Muscle fibre conduction velocity and cardiorespiratory response during incremental cycling exercise in young and older individuals with different training status

Photobiomodulation does not improve anaerobic performance in well-trained cyclists

To determine if photobiomodulation (PBM) has ergogenic effects on the anaerobic performance of well-trained cyclists. Fifteen healthy male road or mountain bike cyclists participated in this randomized, double-blinded, placebo-controlled, crossover study. Athletes were randomly assigned to receive photobiomodulation (630 nm, 4.6 J/cm², 6 J per point, 16 points, PBM session) or placebo intervention (PLA session) in the first session. The athletes then performed a 30-s Wingate test to determine mean and peak average power, relative power, mean and peak velocity, mean and peak RPM, fatigue index, total distance, time to peak power, explosive strength, and power drop. After 48 h, athletes returned to the laboratory for the crossover intervention. The repeated-measures ANOVA test followed by Bonferroni post hoc test or Friedman test with Dunn's post hoc test (p < 0.05), and Cohen's d statistic were used for comparisons. Performance in the Wingate test was not significantly different (p > 0.05) between PBM and PLA sessions for any variable. Only a small effect size was detected for time to peak power (-0.40; 1.11 to 0.31) and explosive strength (0.38; -0.34 to 1.09). We conclude that irradiation with red light, under a low energy density, does not promote ergogenic effects on the anaerobic performance of cycling athletes.

Impact of Power Output on Muscle Activation and 3D Kinematics During an Incremental Test to Exhaustion in Professional Cyclists

This study aimed to quantify the influence of an increase in power output (PO) on joint kinematics and electromyographic (EMG) activity during an incremental test to exhaustion for a population of professional cyclists. The hip flexion/extension and internal/external rotation as well as knee abduction/adduction ranges of motion were significantly decreased at 100% of the maximal aerobic power (MAP). EMG analysis revealed a significant increase in the root mean square (RMS) for all muscles from 70% of the MAP. Gastrocnemius muscles [lateralis gastrocnemius (GasL) and medialis gastrocnemius (GasM)] were the less affected by the increase of PO. Cross-correlation method showed a significant increase in the lag angle values for VM in the last stage compared to the first stage, meaning that the onset of the activation started earlier during the pedaling cycle. Statistical Parametric Mapping (SPM) demonstrated that from 70% MAP, biceps femoris (BF), tibialis anterior (TA), gluteus maximus (GM), and rectus femoris (RF) yielded larger ranges of the crank cycle on which the level of recruitment was significantly increased. This study revealed specific muscular and kinematic coordination for professional cyclists in response to PO increase.

Evaluation of the Electromyography Test for the Analysis of the Aerobic-Anaerobic Transition in Elite Cyclists during Incremental Exercise

(1) Background: The aim of this study was to investigate the validity and reliability of surface electromyography (EMG) for automatic detection of the aerobic and anaerobic thresholds during an incremental continuous cycling test using 1 min exercise periods in elite cyclists. (2) Methods: Sixteen well-trained cyclists completed an incremental exercise test (25 W/1 min) to exhaustion. Surface bipolar EMG signals were recorded from the vastus lateralis, vastus medialis, biceps femoris, and gluteus maximus, and the root mean square (RMS) were assessed. The multi-segment linear regression method was used to calculate the first and second EMG thresholds (EMGT1 and EMGT2). During the test, gas exchange data were collected to determine the first and second ventilatory thresholds (VT1 and VT2). (3) Results: Two breakpoints (thresholds) were identified in the RMS EMG vs. time curve for all muscles in 75% of participants. The two breakpoints, EMGT1 and EMGT2, were detected at around 70%–80% and 90%–95% of VO2MAX, respectively. No significant differences were found between the means of VT1 and EMGT1 for the vastii and biceps femoris muscles (p > 0.05). There were no significant differences between means of EMGT2 and VT2 (p > 0.05). (4) Conclusions: It is concluded that the multi-segment linear regression algorithm is a valid non-invasive method for analyzing the aerobic-anaerobic transition during incremental tests with 1 min stage durations.

The temporal relationship of thresholds between muscle activity and ventilation during bicycle ramp exercise in community dwelling elderly males

[Purpose] To compare the appearance time of the ventilatory threshold point and the electromyographic threshold in the activity of the vastus lateralis, rectus femoris, biceps femoris long head and gastrocnemius lateral head muscles during ramp cycling exercise in elderly males. [Subjects and Methods] Eleven community dwelling elderly males participated in this study. Subjects performed exercise testing with an expiratory gas analyzer and surface electromyography to evaluate the tested muscle activities during ramp exercise. [Results] The electromyographic threshold for rectus femoris was not valid because the slope after electromyographic threshold was not significant as compared to that before electromyographic threshold. The slope of the regression line for vastus lateralis was significantly decreased after electromyographic threshold while biceps femoris and gastrocnemius were increased. The electromyographic threshold appearance times for vastus lateralis and gastrocnemius were significantly earlier than ventilatory threshold point. There were no difference in electromyographic threshold appearance times among three muscles. [Conclusion] These results suggest that the increase in the slope of the regression line after electromyographic threshold for vastus lateralis was decreased, possibly indicating to postpone muscular fatigue resulting from the activation of biceps femoris and gastrocnemius as biarticular antagonists. This recruitment pattern might be an elderly-specific strategy.

Detecting fatigue thresholds from electromyographic signals: A systematic review on approaches and methodologies

The aim of the current paper was to systematically review the relevant existing electromyographic threshold concepts within the literature. The electronic databases MEDLINE and SCOPUS were screened for papers published between January 1980 and April 2015 including the keywords: neuromuscular fatigue threshold, anaerobic threshold, electromyographic threshold, muscular fatigue, aerobic-anaerobictransition, ventilatory threshold, exercise testing, and cycle-ergometer. 32 articles were assessed with regard to their electromyographic methodologies, description of results, statistical analysis and test protocols. Only one article was of very good quality. 21 were of good quality and two articles were of very low quality. The review process revealed that: (i) there is consistent evidence of one or two non-linear increases of EMG that might reflect the additional recruitment of motor units (MU) or different fiber types during fatiguing cycle ergometer exercise, (ii) most studies reported no statistically significant difference between electromyographic and metabolic thresholds, (iii) one minute protocols with increments between 10 and 25W appear most appropriate to detect muscular threshold, (iv) threshold detection from the vastus medialis, vastus lateralis, and rectus femoris is recommended, and (v) there is a great variety in study protocols, measurement techniques, and data processing. Therefore, we recommend further research and standardization in the detection of EMGTs.

Upper limb aerobic training improves aerobic fitness and all-out performance of America's Cup grinders

This research on "America's Cup" grinders investigated the effects of a specific eight-week long-arm cranking ergometer (ACE) training on upper body (UB) aerobic fitness (ventilatory threshold - Tvent, respiratory compensation point- RCP, -oxygen uptake peak - VO₂peak) and high intensity working capacity. The training consisted of sessions carried out for 20-30 mins, three times per week, at an intensity between the UB-Tvent and UB-RCP, and replaced part of a typical lower limb aerobic training whilst maintaining the usual weekly schedule of callisthenics, resistance training and sailing. Seven sailors, including four grinders and three mastmen (age 30 ± 5.5 years, height 1.9 ± 0.04 m, body mass 102 ± 3.6 kg), were evaluated through both an ACE cardiopulmonary maximal exercise test (CPET) and an ACE all-out up to exhaustion exercise test, before and after the ACE training. UB aerobic fitness improved significantly: UB-VO₂peak increased from 4.29 ± 0.442 to 4.52 ± 0.522 l·min(-1) (6.4 ± 3.66%), VO₂ at UB-Tvent from 2.42 ± 0.282 to 2.97 ± 0.328 l·min(-1) (22.8 ± 5.09%) and VO₂ at UB-RCP from 3.25 ± 0.402 to 3.75 ± 0.352 l·min(-1) (16.1 ± 10.83%). Peak power at the ACE CPET increased from 351 ± 27.5 to 387 ± 33.5 W (10.5 ± 6.93%). The all-out test total mechanical work increased from 28.9 ± 2.35 to 40.1 ± 3.76 kJ (72.1 ± 4.67%). In conclusion, a high intensity aerobic ACE training can be effective in improving grinding performance by increasing UB aerobic fitness and all-out working capacity.

Enhancing cognitive functioning in the elderly: multicomponent vs resistance training

PURPOSE

The primary purpose of this study was to compare the effects of two different exercise training programs on executive cognitive functions and functional mobility in older adults. A secondary purpose was to explore the potential mediators of training effects on executive function and functional mobility with particular reference to physical fitness gains.

METHODS

A sample of 42 healthy community dwelling adults aged 65 to 75 years participated twice weekly for 3 months in either: (1) multicomponent training, prioritizing neuromuscular coordination, balance, agility, and cognitive executive control; or (2) progressive resistance training for strength conditioning. Participants were tested at baseline (T(1)), following a 4-week control period (T(2)), and finally at postintervention (T(3)) for executive function (inhibition and cognitive flexibility) and functional mobility (maximal walking speed with and without additional task requirements). Cardiorespiratory and muscular fitness were also assessed as potential mediators.

RESULTS

Indices of inhibition, the functions involved in the deliberate withholding of prepotent or automatic responses, and measures of functional mobility improved after the intervention, independent of training type. Mediation analysis suggested that different mechanisms underlie the effects of multicomponent and progressive resistance training. While multicomponent training seemed to directly affect inhibitory capacity, resistance training seemed to affect it indirectly through gains in muscular strength. Physical fitness and executive function variables did not mediate functional mobility changes.

CONCLUSION

These results confirm that physical training benefits executive function and suggest that different training types might lead to such benefits through different pathways. Both types of training also promoted functional mobility in older adulthood; however, neither inhibitory capacity, nor muscular strength gains seemed to explain functional mobility outcomes.

Resposta da cinética de consumo de oxigênio e da eficiência mecânica delta de homens e mulheres em diferentes intensidades de esforço

INTRODUÇÃO:A eficiência mecânica delta (EMΔ ) e a cinética do consumo de oxigênio (K<img src="/img/revistas/rbme/v17n4/a13cr01.jpg" align="absmiddle" />2) são influenciadas por parâmetros metabólicos musculares e pelo transporte de <img src="/img/revistas/rbme/v17n4/a13cr01.jpg" align="absmiddle" />2. O objetivo do presente estudo foi determinar a diferença na K<img src="/img/revistas/rbme/v17n4/a13cr01.jpg" align="absmiddle" />2 e na EMΔ em três intensidades de esforço nos dois gêneros. MÉTODOS: 56 sujeitos (26 mulheres) foram submetidos ao protocolo de esforço escalonado, contínuo e máximo (GxT) no cicloergômetro mecânico para determinação da potência aeróbia máxima (<img src="/img/revistas/rbme/v17n4/a13cr01.jpg" align="absmiddle" />2máx), carga máxima (Wmax), limiar anaeróbio (AT) e ponto de compensação respiratória (PCR). O AT foi determinado através dos métodos V-slope e E <img src="/img/revistas/rbme/v17n4/a13cr02.jpg" align="absmiddle" /><img src="/img/revistas/rbme/v17n4/a13cr02.jpg" align="absmiddle" />E / <img src="/img/revistas/rbme/v17n4/a13cr01.jpg" align="absmiddle" />2; o PCR através da relação <img src="/img/revistas/rbme/v17n4/a13cr01.jpg" align="absmiddle" />2 versus <img src="/img/revistas/rbme/v17n4/a13cr02.jpg" align="absmiddle" />E ; ambos por dois avaliadores. A EMΔ e a K <img src="/img/revistas/rbme/v17n4/a13cr01.jpg" align="absmiddle" />2 foram consideradas como a inclinação entre <img src="/img/revistas/rbme/v17n4/a13cr01.jpg" align="absmiddle" />2 versus Watts e <img src="/img/revistas/rbme/v17n4/a13cr01.jpg" align="absmiddle" />2 versus tempo (s), respectivamente, do começo do teste até o AT (S1), do AT ao PCR (S2) e do PCR ao <img src="/img/revistas/rbme/v17n4/a13cr01.jpg" align="absmiddle" />2máx (S3), determinada por análise de regressão linear. RESULTADOS: Para a EMΔ, diferenças significativas foram observadas entre S1 versus S2 (p = 0,001), S1 versus S3 (p = 0,001) e S2 versus S3 (p = 0,006). Não foi observada diferença (p = 0,060) ou interação significativa (p = 0,062) entre homens versus mulheres. Para a K <img src="/img/revistas/rbme/v17n4/a13cr01.jpg" align="absmiddle" />2 diferenças significativas foram observadas entre S1 versus S3 (p = 0,001) e S2 versus S3 (p = 0,001) em ambos gêneros. Diferenças (p = 0,001) e interação significativa (p = 0,006) foram observadas entre homens versus mulheres, no último parâmetro. CONCLUSÕES: A EMΔ decresce com o incremento da intensidade de trabalho, porém, não há diferenças quando se compara homens e mulheres. Por outro lado, as mulheres apresentam K <img src="/img/revistas/rbme/v17n4/a13cr01.jpg" align="absmiddle" />2 mais rápida do que os homens.