Effects of acute and multi-day low-dose sodium bicarbonate intake on high-intensity endurance exercise performance in male recreational cyclists

PURPOSE

This study aimed to compare the effects of acute and multi-day low-dose sodium bicarbonate (SB) intake on high-intensity endurance exercise performance.

METHODS

In a randomized, double-blind, cross-over design, twelve recreational male cyclists (age: 31.17 ± 4.91 years; V ˙ O2peak: 47.98 ± 7.68 ml·kg-1·min-1) completed three endurance performance tests following acute SB (ASB, 0.2 g·kg-1 SB), multi-day SB (MSB, 0.2 g·kg-1·day-1 SB for four days), and placebo (PLA) intake. The high-intensity endurance performance was assessed with a cycling exercise test, wherein participants cycled on a bicycle ergometer at 95% of the predetermined anaerobic threshold for 30 min, followed by a time-to-exhaustion test at 110% of the anaerobic threshold. Data were analyzed using one-way and two-way repeated-measures ANOVA.

RESULTS

Significant main effects of supplementation protocol were evident in pre-exercise bicarbonate concentrations (F = 27.93; p < 0.01; partial eta squared (η2) = 0.72; false discovery rate (FDR)-adjusted p value = 0.001). Prior to performance test, blood bicarbonate concentrations were significantly higher in MSB (25.78 ± 1.63 mmol·L-1 [95% CI 26.55-28.44] (p < 0.001; FDR-adjusted p value = 0.001)) and ASB (27.49 ± 1.49 mmol·L-1 [95% CI 24.75-26.81] (p < 0.001; FDR-adjusted p value = 0.007)) compared to PLA (23.75 ± 1.40 mmol·L-1 [95% CI 22.86 to 24.64]). Time-to-exhaustion increased in MSB (54.27 ± 9.20 min [95% CI 48.43-60.12]) compared to PLA (49.75 ± 10.80 min [95% CI 42.89-56.62]) (p = 0.048); however, this increase in MSB did not reach the significance threshold of 1% FDR (FDR-adjusted p value = 0.040). No significant difference was noted in exhaustion times between ASB (51.15 ± 8.39 min [95% CI 45.82-56.48]) and PLA (p > 0.05).

CONCLUSION

Both acute and multi-day administration of low-dose SB improves buffering system in cyclists; nevertheless, neither intervention demonstrates sufficient efficacy in enhancing high-intensity endurance performance.

β-Alanine supplementation increased physical performance and improved executive function following endurance exercise in middle aged individuals

Background

Sarcopenia, a reduction in muscle mass and function seen in aging populations, may be countered by improving systemic carnosine stores via beta-Alanine (β-alanine) supplementation. Increasing systemic carnosine levels may result in enhanced anti-oxidant, neuro-protective and pH buffering capabilities. This enhancement should result in improved exercise capacity and executive function.

Methods

Twelve healthy adults (average age = 60.5 ± 8.6 yrs, weight = 81.5 ± 12.6 kg) were randomized and given either 2.4 g/d of β-alanine (BA) or Placebo (PL) for 28 days. Exercise capacity was tested via bouts on a cycle ergometer at 70% VO₂ peak. Executive function was measured by Stroop Tests 5 min before exercise (T1), immediately before exercise (T2), immediately following fatigue (T3), and 5 min after fatigue (T4). Lactate measures were taken pre/post exercise. Heart rate, Rating of Perceived Exertion (RPE) and VO₂ were recorded throughout exercise testing.

Results

PRE average time-to-exhaustion (TTE) for the PL and BA group were not significantly different (Mean ± SD; 9.4 ± 1.4mins vs 11.1 ± 2.4mins, respectively, P = 0.7). POST BA supplemented subjects cycled significantly longer than PRE (14.6 ± 3.8mins vs 11.1 ± 2.4mins, respectively, P = 0.04) while those given PL did not (8.7 ± 2.4mins vs 9.4 ± 1.4mins, respectively, P = 0.7). PL subjects were slower in completing the Stroop test POST at T4 compared to T3 (T3 = − 13.3 ± 8.6% vs T4 = 2.1 ± 8.3%, P = 0.04), while the BA group (T3 = − 9.2 ± 6.4% vs T4 = − 2.5 ± 3.5%, P = 0.5) was not. POST lactate production expressed a trend when comparing treatments, as the BA group produced 2.4 ± 2.6 mmol/L more lactate than the PL group (P = 0.06). Within group lactate production for BA (P = 0.4) and PL (P = 0.5), RPE (P = 0.9) and heart rate (P = 0.7) did not differ with supplementation.

Conclusion

BA supplementation increased exercise capacity and eliminated endurance exercise induced declines in executive function seen after recovery. Increased POST TTE coupled with similar PRE vs POST lactate production indicates an improvement in the ability of BA to extend exercise durations. Furthermore, by countering endurance exercise’s accompanying deficits in executive function, the aging population can maintain benefits from exercise with improved safety.

Critical power: How different protocols and models affect its determination

In cycling, critical power (CP) and work above CP (W') can be estimated through linear and nonlinear models. Despite the concept of CP representing the upper boundary of sustainable exercise, overestimations may be made as the models possess inherent limitations and the protocol design is not always appropriate.

OBJECTIVES

To measure and compare CP and W' through the exponential (CP_exp), 3-parameter hyperbolic (CP_3-hyp), 2-parameter hyperbolic (CP_2-hyp), linear (CP_linear), and linear 1/time (CP_1/time) models, using different combinations of TTE trials of different durations (approximately 1-20min).

DESIGN

Repeated measures.

METHODS

Thirteen healthy young cyclists (26±3years; 69.0±9.2kg; 174±10cm; 60.4±5.9mLkg^-1min^-1) performed five TTE trials on separate days. CP and W' were modeled using two, three, four, and/or five trials. All models were compared against a criterion method (CP_3-hyp with five trials; confirmed using the leaving-one-out cross-validation analysis) using smallest worthwhile change (SWC) and concordance correlation coefficient (CCC) analyses.

RESULTS

CP was considerably overestimated when only trials lasting less than 10min were included, independent of the mathematical model used. Following CCC analysis, a number of alternative methods were able to predict our criterion method with almost a perfect agreement. However, the application of other common approaches resulted in an overestimation of CP and underestimation of W', typically these methods only included TTE trials lasting less than 12min.

CONCLUSIONS

Estimations from CP_3-hyp were found to be the most accurate, independently of TTE range. Models that include two trials between 12 and 20min provide good agreement with the criterion method (for both CP and W').

Low-level laser therapy improves the VO2 kinetics in competitive cyclists

Some evidence supports that low-level laser therapy (LLLT) reduces neuromuscular fatigue, so incrementing sports performance. A previous randomized controlled trial of our group showed increased exercise tolerance in male competitive cyclists treated with three different LLLT doses (3, 6, and 9 J/diode; or 135, 270, and 405 J/thigh) before time-to-exhaustion cycling tests. Now, the present study was designed to evaluate the effects of these LLLT doses on the VO₂ kinetics of athletes during cycling tests. Twenty male competitive cyclists (29 years) participated in a crossover, randomized, double-blind, and placebo-controlled trial. On the first day, the participants performed an incremental cycling test to exhaustion to determine maximal oxygen uptake (VO_2MAX) and maximal power output (PO_MAX), as well as a familiarization with the time-to-exhaustion test. In the following days (2 to 5), all participants performed time-to-exhaustion tests at PO_MAX. Before the exhaustion test, different doses of LLLT (3, 6, and 9 J/diode; or 135, 270, and 405 J/thigh, respectively) or placebo were applied bilaterally to the quadriceps muscle. All exhaustion tests were monitored online by an open-circuit spirometry system in order to analyze the VO₂ amplitude, VO₂ delay time, time constant (tau), and O₂ deficit. Tau and O₂ deficit were decreased with LLLT applications compared to the placebo condition (p < 0.05). No differences (p > 0.05) were found between the experimental conditions for VO₂ amplitude and VO₂ delay time. In conclusion, LLLT decreases tau and O₂ deficit during time-to-exhaustion tests in competitive cyclists, and these changes in VO₂ kinetics response can be one of the possible mechanisms to explain the ergogenic effect induced by LLLT.

The effect of mental fatigue on critical power during cycling exercise

PURPOSE

Time to exhaustion (TTE) tests used in the determination of critical power (CP) and curvature constant (W') of the power-duration relationship are strongly influenced by the perception of effort (PE). This study aimed to investigate whether manipulation of the PE alters the CP and W'.

METHODS

Eleven trained cyclists completed a series of TTE tests to establish CP and W' under two conditions, following a mentally fatiguing (MF), or a control (CON) task. Both cognitive tasks lasted 30 min followed by a TTE test. Ratings of PE and heart rate (HR) were measured during each TTE. Blood lactate was taken pre and post each TTE test. Ratings of perceived mental and physical fatigue were taken pre- and post-cognitive task, and following each TTE test.

RESULTS

Perceived MF significantly increased as a result of the MF task compared to baseline and the CON task (P < 0.05), without a change in perceived physical fatigue (P > 0.05). PE was significantly higher during TTE in the MF condition (P < 0.05). Pre-post blood lactate accumulation was significantly lower after each TTE in MF condition (P < 0.05). HR was not significant different between conditions (P > 0.05). Neither cognitive task induced any change in CP (MF 253 ± 51 vs. CON 247 ± 58W; P > 0.05), although W' was significantly reduced in the MF condition (MF 22.8 ± 4.5 vs. CON 29.3 ± 6.3 kJ; P < 0.01).

CONCLUSION

MF has no effect of CP, but reduces the W' in trained cyclists. Lower lactate accumulation during TTE tests following MF suggests that cyclists were not able to fully expend W' even though they exercised to volitional exhaustion.