150 g/kg silage D.M. and oestradiol-17β in the final weights of empty body and carcass. This level of fishmeal also increased protein gain from 96 to 147 g/day and this was further increased to 179 g/day in the implanted animals receiving fishmeal. However, the overall effect of oestradiol-17β on protein gain was not significant. Gross efficiency of energy utilization was significantly (P < 0·01) increased by fishmeal supplementation suggesting an improved balance of nutrients compared with the silage alone diet.

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Gross efficiency responses to exercise conditioning in adult males of various ages

Journal of Sports Sciences ◽

10.1080/02640419108729898 ◽

1991 ◽

Vol 9 (4) ◽

pp. 383-391 ◽

Cited By ~ 12

Author(s):

C. Gissane ◽

D.L. Corrigan ◽

J.A. White

Keyword(s):

Adult Males ◽

Gross Efficiency

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