Combining heat stress and moderate hypoxia reduces cycling time to exhaustion without modifying neuromuscular fatigue characteristics

Purpose: This study aimed to assess the requirement of protein in pre-exercise carbohydrate drinks for optimal endurance performance at high intensity and post-exercise fatigue recovery.Methods: Endurance performance at 85% V.⁢O2peak of young men (age 20 ± 0.9 years, V.⁢2peak 49.3 ± 0.3 L/min) was measured for two consecutive days using cycling time to exhaustion and total work exerted 2 h after three isocaloric supplementations: RICE (50 g, protein: 1.8 g), n = 7; SOY + RICE (50 g, protein: 4.8 g), n = 7; and WHEY + RICE (50 g, protein: 9.2 g), n = 7.Results: Endurance performance was similar for the three supplemented conditions. Nevertheless, maximal cycling time and total exerted work from Day 1 to Day 2 were improved in the WHEY + RICE (+21%, p = 0.05) and SOY-RICE (+16%, p = 0.10) supplemented conditions, not the RICE supplemented condition. Increases in plasma interleukin-6 (IL-6) were observed 1 h after exercise regardless of supplemented conditions. Plasma creatine kinase remained unchanged after exercise for all three supplemented conditions. Increases in ferric reducing antioxidant power (FRAP) after exercise were small and similar for the three supplemented conditions.Conclusion: Adding protein into carbohydrate drinks provides no immediate benefit in endurance performance and antioxidant capacity yet enhances fatigue recovery for the next day. Soy-containing carbohydrate drink, despite 50% less protein content, shows similar fatigue recovery efficacy to the whey protein-containing carbohydrate drink. These results suggest the importance of dietary nitrogen sources in fatigue recovery after exercise.

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Reproducibility of the Cycling Time to Exhaustion at in Highly Trained Cyclists

Canadian Journal of Applied Physiology ◽

10.1139/h03-046 ◽

2003 ◽

Vol 28 (4) ◽

pp. 605-615 ◽

Cited By ~ 8

Author(s):

Paul B. Laursen ◽

Cecilia M. Shing ◽

David G. Jenkins

Keyword(s):

Aerobic Power ◽

Cycling Performance ◽

Peak Oxygen Uptake ◽

Time To Exhaustion ◽

Subject Variability ◽

Progressive Exercise ◽

Two Measures ◽

The Mean ◽

Cycling Time ◽

Within Subject Variability

The purpose of the present study was to examine, in highly trained cyclists, the reproducibility of cycling time to exhaustion (Tmax) at the power output equal to that attained at peak oxygen uptake ([Formula: see text]) during a progressive exercise test. Forty-three highly trained male cyclists (M ± SD; age = 25 + 6 yrs; weight = 75 ± 7 kg; [Formula: see text] = 64.8 ± 5.2 mlùkg−1•min−1) performed two Tmax tests one week apart. While the two measures of Tmax were strongly related (r = 0.884; p < 0.001), Tmax from the second test (245 ± 57 s) was significantly higher than that of the first (237 ± 57 s; p = 0.047; two-tailed). Within-subject variability in the present study was calculated to be 6 ± 6%, which was lower than that previously reported for Tmax in sub-elite runners (25%). The mean Tmax was significantly (p < 0.05) related to both the second ventilatory turnpoint (VT2; r = 0.38) and to [Formula: see text] (r = 0.34). Despite a relatively low within-subject coefficient of variation, these data demonstrate that the second score in a series of two Tmax tests may be significantly greater than the first. Moreover, the present data show that Tmax in highly trained cyclists is moderately related to VT2 and [Formula: see text]Key words: maximal aerobic power, endurance, fatigue, anaerobic threshold, cycling performance

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Revealing Sex Differences During Upper and Lower Extremity Neuromuscular Fatigue in Older Adults Through a Neuroergonomics Approach

Frontiers in Neuroergonomics ◽

10.3389/fnrgo.2021.663368 ◽

2021 ◽

Vol 2 ◽

Author(s):

Ranjana K. Mehta ◽

Joohyun Rhee

Keyword(s):

Older Adults ◽

Sex Differences ◽

Lower Extremity ◽

Knee Extension ◽

Neuromuscular Fatigue ◽

Community Dwelling ◽

Knee Extensors ◽

Time To Exhaustion ◽

Functional Near Infrared Spectroscopy ◽

Over Time

Background: Sex differences in neuromuscular fatigue is well-documented, however the underlying mechanisms remain understudied, particularly for the aging population.Objective: This study investigated sex differences in fatigability of the upper and lower extremity of older adults using a neuroergonomics approach.Methods: Thirty community-dwelling older adults (65 years or older; 15 M, 15 F) performed intermittent submaximal fatiguing handgrip and knee extension exercises until voluntary exhaustion on separate days. Muscle activity from prime muscles of the hand/arm and knee extensors were monitored using electromyography, neural activity from the frontal, motor, and sensory areas were monitored using functional near infrared spectroscopy, and force output were obtained.Results: While older males were stronger than females across both muscle groups, they exhibited longer endurance times and greater strength loss during knee extension exercises. These lower extremity findings were associated with greater force complexity over time and concomitant increase in left motor and right sensory motor regions. While fatigability during handgrip exercises was comparable across sexes, older females exhibited concurrent increases in the activation of the ipsilateral motor regions over time.Discussion: We identified differences in the underlying central neural strategies adopted by males and females in maintaining downstream motor outputs during handgrip fatigue that were not evident with traditional ergonomics measures. Additionally, enhanced neural activation in males during knee exercises that accompanied longer time to exhaustion point to potential rehabilitation/exercise strategies to improve neuromotor outcomes in more fatigable older adults.

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