Revisiting the Single-Visit Protocol for Determining the Electromyographic Fatigue Threshold

Caffeine Expectancy Does Not Influence the Physical Working Capacity at the Fatigue Threshold

ABSTRACT

Ambrozy, CA, Hawes, NE, Hayden, OL, Sortzi, I, and Malek, MH. Caffeine expectancy does not influence the physical working capacity at the fatigue threshold. J Strength Cond Res 38(6): 1056-1062, 2024-The placebo effect occurs when a desired outcome is experienced due to the belief that a treatment is effective, even in the absence of an active ingredient. One explanation for this effect is based on a person's expectations of a drug or supplement. Although caffeine's effects on sports performance have been studied, little is known about how expectations of caffeine affect neuromuscular fatigue during continuous muscle action. The physical working capacity at the fatigue threshold (PWCFT) can be used to assess neuromuscular fatigue noninvasively using surface electromyography. Thus, the purpose of this study was to investigate whether caffeine expectancy influences PWCFT. We hypothesized that regardless of expectancy, caffeine consumption would delay neuromuscular fatigue. The study involved 8 healthy college-aged men (mean ± SEM: age, 25.6 ± 1.0 years) who visited the laboratory on 4 occasions, each separated by 7 days. The subjects completed 4 experimental conditions, in random order, where they were told that they were consuming caffeine or placebo and either received caffeine or placebo. After consuming the drink, the subjects remained in the laboratory for an hour and then performed an incremental exercise test. The results showed that the condition where subjects were told that they were consuming caffeine and received caffeine had significantly higher mean values for maximal power output (F(3, 21) = 11.75; p < 0.001), PWCFT (F(3, 21) = 12.28; p < 0.001), PWCFT (%maximal power output; F(3, 21) = 8.75; p < 0.001), and heart rate at end exercise (%predicted; F(3, 21) = 3.83; p = 0.025) compared with the 2 conditions where placebo was received. However, no statistically significant mean differences were found from the condition where subjects were told that they were consuming placebo but consuming caffeine. This suggests that a person's expectancy and potential somatic response may serve as a cue for how an ergogenic aid or placebo could affect subsequent performance.

The Influence of Cold Therapy on the Physical Working Capacity at the Electromyographic Threshold for Consecutive Exercise Sessions

BACKGROUND

The purpose of this study was to determine whether cold therapy after the first exercise test influences the physical working capacity at the fatigue threshold (PWCFT) during the second exercise test. We hypothesized that cold therapy would delay the onset of PWCFT for the second exercise test relative to the control visit (i.e., no cold therapy).

METHODS

Eight healthy college-aged men volunteered for the present study. For each of the two visits, subjects performed incremental, single-leg, knee-extensor ergometer, followed by either resting for 30 min (control visit) or having a cold pack applied for 15 min and then resting for 15 min (experimental visit). Then, the same exercise test was performed. The order of visits (control vs. experimental) was randomized for each subject. The exercise indices and PWCFT were determined for each of the two visits and statistically analyzed using two-way repeated measures analysis of variance.

RESULTS

The results indicate no significant (p > 0.05) mean differences for maximal power output, heart rate at end-exercise, and PWCFT between the control and cold therapy visits. Moreover, there were no significant (p > 0.05) mean differences between the first and second exercise workbout within each visit.

CONCLUSIONS

The findings of this study suggest that cold therapy did not influence neuromuscular fatigue.

Listening to Music Pretask on Neuromuscular Fatigue During Exercise: Preferred vs. Nonpreferred Music

ABSTRACT

Diehl, TL, Yu, JN, Storer, FM, and Malek, MH. Listening to music pretask on neuromuscular fatigue during exercise: preferred vs. nonpreferred music. J Strength Cond Res 37(7): 1537-1542, 2023-Studies indicate that listening to music can elicit various physiological responses ranging from distracting the subject from the sensation of fatigue to changes in specific regions of the brain. Indeed, the use of music, as an ergogenic aid, to improve human performance has been shown to be a powerful tool. Many studies on the effect of music on human performance have had subjects listen to music in-task (i.e., during the activity). There is, however, a growing interest to determine the role of listening to music pretask (i.e., before the activity) on exercise outcomes. In addition, it is important to consider the subject's music preference as that may influence the target outcome variable(s). Therefore, the purpose of this study was to determine whether listening to preferred music pretask influences the physical working capacity at the fatigue threshold (PWC FT ). We hypothesized that listening to preferred music pretask will increase the estimated PWC FT compared with the control condition, which is listening to nonpreferred music. Nine healthy college-aged men (mean ± SEM : age, 23.4 ± 0.4 years; body mass, 71.6 ± 2.5 kg; and height, 1.81 ± 0.02 m) volunteered for this study. Each subject visited the laboratory on 2 occasions separated by 7 days. In a randomized manner, subjects listened to their preferred music for 30 minutes before the exercise test for 1 visit, whereas for the other visit, subjects listened to their nonpreferred music 30 minutes before the exercise test. Exercise outcomes were recorded for both visits and analyzed using a paired-samples t test. The results indicated no significant ( p > 0.05) mean differences for maximal power output (mean ± SEM : 60 ± 4 W vs. 60 ± 4 W), PWC FT (25 ± 3 W vs. 29 ± 2 W), or heart rate at end exercise (153 ± 8 b·min -1 vs. 155 ± 7 b·min -1 ) between listening to nonpreferred vs. preferred music 30 minutes before the exercise activity. These findings suggest that listening to music pretask does not influence neuromuscular fatigue during the exercise workbout.

Perceived Consumption of a High-Dose Caffeine Drink Delays Neuromuscular Fatigue

ABSTRACT

Elhaj, HM, Imam, O, Page, BW, Vitale, JM, and Malek, MH. Perceived consumption of a high-dose caffeine drink delays neuromuscular fatigue. J Strength Cond Res 36(5): 1185-1190, 2022-The placebo effect is a concept in which a desired outcome arises, mainly from the belief that the treatment (i.e., supplement or drug) was beneficial although no active ingredient was given. The results of studies related to the placebo effect primarily examine functional performance. What remains unanswered, however, is whether these changes in performance are associated with neuromuscular alterations in the exercised muscles. The purpose of the study, therefore, was to determine the influence of the placebo effect on the physical working capacity fatigue threshold (PWCFT) for a continuous exercise paradigm. To achieve this aim, subjects were told that they were participating in a study to determine the dosage response (low or high) of caffeine on neuromuscular fatigue when in fact no caffeine was given during the experiment. We hypothesized that the perceived consumption of the high-dose caffeine drink would result in a higher PWCFT than the perceived consumption of the low-dose caffeine drink and placebo. Secondarily, we hypothesized that the perceived consumption of the high-dose caffeine drink would result in a higher power output than the perceived consumption of the placebo. Nine healthy college-aged men (mean ± SEM: age, 25.7 ± 1.3 years; body mass, 84.4 ± 3.1 kg; and height: 1.82 ± 0.02 m) volunteered to be in the study. For each of the visits, subjects were given an 8 oz. bottle of water with dissolved crystal light. After the drink was consumed, subjects rested in the laboratory for 1 hour before performing the incremental single-leg knee-extensor ergometry. Immediately after the termination of the incremental single-leg knee-extensor ergometry, the subject was asked which caffeine dose (placebo, low, or high) they believed they consumed for that visit. There were no significant mean differences for maximal power output for the 3 perceived conditions (placebo: 62 ± 3, low-dose caffeine: 62 ± 4, and high-dose caffeine: 65 ± 3 W). When the subjects perceived consuming the high-dose caffeine drink, there were significant mean differences (all p-values < 0.01), for PWCFT, between the other conditions (mean ± SEM: placebo: 23 ± 3 W, low-dose caffeine: 26 ± 2 W, and high-dose caffeine: 42 ± 3 W). This corresponded to a significant mean difference (all p-values < 0.01) when the PWCFT was presented as a percentage of the maximal power output (mean ± SEM: placebo: 37 ± 5%, low-dose caffeine: 42 ± 3%, and high-dose caffeine: 64 ± 3%). The application of our results may indicate that the subject's expectancy, to caffeine consumption, plays a critical role in delaying the onset of neuromuscular fatigue despite not receiving any caffeine in their drinks.

The Evolution of the Physical Work Capacity at the Fatigue Threshold Test: Past, Present, and Future

ABSTRACT

Feldpausch, JE, Blok, AL, Frederick, EL, Coburn, JW, and Malek, MH. The evolution of the physical work capacity at the fatigue threshold test: past, present, and future. J Strength Cond Res 35(12): 3529-3536, 2021-The assessment of neuromuscular fatigue using surface electromyography has evolved over the past 40 years while maintaining some of the original key features. In this mini-review article, the goal will be to briefly present a history and systems of the physical working capacity at the fatigue threshold (PWCFT). In addition, we will discuss studies that have investigated the effect of different interventions such as supplementation, exercise, and cognitive fatigue to examine what stimuli influence the PWCFT. The latter section of this mini-review will discuss future studies that may provide additional information related to the underlying physiological mechanism(s) that influences the PWCFT. We will conclude with the practical application of PWCFT in health and sports settings.

Using an Electromyography Method While Measuring Oxygen Uptake to Appreciate Physical Exercise Intensity in Adolescent Cyclists: An Analytical Study

Background and Objectives: During physical exercise, the electrical signal of the muscle fibers decreases due to repeated muscle contractions held at different intensities. The measured signal is strongly related to the motor unit activation rate, which is dependent on the chemical mediators and the available energy. By reducing the energy availability, adenosine triphosphate (ATP) production will decrease and therefore the muscle fibers activation rate will be negatively affected. Such aspects become important when taking into account that the training intensity for many young athletes is rather controlled by using the heart rate values. Yet, on many occasions, we have seen differences and lack of relationship between the muscle activation rate, the heart rate values and the lactate accumulation. Materials and Methods: We conducted a prospective analytical study conducted during a 4-month period, on a sample of 30 participants. All study participants underwent an incremental exercise bike test to measure maximum aerobic capacity as well as the muscle activation rate in the vastus lateralis by using an electromyography method (EMG). Results: With age, the EMG signal dropped, as did the electromyography fatigue threshold (EMG_FT) point, as seen through p = 0.0057, r = −0.49, CI95% = −0.73 to −0.16, and electromyography maximum reached point (EMG_MRP) (p = 0.0001, r = −0.64, CI95% = −0.82 to −0.36), whereas power output increased (p = 0.0186, r = 0.427). The higher the power output, the lower the signal seen by measuring active tissue EMG_FT (p = 0.0324, r = −0.39) and EMG_MRP (p = 0.0272, r = −0.40). Yet, with changes in median power output, the power developed in aerobic (p = 0.0087, r = 0.47), mixed (p = 0.0288, r = 0.39), anaerobic (p = 0.0052, r = 0.49) and anaerobic power (p = 0.004, r = 0.50) exercise zones increased. Conclusions: There has been reported a relationship between aerobic/anaerobic ventilatory thresholds (VT₁ and VT₂) and EMG_FT, EMG_MRP, respectively. Each change in oxygen uptake increased the power output in EMG_FT and EMG_MRP, improving performances and therefore overlapping with both ventilatory thresholds.

Repeated Incremental Workbouts Separated by 1 Hour Increase the Electromyographic Fatigue Threshold

ABSTRACT

Bremer, N, Peoples, G, Hasler, B, Litzenburg, R, Johnson, A, and Malek, MH. Repeated incremental workbouts separated by 1 hour increase the electromyographic fatigue threshold. J Strength Cond Res 35(5): 1397-1402, 2021-Studies examining the influence of priming, for continuous exercise, have mainly focused on improved exercise capacity related to oxygen uptake kinetics rather than on neuromuscular fatigue of the muscle. The purpose of this study, therefore, was to determine whether or not the electromyographic fatigue threshold (EMGFT) could be modulated by having subjects perform 2 incremental tests separated by 1 hour. We hypothesized that the EMGFT determined from the second incremental test would be higher than the EMGFT determined from the first incremental test. Nine healthy college-aged men (mean ± SEM: age: 23.8 ± 0.6 years; body mass: 79.5 ± 3.3 kg; height: 1.78 ± 0.02 m) were recruited from the university population. Each subject visited the laboratory on 1 occasion and performed 2 incremental single-leg knee-extensor ergometry to voluntary fatigue separated by 1 hour. The EMGFT was determined for each trial and statistically compared using paired-samples t-test. The results indicated significant mean differences between the EMGFT for the 2 trials (trial 1: 27 ± 1 W vs. trial 2: 34 ± 2 W; p = 0.001), whereas there were no significant mean differences for maximal power output (trial 1: 53 ± 2 W vs. trial 2: 57 ± 2; p = 0.09). These findings suggest that postactivation potentiation may, in part, explain the differences in EMGFT because the exercise mode used in the current study minimizes the cardiorespiratory responses to exercise.

Pre-exhaustion Exercise Differentially Influences Neuromuscular Fatigue Based on Habitual Physical Activity History

ABSTRACT

Harlan, KG, Merucci, RB, Weaver, JJ, Windle, TC, and Malek, MH. Pre-exhaustion exercise differentially influences neuromuscular fatigue based on habitual physical activity history. J Strength Cond Res 35(3): 739-745, 2021-Although there is anecdotal evidence of a potential physiological benefit of pre-exhaustion exercise to enhance muscular recruitment, few studies have systematically examined the effect on neuromuscular activity. Moreover, a subject's habitual physical activity history may, in part, contribute to the muscle's response on a subsequent workbout after a single pre-exhaustion workbout. To date, no studies have examined the effect of pre-exhaustion exercise on the electromyographic fatigue threshold (EMGFT). The purpose of this study, therefore, is to determine whether pre-exhaustion exercise influences the EMGFT. Specifically, we were interested in determining whether or not there is a dichotomous response to pre-exhaustion exercise based on the individual's habitual physical activity history. Thus, we hypothesized that healthy active subjects would have reduced EMGFT values, whereas elite runners would have increased EMGFT values as a result of the pre-exhaustion exercise. Eight healthy college-aged men (mean ± SEM, age = 24.5 ± 0.3 years; body mass = 83.1 ± 3.0 kg; and height = 1.80 ± 0.02 m) and 9 elite runners (mean ± SEM, age = 23.4 ± 0.7 years; body mass = 70.3 ± 2.7 kg; and height = 1.79 ± 0.03 m) participated in current study. Each subject visited the laboratory on 2 occasions separated by 7 days and performed the single-leg knee-extensor ergometry test. For one of the visits, the subjects performed the Thorstensson test (50 continuous, concentric knee extensions) before the single-leg knee-extensor ergometry. The EMGFT was measured on both visits for all subjects. For healthy subjects, we found that the EMGFT was significantly reduced after performing the 50 isokinetic knee extensions (control: 27 ± 6 W vs. Thorstensson: 21 ± 6.0 W; p = 0.001), whereas for elite runners, there was no significant mean differences between the 2 visits (control: 38 ± 3 W vs. Thorstensson: 39 ± 2 W; p = 0.813). These results suggest that 50 repetition of isokinetic muscle action, as a method of pre-exhausting the quadriceps femoris muscles, may be influenced by the subject's habitual exercise history.

Reduced Electromyographic Fatigue Threshold After Performing a Cognitive Fatiguing Task

ABSTRACT

Ferris, JR, Tomlinson, MA, Ward, TN, Pepin, ME, and Malek, MH. Reduced electromyographic fatigue threshold after performing a cognitive fatiguing task. J Strength Cond Res 35(1): 267-274, 2021-Cognitive fatigue tasks performed before exercise may reduce exercise capacity. The electromyographic fatigue threshold (EMGFT) is the highest exercise intensity that can be maintained without significant increase in the electromyography (EMG) amplitude vs. time relationship. To date, no studies have examined the effect of cognitive fatigue on the estimation of the EMGFT. The purpose of this study, therefore, was to determine whether cognitive fatigue before performing exercise reduces the estimated EMGFT. Eight healthy college-aged men were recruited from a university student population and visited the laboratory on multiple occasions. In a randomized order, subjects performed either the cognitive fatigue task (AX continuous performance test) for 60 minutes on one visit (experimental condition) or watched a video on trains for 60 minutes on the other visit (control condition). After each condition, subjects performed the incremental single-leg knee-extensor ergometry test while the EMG amplitude was recorded from the rectus femoris muscle and heart rate was monitored throughout. Thereafter, the EMGFT was calculated for each subject for each visit and compared using paired samples t-test. For exercise outcomes, there were no significant mean differences for maximal power output between the 2 conditions (control: 51 ± 5 vs. fatigue: 50 ± 3 W), but there was a significant decrease in EMGFT between the 2 conditions (control: 31 ± 3 vs. fatigue: 24 ± 2 W; p = 0.013). Moreover, maximal heart rate was significantly different between the 2 conditions (control: 151 ± 5 vs. fatigue: 132 ± 6; p = 0.027). These results suggest that performing the cognitive fatiguing task reduces the EMGFT with a corresponding reduction in maximal heart rate response.

Listening to Fast-Tempo Music Delays the Onset of Neuromuscular Fatigue

Centala, J, Pogorel, C, Pummill, SW, and Malek, MH. Listening to fast-tempo music delays the onset of neuromuscular fatigue. J Strength Cond Res 34(3): 617-622, 2020-Studies determining the effect of music on physical performance have primarily focused on outcomes such as running time to exhaustion, blood lactate, or maximal oxygen uptake. The electromyographic fatigue threshold (EMGFT) is determined through a single incremental test and operationally defined as the highest exercise intensity that can be sustained indefinitely without an increase in EMG activity of the working muscle. To date, no studies have examined the role of fast-tempo music on EMGFT. The purpose of this investigation, therefore, was to determine whether fast-tempo music attenuates neuromuscular fatigue as measured by the EMGFT. We hypothesized that listening to fast-tempo music during exercise would increase the estimated EMGFT compared with the control condition. Secondarily, we hypothesized that maximal power output would also increase as a result of listening to fast-tempo music during the exercise workbout. Ten healthy college-aged men (mean ± SEM: age, 25.3 ± 0.8 years [range from 22 to 31 years]; body mass, 78.3 ± 1.8 kg; height: 1.77 ± 0.02 m) visited the laboratory on 2 occasions separated by 7 days. The EMGFT was determined from an incremental single-leg knee-extensor ergometer for each visit. In a randomized order, subjects either listened to music or no music for the 2 visits. All music was presented as instrumentals and randomized with a tempo ranging between 137 and 160 b·min. The results indicated that listening to fast-tempo music during exercise increased maximal power output (No Music: 48 ± 4; Music: 54 ± 3 W; p = 0.02) and EMGFT (No Music: 27 ± 3; Music: 34 ± 4 W; p = 0.008). There were, however, no significant mean differences between the 2 conditions (no music vs. music) for absolute and relative end-exercise heart rate as well as end-exercise rating of perceived exertion for the exercised leg. These findings suggest that listening to fast-tempo music increased overall exercise tolerance as well as the neuromuscular fatigue threshold. The results are applicable to both sport and rehabilitative settings.