An electromyographic-based test for estimating neuromuscular fatigue during incremental treadmill running

Milk or Kefir, in Comparison to Water, Do Not Enhance Running Time-Trial Performance in Endurance Master Athletes

This study compared flavored kefir (KFR) and flavored milk (MLK) as a recovery drink in endurance master athletes. Using a randomized, placebo-controlled, non-blinded crossover design, 11 males and females completed three testing visits whilst acutely ingesting either KFR, MLK, or water as a placebo (PLA). KFR supplementation occurred for 14 days before the KFR-testing day, followed by a 3-week washout period. Testing visits consisted of an exhausting-exercise (EE) bout, a 4-h rest period where additional carbohydrate feeding was provided, and a treadmill 5 km time trial (TT). The Gastrointestinal Symptom Rating Scale (GSRS) survey was assessed at four timepoints. Blood was collected at baseline and after the TT and was analyzed for I-FABP levels. No significant difference (PLA: 33:39.1 ± 6:29.0 min, KFR: 33:41.1 ± 5:44.4 min, and MLK: 33:36.2 ± 6:40.5 min, p = 0.99) was found between the groups in TT performance. The KFR GSRS total score was significantly lower than the PLA after EE (p = 0.005). No differences in I-FABP were observed between conditions. In conclusion, acute KFR supplementation did not impact TT performance or I-FABP levels but may have reduced subjective GI symptoms surrounding exercise when compared to MLK or PLA.

Impact of probiotic Veillonella atypica FB0054 supplementation on anaerobic capacity and lactate

Seven healthy, physically active men (n = 3) and women (n = 4) (30.7 ± 7.5 years, 172.7 ± 8.7 cm, 70.4 ± 11.6 kg, 23.6 ± 4.1 kg/m2, 49.2 ± 8.4 mL/kg/min) supplemented for 14 days with a placebo (PLA) or 1 × 1010 CFU doses of the probiotic Veillonella atypica FB0054 (FitBiomics, New York, NY). Participants had safety panels, hemodynamics, lactate, and anaerobic capacity assessed. Stool samples were collected to evaluate for metagenomic and metabolomic changes. Exhaustion times were not different between groups, whereas anaerobic capacity tended to shorten with PLA (61.14 ± 72.04 s; 95% CI: -5.49, 127.77 s, p = 0.066) with no change with VA (13.29 ± 100.13 s, 95% CI: -79.32, 105.89 s, p = 0.738). No changes in lactate, hemodynamics, or bacterial community changes were observed, whereas 14 metabolites exhibited differential expression patterns with VA supplementation. In conclusion, VA maintained exercise performance that tended to decline in PLA. Supplementation was well tolerated with no changes in safety markers or reported adverse events.

Changes in Energy Expenditure, Dietary Intake, and Energy Availability Across an Entire Collegiate Women's Basketball Season

ABSTRACT

Zanders, BR, Currier, BS, Harty, PS, Zabriskie, HA, Smith, CR, Stecker, RA, Richmond, SR, Jagim, AR, and Kerksick, CM. Changes in energy expenditure, dietary intake, and energy availability across an entire collegiate women's basketball season. J Strength Cond Res 35(3): 804-810, 2021-The purpose of this study was to identify changes in energy expenditure and dietary intake across an entire women's basketball season. On 5 different occasions across the competitive season, female collegiate basketball players (19.8 ± 1.3 years, 173.9 ± 13.6 cm, 74.6 ± 9.1 kg, 27.1 ± 3.2% fat, 53.9 ± 6.4 ml·kg-1·min-1, n = 13) were outfitted with heart rate and activity monitors over 4 consecutive days and completed 4-day food and fluid records to assess changes in energy expenditure and dietary status. Dual-energy x-ray absorptiometry was used to assess baseline body composition and resting energy expenditure (REE) was measured before and after the season. Data were analyzed using 1-factor repeated-measures analysis of variance. Total daily energy expenditure (TDEE, p = 0.059) and physical activity levels (TDEE/REE, p = 0.060) both tended to decrease throughout the season. Energy balance was negative at all time points throughout the season. Absolute and normalized daily protein intake at the end of the season was significantly (p < 0.05) lower than at the beginning of the season. Carbohydrate (3.7 ± 0.4 g·kg-1·d-1) and protein (1.17 ± 0.16 g·kg-1·d-1) intakes were lower than commonly recommended values based on previously published guidelines. These findings suggest that greater education and interventions for collegiate athletes and coaches regarding dietary intake and energy expenditure are warranted.

Active women demonstrate acute autonomic and hemodynamic shifts following exercise in heat and humidity: A pilot study

The purpose of this study was to assess autonomic and hemodynamic recovery in women who performed moderate-intensity exercise in heat. Seven women (31.7 ± 7.6 years, 67.5 ± 4.4 kg, 25.7 ± 5.6% Fat, 43.9 ± 5.1 mL/kg/min) completed two identical bouts of graded treadmill walking (~60% VO₂peak). One bout was hot (37.5 ± 1.4°C, 46.5 ± 4.6% relative humidity (RH)), and the other was moderate (20.7 ± 1.1°C, 29.9 ± 4.1% RH). For 24 h before and one h after each bout, participants had heart rate variability monitored. After each exercise bout HR and BP were measured during 30 min of supine recovery and 10 min of orthostatic challenge. HF power and RMSSD were lower and LF power and LF:HF ratio greater following exercise in the heat and remained different from the moderate condition for 30 min (p < 0.05). During supine recovery, heat exposure led to higher HR (p = 0.002) and lower DBP (p = 0.016). SBP (p = 0.037) and DBP (p = 0.008) were both lower after 10 min of supine recovery following hot exercise than after moderate temperature. Average response did not reveal orthostatic hypotension despite heat causing a higher HR (p = 0.011) and lower SBP (p = 0.026) after 10 min of orthostatic exposure. Trained women exhibit an autonomic shift toward sympathetic dominance for at least 30 min after exercise in heat. Women who exercise in heat should be wary of an exacerbated HR response after exercise and low recovery blood pressures.

Application of the neuromuscular fatigue threshold treadmill test to muscles of the quadriceps and hamstrings

PURPOSE

The purposes of the present study were: (1) to determine whether the physical working capacity at the fatigue threshold (PWC_FT) model that has been used for estimating the onset of neuromuscular fatigue in the vastus lateralis (VL) during incremental treadmill running could also be applied to the vastus medialis (VM), biceps femoris (BF), and semitendinosus (ST) muscles; and (2) if applicable, to compare the running velocities associated with the PWC_FT among these muscles.

METHODS

Eleven subjects (age 21.7 ± 1.8 years) performed an incremental treadmill test to exhaustion with electromyographic signals recorded from the VL, VM, BF, and ST.

RESULTS

The results indicated there were no significant (p > 0.05) mean differences in the running velocities associated with the PWC_FT for the VL (14.4 ± 2.0 km/h), VM (14.3 ± 1.9 km/h), BF (13.8 ± 1.8 km/h), and ST (14.7 ± 2.3 km/h). In addition, there were significant inter-correlations (r = 0.68-0.88) among running velocities associated with the PWC_FT of each muscle. Individual results also indicated that 9 of the 11 subjects exhibited identical PWC_FT values for at least 3 of the 4 muscles, but there were no uniform patterns for any intra-individual differences.

CONCLUSION

The findings of the present study suggested that the PWC_FT test is a viable method to identify neuromuscular fatigue in the quadriceps and hamstrings during incremental treadmill exercise and results in consistent PWC_FT values among these muscles.

Yeast Beta-Glucan Supplementation Downregulates Markers of Systemic Inflammation after Heated Treadmill Exercise

Aerobic exercise and thermal stress instigate robust challenges to the immune system. Various attempts to modify or supplement the diet have been proposed to bolster the immune system responses. The purpose of this study was to identify the impact of yeast beta-glucan (Saccharomyces cerevisiae) supplementation on exercise-induced muscle damage and inflammation. Healthy, active men (29.6 ± 6.7 years, 178.1 ± 7.2 cm, 83.2 ± 11.2 kg, 49.6 ± 5.1 mL/kg/min, n = 16) and women (30.1 ± 8.9 years, 165.6 ± 4.1 cm, 66.7 ± 10.0 kg, 38.7 ± 5.8 mL/kg/min, n = 15) were randomly assigned in a double-blind and cross-over fashion to supplement for 13 days with either 250 mg/day of yeast beta-glucan (YBG) or a maltodextrin placebo (PLA). Participants arrived fasted and completed a bout of treadmill exercise at 55% peak aerobic capacity (VO_2Peak) in a hot (37.2 ± 1.8 °C) and humid (45.2 ± 8.8%) environment. Prior to and 0, 2, and 72 h after completing exercise, changes in white blood cell counts, pro- and anti-inflammatory cytokines, markers of muscle damage, markers of muscle function, soreness, and profile of mood states (POMS) were assessed. In response to exercise and heat, both groups experienced significant increases in white blood cell counts, plasma creatine kinase and myoglobin, and soreness along with reductions in peak torque and total work with no between-group differences. Concentrations of serum pro-inflammatory cytokines in YBG were lower than PLA for macrophage inflammatory protein 1β (MIP-1β) (p = 0.044) and tended to be lower for interleukin 8 (IL-8) (p = 0.079), monocyte chemoattractment protein 1 (MCP-1) (p = 0.095), and tumor necrosis factor α (TNF-α) (p = 0.085). Paired samples t-tests using delta values between baseline and 72 h post-exercise revealed significant differences between groups for IL-8 (p = 0.044, 95% Confidence Interval (CI): (0.013, 0.938, d = −0.34), MCP-1 (p = 0.038, 95% CI: 0.087, 2.942, d = −0.33), and MIP-1β (p = 0.010, 95% CI: 0.13, 0.85, d = −0.33). POMS outcomes changed across time with anger scores in PLA exhibiting a sharper decline than YBG (p = 0.04). Vigor scores (p = 0.04) in YBG remained stable while scores in PLA were significantly reduced 72 h after exercise. In conclusion, a 13-day prophylactic period of supplementation with 250 mg of yeast-derived beta-glucans invoked favorable changes in cytokine markers of inflammation after completing a prolonged bout of heated treadmill exercise.

Application of a Web-Enabled Leg Training System for the Objective Monitoring and Quantitative Analysis of Exercise-Induced Fatigue

Background

Sustained cardiac rehabilitation is the key intervention in the prevention and treatment of many human diseases. However, implementation of exercise programs can be challenging because of early fatigability in patients with chronic diseases, overweight individuals, and aged people. Current methods of fatigability assessment are based on subjective self-reporting such as rating of perceived exertion or require specialized laboratory conditions and sophisticated equipment. A practical approach allowing objective measurement of exercise-induced fatigue would be useful for the optimization of sustained delivery of cardiac rehabilitation to improve patient outcomes.

Objectives

The objective of this study is to develop and validate an innovative approach, allowing for the objective assessment of exercise-induced fatigue using the Web-enabled leg rehabilitation system.

Methods

MedExercise training devices were equipped with wireless temperature sensors in order to monitor their usage by temperature rise in the resistance unit (Δt°). Since Δt° correlated with the intensity and duration of exercise, this parameter was used to characterize participants’ leg work output (LWO). Personal smart devices such as laptop computers with wireless gateways and relevant software were used for monitoring of self-control training. Connection of smart devices to the Internet and cloud-based software allowed remote monitoring of LWO in participants training at home. Heart rates (HRs) were measured by fingertip pulse oximeters simultaneously with Δt° in 7 healthy volunteers.

Results

Exercise-induced fatigue manifested as the decline of LWO and/or rising HR, which could be observed in real-time. Conversely, training at the steady-state LWO and HR for the entire duration of exercise bout was considered as fatigue-free. The amounts of recommended daily physical activity were expressed as the individual Δt° values reached during 30-minute fatigue-free exercise of moderate intensity resulting in a mean of 8.1°C (SD 1.5°C, N=7). These Δt° values were applied as the thresholds for sending automatic notifications upon taking the personalized LWO doses by self-control training at home. While the mean time of taking LWO doses was 30.3 (SD 4.1) minutes (n=25), analysis of times required to reach the same Δt° by the same participant revealed that longer durations were due to fatigability, manifesting as reduced LWO at the later stages of training bouts. Typically, exercising in the afternoons associated with no fatigue, although longer durations of evening sessions suggested a diurnal fatigability pattern.

Conclusions

This pilot study demonstrated the feasibility of objective monitoring of fatigue development in real-time and online as well as retrospective fatigability quantification by the duration of training bouts to reach the same exercise dose. This simple method of leg training at home accompanied by routine fatigue monitoring might be useful for the optimization of exercise interventions in primary care and special populations.

Wet, volatile, and dry biomarkers of exercise-induced muscle fatigue

Background

The physiological background of exercise-induced muscle fatigue(EIMUF) is only poorly understood. Thus, monitoring of EIMUF by a single or multiple biomarkers(BMs) is under debate.

After a systematic literature review 91 papers were included.

Results

EIMUF is mainly due to depletion of substrates, increased oxidative stress, muscle membrane depolarisation following potassium depletion, muscle hyperthermia, muscle damage, impaired oxygen supply to the muscle, activation of an inflammatory response, or impaired calcium-handling. Dehydration, hyperammonemia, mitochondrial biogenesis, and genetic responses are also discussed. Since EIMUF is dependent on age, sex, degree of fatigue, type, intensity, and duration of exercise, energy supply during exercise, climate, training status (physical fitness), and health status, BMs currently available for monitoring EIMUF have limited reliability. Generally, wet, volatile, and dry BMs are differentiated. Among dry BMs of EIMUF the most promising include power output measures, electrophysiological measures, cardiologic measures, and questionnaires. Among wet BMs of EIMUF those most applicable include markers of ATP-metabolism, of oxidative stress, muscle damage, and inflammation. VO₂-kinetics are used as a volatile BM.

Conclusions

Though the physiology of EIMUF remains to be fully elucidated, some promising BMs have been recently introduced, which together with other BMs, could be useful in monitoring EIMUF. The combination of biomarkers seems to be more efficient than a single biomarker to monitor EIMUF. However, it is essential that efficacy, reliability, and applicability of each BM candidate is validated in appropriate studies.