Effect of Cycling Cadence on Neuromuscular Function: A Systematic Review of Acute and Chronic Alterations

There is a wide range of cadence available to cyclists to produce power, yet they choose to pedal across a narrow one. While neuromuscular alterations during a pedaling bout at non-preferred cadences were previously reviewed, modifications subsequent to one fatiguing session or training intervention have not been focused on. We performed a systematic literature search of PubMed and Web of Science up to the end of 2020. Thirteen relevant articles were identified, among which eleven focused on fatigability and two on training intervention. Cadences were mainly defined as “low” and “high” compared with a range of freely chosen cadences for given power output. However, the heterogeneity of selected cadences, neuromuscular assessment methodology, and selected population makes the comparison between the studies complicated. Even though cycling at a high cadence and high intensity impaired more neuromuscular function and performance than low-cadence cycling, it remains unclear if cycling cadence plays a role in the onset of fatigue. Research concerning the effect of training at non-preferred cadences on neuromuscular adaptation allows us to encourage the use of various training stimuli but not to say whether a range of cadences favors subsequent neuromuscular performance.

Neuromuscular Adaptations after an Altitude Training Camp in Elite Judo Athletes

The aim of this study was to investigate neuromuscular adaptations in elite judo athletes after three weeks of power-oriented strength training at terrestrial altitude (2320 m). Nineteen men were assigned to altitude training (AL) (22.1 ± 2.3 years) and sea level training (SL) (22.6 ± 4.1 years). Neuromuscular assessment consisted of: (1) maximal isometric knee extensor (KE) torque, (2) KE rate of torque development (RTD), (3) quadriceps activity and voluntary activation, (4) soleus H-reflex, (5) quadriceps single (TTW) and double twitch torque (TDB100) and contraction time (CTTW). There were no significant differences between groups at baseline for any of the observed parameters. Significant differences were found between groups in terms of change in RTD (p = 0.04). Cohen’s d showed a positive significant effect (0.43) in the SL group and a negative significant effect (−0.58) in the AL group. The difference between groups in changes in CTTW as a function of altitude was on the edge of significance (p = 0.077). CTTW increased by 8.1 ± 9.0% in the AL group (p = 0.036) and remained statistically unchanged in the SL group. Only the AL group showed a relationship between changes in TTW and TDB100 and changes in RTD at posttest (p = 0.022 and p = 0.016, respectively). Altitude induced differences in muscular adaptations likely due to greater peripheral fatigue.

Advancements in the Protocol for Rate of Force Development/Relaxation Scaling Factor Evaluation

Brief submaximal actions are important for wide range of functional movements. Until now, rate of force development and relaxation scaling factor (RFD-SF and RFR-SF) have been used for neuromuscular assessment using 100–120 isometric pulses which requires a high level of attention from the participant and may be influenced by physiological and/or psychological fatigue. All previous studies have been conducted on a smaller number of participants which calls into question the eligibility of some of the outcome measures reported to date. Our aims were: (1) to find the smallest number of rapid isometric force pulses at different force amplitudes is still valid and reliable for RFD-SF slope (kRFD–SF) and RFR-SF slope (kRFR–SF) calculation, (2) to introduce a new outcome measure – theoretical peak of rate of force development/relaxation (TPRFD and TPRFR) and (3) to investigate differences and associations between kRFD–SF and kRFR–SF. A cross-sectional study was conducted on a group of young healthy participants; 40 in the reliability study and 336 in the comparison/association study. We investigated the smallest number of rapid isometric pulses for knee extensors that still provides excellent reliability of the calculated kRFD–SF and kRFR–SF (ICC2,1 ≥ 0.95, CV < 5%). Our results showed excellent reliability of the reduced protocol when 36 pulses (nine for each of the four intensity ranges) were used for the calculations of kRFD–SF and kRFR–SF. We confirmed the negligibility of the y-intercepts and confirmed the reliability of the newly introduced TPRFD and TPRFR. Large negative associations were found between kRFD–SF and kRFR–SF (r = 0.502, p < 0.001), while comparison of the absolute values showed a significantly higher kRFD–SF (8.86 ± 1.0/s) compared to kRFR–SF (8.03 ± 1.3/s) (p < 0.001). The advantage of the reduced protocol (4 intensities × 9 pulses = 36 pulses) is the shorter assessment time and the reduction of possible influence of fatigue. In addition, the introduction of TPRFD and TPRFR as an outcome measure provides valuable information about the participant’s maximal theoretical RFD/RFR capacity. This can be useful for the assessment of maximal capacity in people with various impairments or pain problems.

Exercise-Induced Fatigue in One Leg Does Not Impair the Neuromuscular Performance in the Contralateral Leg but Improves the Excitability of the Ipsilateral Corticospinal Pathway

To investigate the influence of pre-induced fatigue in one leg on neuromuscular performance and corticospinal responses of the contralateral homologous muscles, three experiments were conducted with different exercise protocols; A (n = 12): a 60 s rest vs. time-matched sustained left leg knee extension maximum voluntary contraction (MVC), B (n = 12): a 60 s rest vs. time-matched left leg MVC immediately followed by 60 s right leg MVC, and C (n = 9): a similar protocol to experiment B, but with blood flow occluded in the left leg while the right leg was performing the 60 s MVC. The neuromuscular assessment included 5 s knee extensions at 100%, 75%, and 50% of MVC. At each force level, transcranial magnetic and peripheral nerve stimuli were elicited to investigate the influence of different protocols on the right (tested) knee extensors’ maximal force output, voluntary activation, corticospinal excitability, and inhibition. The pre-induced fatigue in the left leg did not alter the performance nor the neuromuscular responses recorded from the right leg in the three experiments (all p > 0.3). However, enhanced corticospinal pathway excitability was evident in the tested knee extensors (p = 0.002). These results suggest that the pre-induced fatigue and muscle ischemia in one leg did not compromise the central and peripheral components of the neuromuscular function in the tested contralateral leg.

SYMMETRIC-ELECTROMYOGRAPHIC ANALYSIS IN THE EVALUATION OF SCOLIOSIS TREATMENT

ABSTRACT Introduction: Scoliosis is a three-dimensional deformity of the spine, characterized by a lateral shift that affects body posture. The Pilates Method (PM) promotes alterations in the biomechanics and neuromuscular activation pattern. Objective: The aim of this study was to analyze electromyography (EMG) and symmetrography (SMTG) technologies applied in the evaluation of neuromuscular and postural effects on right convex thoracolumbar scoliosis (RCTS) after applying a PM therapeutic protocol. Methods: This is an exploratory study of 5 male and female adolescents, with an average age of 14.4 years. The subjects underwent postural asymmetry assessments through SMTG and neuromuscular assessment through surface EMG of the trapezius (TRAP), erector spinae (ERE), oblique (OBLI) and rectus abdominis (RA) muscles. The electromyographic signals were processed in the temporal (EMGAmp) and spectral (EMGFmed) domains. The therapeutic protocol consisted of 24 sessions of Pilates floor exercises held twice a week with a duration of 45 minutes. Results: There was an improvement in scoliosis and asymmetric shoulders in one subject (20%) and in three other subjects with hip asymmetry. There was an improvement in one subject (33.33%), as demonstrated by SMTG. EMGAmp measurements demonstrated a significant difference between before and after (p≈0) and among the muscles (p≈0). EMGFmed measurements demonstrated that there was only a difference between before and after (p≈0). It was verified that the most noteworthy muscles in terms of EMGAmp were TRAP and ERE, emphasizing the existence of an increase in the mean EMGAmp for ERE. Muscle behavior for measurements in EMGFmed demonstrated a higher mean increase for RA and OBLI muscles. Conclusion: It is concluded that the EMG and SMTG technologies are important tests for monitoring the progress of scoliosis and in treatment decisions. Level of Evidence III; Diagnostic Studies - Investigating diagnostic tests.

Improving the measurement of TMS-assessed voluntary activation in the knee extensors

The present study was designed to test the accuracy, validity, reliability and sensitivity of the main outcomes of alternative methods for the measure of TMS-assessed voluntary activation (VATMS) in the knee extensors. Ten healthy recreationally active males (24 ± 5 years) completed a neuromuscular assessment protocol (NMA) before and immediately after a fatiguing isometric exercise, consisting of two sets of five contractions (50%, 62.5%, 75%, 87.5%, and 100% of Maximal Voluntary Contraction; MVC) with superimposed TMS-evoked twitches (SITs) for calculation of VATMS (1x5C vs. 2x5C). The protocol was performed on two separate occasions for the measurement of between-day reliability. Where deemed appropriate, comparisons were made with a routinely used protocol [i.e. 50%, 75%, and 100% of MVC (1x3C) performed three times (3x3C)] from re-analysed data (Dekerle et al., 2018). Confidence intervals for the measure of a key determinant of VATMS (estimated resting twitch) were similar between 1x5C and 2x5C but improved by six-fold when compared to 1x3C (P<0.05). Potentiated twitch force evoked via percutaneous electrical stimulation of the femoral nerve was unchanged from pre- to post-NMA at baseline for 1x5C (P>0.05) but decreased for 2x5C and 3x3C (P<0.05). Its recovery post-exercise was lesser for 1x5C compared to 2x5C and 3x3C (P<0.05), with no difference between the latter two (P>0.05). Absolute reliability was strong enough for both 1x5C and 2x5C to depict a true detectable change in the sample’s VATMS following the fatiguing exercise (TEM < 3% at rest, <9% post-exercise) but 2x5C was marginally more sensitive to individual’s changes at baseline. In conclusion, both 1x5C and 2x5C provide reliable measures of VATMS. However, the 1x5C protocol may hold stronger internal validity.