European Journal of Applied Physiology

Mental fatigue is induced by prolonged engagement in cognitively demanding tasks and impairs endurance performance. The neuropsychophysiological mechanisms underlying this decreased performance remain unclear, with suggestion that mental fatigue may disrupt motor command and consequently muscle activation. We aimed to test this hypothesis in a repeated cross-over design study in which 18 participants completed two experimental sessions involving a time-to-exhaustion cycling test at 80% of peak power output. Each cycling task was preceded by 1h of a prolonged Stroop task (Stroop session) or a neutral control task (Control session). Perception of effort and surface electromyography from ten lower-limb muscles of the right leg were recorded at regular intervals during cycling. Mental fatigue was higher in the Stroop compared to the Control session (p = .002). Endurance cycling time was 111 {+/-} 160 s shorter in the Stroop than in the Control session (p = .009). No significant differences in electromyography parameters were observed between Stroop and Control sessions, for any muscle (p > .05). Perception of effort was higher in the Stroop session from the onset of the cycling task (p = .006), and the rate of increase in perception of effort was significantly higher in the Stroop than Control session (p = .031). Our findings do not support the hypothesis that mental fatigue alters motor control or increases central motor command, as no changes in muscle activation were detected. Conversely, our results reinforce the notion that prolonged cognitive engagement impairs endurance performance primarily through an increased perception of effort. Future research should consider combining surface electromyography with more sensitive neurophysiological techniques to investigate potential subtle changes in motor drive during dynamic, whole-body tasks under mental fatigue. Impact statementOur study confirms that mental fatigue induced by prolonged cognitive exertion impairs cycling endurance performance. By combining measurements of perceptual responses and multi-muscle surface EMG during the endurance task, we observed that the decreased endurance performance is related to an increased perceived effort in the presence of mental fatigue, not related to alterations in motor command.

PURPOSETo get a more detailed description of neuromuscular fatigability, maximal torque sustainability (i.e., the ability to maintain a high torque level) can be assessed in addition to the classically used maximal voluntary contraction (MVC). Since this parameter appears to be affected by mean exercise torque (MET), the present study aims to examine the relationship between MET and neuromuscular fatigability induced by exhausting contractions. METHODSThirteen participants sustained a plantar flexors MVC for 1 min (MVC1- MIN) before and after exhausting exercises designed to produce a similar MET (30% MVC), and following a 10-min rest period. Exercises consisted of intermittent (INT), continuous (CON) or variable (continuous contraction alternating between moderate and low intensity, VAR) contractions performed until task failure. RESULTSAlthough the INT resulted in greater exercise duration and torque-time integral than CON and VAR, MVC similarly decreased after all exercises due to neural and muscular impairments. The torque loss during the MVC1-MIN increased after all exercises to a similar extent, mainly because of neural alterations. Contrary to MVC, the torque loss during the MVC1-MIN returned to baseline value after the recovery period. CONCLUSIONBy considering both maximal torque production and sustainability, INT, CON and VAR exercises, performed with identical mean torque and until exhaustion, led to a similar neuromuscular fatigability. Results confirm the independence of maximal torque production from the contraction pattern and support the impact of MET on maximal torque sustainability. The present findings are crucial to consider for the management of neuromuscular fatigability in both athletes and patients.

BackgroundPushing/pulling isometric muscle actions (PIMA) are commonly used to assess strength, fatigability, and neuromechanical function, whereas holding isometric muscle actions (HIMA), applied in rehabilitation and performance settings, remain less clearly defined and comparatively understudied. Evidence suggests that PIMA and HIMA may elicit distinct neural and cardiovascular responses, yet inconsistent operational definitions complicate interpretation and application. This review synthesized research directly comparing PIMA and HIMA to clarify their physiological profiles, identify research gaps and explore practical relevance. MethodsThe protocol was pre-registered with PROSPERO (CRD42024530386). Databases were searched for peer-reviewed studies comparing PIMA and HIMA. Study quality and risk-of-bias were evaluated, and meta-analyses and meta-regressions were performed on time-to-task-failure (TTF), ratings of perceived exertion (RPE), heart rate (HR), and mean arterial pressure (MAP). ResultsFifty-four studies (publication year 2012.9{+/-}6.9; 1995-2024) were identified (N=919 participants; [~]29.8{+/-}10.7 years). Thirty-five studies reported performance measures, 45 examined neural outputs, and 14 assessed cardiovascular or metabolic responses. Meta-analysis revealed longer TTF for PIMA vs. HIMA at the same absolute intensity (n=407; g=-0.74, p<0.001), except for two studies on axial muscles (g=1.78-3.59, p<0.001). Individual-study patterns suggest diminishing TTF differences at higher intensities; however, since two other studies found clear differences, this may reflect methodological heterogeneity rather than a true intensity effect. No significant differences were identified for HR, MAP, or RPE at relative time points, except for higher RPE at 50%TTF during PIMA. Qualitatively, PIMA was associated with higher peak torques and discharge rates, whereas HIMA was associated with higher burst rates, glucose uptake, and force fluctuation increases. ConclusionsThese mechanistic distinctions may hold practical relevance as PIMA may be beneficial for prolonged activation and agonist neuromuscular adaptations. In contrast, HIMA could provide diagnostic value, injury-prevention potential, and time-efficient muscular, neural, and cardiovascular adaptations in rehabilitation. Methods varied widely across studies, making additional meta-analyses impossible. Randomized controlled trials are required to confirm the use of PIMA vs HIMA in clinical or performance contexts. Key PointsO_LIPushing/pulling and holding isometric actions produce distinct neuromuscular and physiological responses and should not be considered equivalent. C_LIO_LIPushing/pulling actions generally support longer force maintenance, with task- and muscle-specific exceptions. C_LIO_LINeural, mechanical, and metabolic characteristics differ, with pushing/pulling emphasizing antagonist force output while holding is more neuromuscular complex and metabolically taxing. C_LIO_LIThese differences suggest divergent applications, with pushing/pulling suited to performance goals and holding suited to rehabilitation and specific diagnostic contexts. C_LI

Mental fatigue (MF) does not only affect cognitive but also physical performance. This study aimed to explore the effects of MF on muscle endurance, rate of perceived exertion (RPE), and motor units activity. Ten healthy males participated in a randomised crossover study. The subjects attended two identical experimental sessions separated by three days with the only difference of a cognitive task (incongruent Stroop task [ST]) and a control condition (watching a documentary). Perceived MF and motivation were measured for each session at baseline and after each cognitive task. Four contractions at 20% of maximal voluntary contraction (MVIC) were performed at baseline, after each cognitive and after muscle endurance task while measuring motor units by high-density surface electromyography. Muscle endurance until failure at 50% of MVIC was measured after each cognitive task and the RPE was measured right after failure. ST significantly increased MF (p = 0.001) reduced the motivation (p = 0.008) for the subsequent physical task and also impaired physical performance (p = 0.044). However, estimates of common synaptic inputs and motor unit discharge rates as well as RPE were not affected by MF (p> 0.11). In conclusion, MF impairs muscle endurance and motivation for the physical task but not the neural drive to the muscle at any frequency bands. Although it is physiologically possible for mentally fatigued subjects to generate an optimal neuromuscular function, the altered perception and motivation seems to limit physical performance. Our results suggest that the corticospinal pathways are not affected by MF.

Isokinetic dynamometry and neuromuscular electrical stimulation (NMES) are two commonly used approaches for quantifying muscle contractile properties. Few studies, however, have investigated the relationship between such testing procedures, particularly in women. PURPOSETo determine the relationship between voluntary isometric and isokinetic torque and torque during involuntary, electrically evoked contractions of the knee extensor muscles. METHODSThirty young women (age 23 {+/-} 5 y) performed maximal knee extensions on an isokinetic dynamometer at angular velocities of 0, 1.57, 3.14, 4.71, and 6.28 rad/s. Following this testing, NMES of the quadriceps (400 V, 200 {micro}s) was used to determine unpotentiated and potentiated twitch contractile properties. The quadriceps were also stimulated with 1 s trains at 1, 5, 10, 15, 20, 25, 30, 35, 40, 60, 80, and 100 Hz to determine the torque-frequency relationship. RESULTSVoluntary torques at 1.57 and 3.14 rad/s were significantly correlated (i.e., multiplicity-adjusted P[&le;]0.01) with the rate of torque development during potentiated twitches (r = 0.60 and 0.55, respectively). No other significant correlations were found between voluntary and involuntary muscle contractile properties, including various measures of the torque-frequency relationship. CONCLUSIONAlthough there is some relationship between voluntary and NMES indices of muscle contractility, such results are only moderately well-correlated at best. The two techniques should therefore be considered complementary rather than interchangeable. O_FIG O_LINKSMALLFIG WIDTH=191 HEIGHT=200 SRC="FIGDIR/small/24316419v1_ufig1.gif" ALT="Figure 1"> View larger version (32K): org.highwire.dtl.DTLVardef@8e14b7org.highwire.dtl.DTLVardef@1f22be7org.highwire.dtl.DTLVardef@2052deorg.highwire.dtl.DTLVardef@20a02d_HPS_FORMAT_FIGEXP M_FIG C_FIG

BackgroundInter-set rest intervals (ISR) influence resistance training adaptations. Shorter intervals (<60s) promote metabolic stress, while longer intervals (>60s) are thought to enhance recovery, mechanical tension, and strength. AimThe systematic review and meta-analysis examined the effects of <60s vs. >60s ISR on hypertrophy, strength, and secondary outcomes in resistance-trained males. MethodsSix studies met the inclusion criteria, evaluating muscle hypertrophy, strength, metabolic hormones, power output, and motor unit recruitment. Standardised mean differences (SMDs) with 95% confidence intervals (CIs) were calculated, and forest plots were generated to visualise pooled effects. ResultsStrength was modestly improved with longer ISRs (SMD = -0.74) but only trivial differences in hypertrophy (SMD = 0.08). Metabolic hormone responses showed negligible variation between conditions (SMD = 0.11). Secondary outcomes were mixed, with motor unit recruitment slightly favouring shorter ISRs (SMD = -0.66), while power output tended to favour longer ISRs (SMD = -0.64). Forest plots illustrated the heterogeneity of effects across studies. ConclusionShorter ISRs appear to slightly reduce strength and power outcomes, while longer ISRs offer minimal benefit for hypertrophy. These findings suggest that longer ISRs may not confer superior benefits for muscle growth, as previously assumed in the literature (e.g., Schoenfeld, 2016). The variability across outcomes underscores the need for further research to refine ISR recommendations, particularly in trained individuals. What is already known on this topicO_LIInter-set rest intervals (ISR) influence hypertrophy and strength outcomes in resistance training. C_LIO_LIShort rest (<60 s) increases metabolic stress but may impair recovery and force output. C_LIO_LILonger rest (>60 s) consistently supports strength gains, but evidence for hypertrophy advantages remains inconclusive. C_LI What this study addsO_LISynthesises evidence specifically in resistance-trained males ([&ge;]1 year RT experience). C_LIO_LIShows hypertrophy outcomes are trivial and do not favour longer ISRs over shorter ISRs. C_LIO_LIConfirms longer ISRs modestly improve strength and power, while hormonal and motor unit responses remain inconsistent. C_LIO_LIUnderscores the absence of robust evidence supporting longer ISRs as a superior hypertrophy strategy in trained populations. C_LI

ObjectiveTo investigate the relationship between rate of torque development (RTD) and corticospinal excitability (denoted by motor-evoked potential; MEP) during explosive voluntary contractions. Also, to assess differences in MEP and silent period duration between different phases of explosive contraction and at maximum voluntary contraction (MVC) plateau. MethodsIn 14 adults, quadriceps muscle MEP and silent period duration were measured at [~]45 (early), [~]115 (middle), and [~]190 ms (late) from EMG onset during knee-extensor isometric explosive contractions, and at MVC plateau with superimposed transcranial magnetic stimulation (TMS). RTD was measured immediately prior to early-phase MEP during the same contractions, and these two variables were correlated across separate contractions, within participants, via repeated measures correlation (RmCorr). RTD was also measured in explosive contractions without TMS over early-, middle-, and late-phases and correlated to MEP averaged across the corresponding and preceding phases, via Pearsons r correlations, assessing relationships across participants. MEP and silent period duration were compared (ANOVA) between the different phases and at MVC plateau. ResultsMEP and RTD were correlated across separate contractions within participants (RmCorr r=0.43), and in the middle phase across participants (Pearsons r=0.56). MEP and RTD were not correlated in other phases (r[&ge;]0.09). Silent period duration increased throughout the different phases of contraction and up to MVC plateau (ANOVA, p=0.001) but MEP remained constant (ANOVA, p=0.42). ConclusionThe correlations between MEP and RTD suggests corticospinal excitability is an important determinant of RTD. During rapid torque development and up to MVC plateau, corticospinal inhibition increases but excitability remains constant.

The present study aimed to characterise the temporal recovery pattern of contralateral-homologous torque following a bout of unilateral resistance exercise (RE). Ten young, healthy, recreationally active, resistance-trained men performed 10 sets of 10 repetitions of knee extensor (KE) contractions at 50 % 1RM with 1 min rest between sets. Isometric maximal voluntary contraction (MVC) peak torque (PT), surface electromyography (sEMG), muscle soreness and serum creatine kinase (CK) levels were assessed immediately before and 5 min after RE cessation, and then +4 h, +24 h, +48 h and +72 h later. Data are presented as mean [95 % CI] % change from pre-exercise values. RE evoked a minor increase in CK and pain in the late recovery period (+24 h to +72 h) (P < 0.034) and decreases in ipsilateral KE PT were observed immediately post-exercise (-26 [-33, -18] %, P < 0.001) and up to +48 h (-12 [-19, -4] %, P = 0.006). Measurable decreases in PT were also observed in the non-exercised contralateral KE immediately post-exercise (-8 [-13, -3] %, P = 0.006) up to +24 h (-8 [-15, 0] %, P = 0.020), but were significantly lower than the ipsilateral KE PT (P < 0.05). These findings suggest the presence of crossover fatigue following RE in young, healthy, active, resistance-trained men, however, the magnitude and temporal recovery are substantially less severe and protracted in the contralateral homologous KE.

Whilst people typically chose to locomote in most economical fashion, during cycling on a bicycle they will, unusually, chose cadences that are higher than metabolically optimal. Empirical measurements of the intrinsic contractile properties of the vastus lateralis (VL) muscle during submaximal cycling suggest that the cadences that people prefer (i.e., self-selected cadences: SSC) allow for optimal muscle fascicle shortening velocity for the production of knee extensor muscle power. It remains unclear, however, whether this is consistent across different power outputs where SSC is known to might be affected. We examined the effect of cadence and external power requirements on muscle neuromechanics and joint powers during cycling. VL fascicle shortening velocities, muscle activations and joint-specific powers were measured during cycling between 60 and 120rpm (and the SSC), while participants produced 10%, 30%, and 50% of peak maximal power. VL shortening velocity increased as cadence increased but was similar across the different power outputs. Although no differences were found in the distribution of joint powers across cadence conditions, the absolute knee joint power increased with increasing crank power output. Muscle fascicle shortening velocities increase in VL at the SSC as pedal power demands increase from submaximal to maximal cycling. It therefore seems highly unlikely that preferred cadence is primarily driven by the desire to maintain "optimal" muscle fascicle shortening velocities. A secondary analysis of muscle activation patterns revealed that minimizing muscle activation is likely more important when choosing a cadence for given pedal power demand.

PurposeRecent research has explored region-specific responses within the biceps femoris long head. However, evidence on regional muscle activation remains controversial, primarily because information derived solely from surface electromyograms (sEMG) amplitude does not necessarily provide an accurate estimate of neural drive to the muscle. To address this limitation, this study investigated whether there are proximodistal differences in motor unit properties of the biceps femoris long head during isometric hip extension and knee flexion tasks. MethodsSeventeen resistance-trained males performed isometric knee flexion and hip extension tasks at 20% and 40% of maximal voluntary contraction. High-density sEMG were recorded from proximal and distal regions of the biceps femoris long head and decomposed into individual motor units. Central motor unit properties (mean discharge rate, discharge rate variability, recruitment and de-recruitment thresholds) and action potential properties (amplitude and conduction velocity) were analyzed. Bipolar sEMG amplitude was also calculated for each region to simulate traditional sEMG measurements. ResultsBipolar sEMG amplitude, motor unit action potential amplitude and conduction velocity were significantly greater in the distal region during both tasks. In contrast, no proximodistal differences were observed in central motor unit properties. ConclusionThese findings suggest that increased bipolar sEMG amplitude in the distal region of the biceps femoris long head is driven by motor unit action potential properties rather than differences in central modulation, likely influenced by intra-muscular variations in muscle mechanics and geometry. This emphasizes limitations of relying solely on sEMG amplitude to infer neural control strategies in the biceps femoris long head.

Severe-intensity constant work rate (CWR) cycling tests are useful for monitoring training progression and adaptation as they impose significant physiological and psychological strain and thus simulate the high-intensity competition environment. However, fatiguing tests require substantial recovery and may disrupt athlete training or competition preparation. Therefore, the development of a brief, minimally fatiguing test providing comparable information is desirable. PurposeTo determine whether physiological variables measured during, and functional decline in maximal power output immediately after, a 2-min CWR test can act as a proxy for 4-min test outcomes. MethodsPhysiological stress was monitored and pre-to-post-CWR changes in 10-s sprint power computed (to estimate performance fatigability) during 2- and 4-min CWR tests in high-level cyclists. ResultsThe 2-min CWR test evoked a smaller decline in sprint mechanical power (32% vs. 47%, p<0.001), however both the physiological variables and sprint mechanical power were independently and strongly correlated between 2- and 4-min tests. Differences in V{middle dot}O2peak and blood lactate concentration in both CWR tests were strongly associated with the decline in sprint mechanical power. ConclusionPhysiological variables measured during, and the loss in sprint mechanical power measured after, a severe-intensity 2-min CWR test were less than in the 4-min test. Yet strong correlations between 2- and 4-min test outcomes indicated that the 2-min test can be used as a proxy for the longer test. Because shorter tests are less strenuous, they should have less impact on training and competition preparation and may therefore be more practically applicable within the elite performance environment.

BackgroundThe effects of hardstyle kettlebell training are increasingly cited in strength and conditioning research, yet reference data from a proficient swing is scarce. The aim of this exploratory study was to investigate the force profile of a two-handed hardstyle swing performed by a Russian Kettlebell Challenge (RKC) instructor. MethodsThe subject is a 44-year-old male, body mass 75.6 kg, height 173.5 cm, with six years of regular hardstyle training experience. Two-handed hardstyle swings were performed with a series of incremental mass kettlebells (8-68 kg). Ground reaction force (GRFs) was obtained from a floor-mounted force platform. Force-time curves (FTCs), peak force, forward force, rate of force development (RFD) and swing cadence were investigated. ResultsData revealed the FTC of a proficient swing is highly consistent and dominated by a single force peak (mean SD = 47 N), with a profile that remained largely unchanged to 24 kg. Pearson correlation analysis revealed a very strong positive correlation in peak force with kettlebell mass (r = 0.95), which increased disproportionately from the lightest to heaviest kettlebells; net peak force increased from 8.36 {+/-} 0.75 N.kg-1 (0.85 x BW) to 12.82 {+/-} 0.39 N.kg-1 (1.3x BW). There was a strong negative correlation between RFD and kettlebell mass (r = 0.82) that decreased from 39.2 N.s-1.kg-1 to 21.5 N.s-1.kg-1. There was a very strong positive correlation in forward ground reaction force with kettlebell mass (r = 0.99), expressed as a ratio of vertical ground reaction, that increased from 0.092 (9.2%) to 0.205 (20.5%). Swing cadence exceeded 40 swings per minute (SPM) with all kettlebells. ConclusionOur findings challenge some of the popular beliefs of the hardstyle kettlebell swing. Consistent with hardstyle practice, and previous kinematic analysis of expert and novice, force-time curves show a characteristic single large force peak, differentiating passive from active shoulder flexion. Ground reaction force did not increase proportionate to kettlebell mass, with a magnitude of forward force smaller than described in practice. These results could be useful for coaches and trainers wanting to improve athletic performance, and healthcare providers using the kettlebell swing for therapeutic purposes. Findings from this study were used to inform the BELL Trial, a pragmatic controlled trial of kettlebell training with older adults. www.anzctr.org.au ACTRN12619001177145.

PurposeAn oxygen uptake ([V]O2) plateau, despite an increased work rate, is considered the gold standard for confirming if exercise test performance reflects maximal oxygen uptake ([V]O2max). We investigated whether adolescents demonstrate a [V]O2 plateau during an incremental test or if a supramaximal verification phase is necessary to confirm [V]O2max. We also investigated the impact of using moving versus binned time averages on [V]O2max values, and how these processing strategies influence the interpretation of the verification phase in confirming [V]O2max. MethodsA total of 27 adolescents (16 girls) aged 12 to 14 years completed an incremental cycle ergometer ramp test to exhaustion. After a 15-minute recovery, a verification phase was conducted at 105% of their incremental test peak power. [V]O2max was analysed using 15-second binned and moving averages. ResultsOut of 27 participants, 5 (19%) demonstrated a plateau in [V]O2 during an incremental test. [V]O2max was confirmed in the verification phase for 23 out of the 27 adolescents (85%). The moving [V]O2max (mL/kg/min) averages were higher than the binned [V]O2 values in the incremental test (1.8%) and the verification phase (2.4%) (P<0.0001). Processing strategies did not affect the confirmation of [V]O2max. ConclusionA verification phase is necessary for accurately determining [V]O2max in adolescents, who often do not reach a [V]O2 plateau. The processing strategies of exercise tests should be reported, as different strategies can lead to variations in [V]O2max results. However, these processing strategies do not impact the utility of the verification test.

PurposeThere is growing emphasis on investigating heterogeneity in resistance training (RT) outcomes, likely motivated by observations of substantial gross variability in training effects. However, gross variability does not necessarily represent true inter-individual response variation (IRV) and can be obscured by measurement error, sampling variance, and biological variability. Appropriate study design and statistical analysis are required to distinguish IRV from these confounding sources of within-participant variation. Methods16 recreationally trained participants completed a novel replicated within-participant unilateral design across two 11-week training phases separated by a 6-8 week washout. Lower limbs were randomized to a low volume ([~]8 sets/week) or high volume ([~]16 sets/week) training protocol in each phase. We assessed both general (GEN; average response across conditions) and condition-specific (CON; difference between volumes) IRV for vastus lateralis cross-sectional area and leg press one-repetition maximum using a multi-stage statistical approach. ResultsHigher weekly set volumes demonstrated a detectable advantage for muscle hypertrophy (1.8 cm{superscript 2} [95% HDI: 0.29, 3.41]; 98.77% posterior probability) but not maximal strength (3.48 kg [95% HDI: -5.1, 12.15]; 80.01% posterior probability). Despite substantial gross variability, we failed to detect irrefutable evidence of meaningful IRV. Integrated methods revealed stronger evidence for GEN versus CON IRV, with correlation coefficients ranging from 0.67 to 0.7 for GEN versus 0.04 to 0.06 for CON. ConclusionsOur findings clearly illustrate that gross variability in training outcomes does not necessarily indicate true inter-individual differences, a distinction critical for both research and practice. KEY POINTSO_LIGross variability in resistance training outcomes is commonly interpreted as evidence of meaningful inter-individual response variation (IRV), but this variability often reflects confounding sources of within-participant variation rather than true inter-individual differences. C_LIO_LIUsing a novel replicated within-participant unilateral design, we investigated the effects of different weekly set volumes on changes in muscle size and maximal strength, as well as the inter-individual variation thereof. C_LIO_LIAt the group level, higher weekly set volumes produced modest but detectable benefits for muscle hypertrophy but not maximal strength. At the individual level, we failed to reveal irrefutable evidence of true IRV for either primary outcome, though there was stronger support for variability in training responses independent of weekly set volume (i.e., general IRV) compared to differential responses between volume conditions (i.e., condition-specific IRV). C_LIO_LIWhile this study has limitations, it highlights that appropriate study design and statistical analysis are essential for investigating IRV in resistance training. Our findings, along with the broader research in multiple disciplines (i.e., medicine, nutrition science, and exercise physiology), demonstrate that gross variability can purely reflect confounding sources of within-participant variation (e.g., sampling variance, measurement error, biological variability) rather than true inter-individual differences--a distinction critical for both research and practice. C_LI

The study aimed to analyze the effects of functional training (FT) on athletes muscle strength compared to traditional resistance training (TRT). A systematic search was conducted in 6 databases from inception to January 2024. Baseline and outcome measures from randomized controlled trials (RCT) were assessed for the impact of FT on athlete muscle strength, across sex, age, and sports levels. Hedges g effect sizes were calculated using a random-effects model, and subgroup and single training factor analyses were performed to address potential sources of heterogeneity, along with a meta-regression analysis. The inclusion of 67 studies involving 1718 athletes revealed significant moderate to large effects of FT on maximum strength (k=11; ES=2.68; p[&le;] 0.001), power (k=12; ES=0.68; p<0.001), as well as muscle endurance(k=12; ES=4.13; p<0.001).In conclusion, FT appears to offer potential benefits for enhancing muscle strength in athletes, with considerations for individual differences in sex, age, and training programs. Findings suggest that longer training sessions may be associated with improvements in maximum strength and muscle endurance, whereas shorter sessions might be more conducive to power development. Additionally, preliminary evidence hints that younger athletes may experience more pronounced training benefits, though this observation requires further investigation to establish a more definitive correlation.

PurposeTo characterise the mechanical and neuromuscular response of lower limb muscles in subjects undergoing Whole Body Vibration (WBV) at different frequencies while holding two static postures. MethodsTwenty-five participants underwent WBV at 15, 20, 25 and 30 Hz while holding a static hack squat and on fore feet posture. Surface electromyography (sEMG) and soft tissue accelerations were collected from Gastrocnemius Lateralis (GL), Soleus (SOL) and Tibialis Anterior (TA) muscles. ResultsOnly specific WBV settings led to a significant increase in muscle contraction. Specifically, the WBV-induced activation of SOL and GL was maximal in fore-feet and in response to higher frequencies. Estimated displacement at muscle bellies revealed a resonant pattern never highlighted before. After stimulation starts, muscle oscillation reaches a peak followed by a drop and a further stabilisation (few seconds after the peak) that suggests the occurrence of a neuromuscular activation to reduce the vibration-induced oscillation. ConclusionLower leg muscles need a response time to tune to a vibratory stimulation, which discourages the use of dynamic exercises on vibrating platforms. To maximize calf muscle response to WBVs, a stimulation frequency in the range of 25-30 Hz and an on fore feet posture are recommended.

Increases in speed or slope promote different adjustments in the locomotor system and lead to a higher heart rate (HR). Because heart rate variability (HRV) is known to respond to exercise intensity and to biomechanical stimuli, we aimed to answer whether HRV would be sensitive to changes in speed and/or slope under similar HR. We hypothesize that HRV would depend solely on HR. To test this hypothesis, 6 healthy male runners (age 30 {+/-} 7.5 yrs.) were recruited and a velocity V, with similar HR/HRmax was selected per volunteer. Changes in HR were referred to these particular velocities V, resulting in comparable exercise intensities. HRV was estimated through standard deviation (sdt) and root mean square of successive RR intervals (rmst), normalized per volunteer. Four running conditions were compared. We found that rmst decreased with speed and slope, with significant interaction between the independent variables. The run {0.7 V, 0% slope} was different from the remaining 3 conditions, which, in turn, were no different from one another. Thus, this estimator did not show a distinct sensitivity to variations in speed or slope. On the other hand, sdt decreased with both speed and slope, with no significant interactions. The runs performed at {0.7 V, 0% slope} and {0.7 V, 6% slope} were different from those at {1 V, 0% slope} and {1 V, 6% slope}. Therefore, sdt presented different values under similar HR. This finding leads us to conclude that cardiac control operates sensitively due to the mode of the changes imposed on the metabolic demand. Summary StatementDoes heart rate variability respond similarly to running in different combinations of speed and slope? While one estimator depended on the exercise intensity, another was sensitive to the running conditions.

ObjectiveTandem cycling requires a coordinated effort between the pilot and the stoker. Previous research suggests that randomly paired tandem cyclists produce lower power output than when cycling solo. This study examined how a cyclists individual ability and their position on the tandem (pilot or stoker) affects pair performance, when partners are either closely matched or differ substantially in solo cycling capacity, as this might be relevant for training and selection. MethodsTwenty-three trained cyclists completed three 10-minute time trials: solo, equal-capacity tandem ([&le;]25 W difference in solo performance), and unequal-capacity tandem ([&ge;]40 W difference). Mean power output, heart rate, cadence, and rating of perceived exertion (RPE) were recorded. Positions (pilot or stoker) were counterbalanced. Linear mixed-effects models assessed effects of capacity and position. ResultsRelative to solo cycling, equal-capacity tandem pairs revealed lower power output (-3.9%), lower heart rate (-2.3%), and lower RPE (-11.5%). Unequal-capacity tandems differed from solo only in heart rate (-2.7%). Stokers produced lower power relative to solo (-5.3%) and relative to pilots (-3.7%) and reported lower RPE relative to solo (-13.9%), while pilots matched their solo power at a lower heart rate (-2.9%). Cadence did not differ across conditions. Total tandem power averaged 95.6% of combined solo power, and differences in partner capacity did not significantly affect combined power output. ConclusionThis study provides the first known experimental data on how partner matching affects individual and combined power output in tandem cycling. Equal- and unequal-capacity tandem pairs showed similar performance. Lower power and RPE among stokers suggest reduced engagement or a redistribution of effort between riders. These findings highlight that effective tandem performance depends on physiological capacity and rider position on the tandem, but not on the difference in capacity between partners.

Individuals with high fatigue resistance against a high-intensity conditioning activity (CA) may be able to avoid experiencing significant fatigue and enhance their voluntary performance. We examined whether the optimal contraction duration of dynamic knee extension exercises to maximize subsequent voluntary performance varies depending on the strength level of an individual. The study participants were 22 male American college football players. Initially, all participants performed a 10-s maximal isometric knee extension exercise and were classified as stronger individuals (n = 8) and weaker individuals (n = 8) based on their relative muscle strength. Each group then performed three types of dynamic CA with different contraction durations (6 s [6-CA], 12 s [12-CA], and 18 s [18-CA]) in random order. To observe the time-course changes in post-activation potentiation and performance enhancement, the twitch torques induced by electrical stimulation and isokinetic knee extension torques at 180{degrees}/s were recorded before and after each CA. The twitch torque increased at 10 s (29.5% {+/-} 9.3%) and 1 min (18.5% {+/-} 6.8%) after 6-CA for the stronger individuals (p < 0.05). However, no post-activation potentiation was induced in the weaker individuals in either protocol. Voluntary performance increased at 4 (7.0% {+/-} 4.5%) and 7 (8.2% {+/-} 4.3%) min after 18-CA for stronger individuals (p < 0.05). However, there was no post-activation performance enhancement in either protocol for weaker individuals. Thus, CA with a relatively long contraction duration was optimal to maximize the subsequent voluntary performance for stronger individuals. It remains unknown whether CAs performed with relatively short or long contraction durations were optimal for weaker individuals.

The ability to withstand impairments in key physiological variables during prolonged exercise, known as durability, is emerging as an important factor in cycling performance. While females possess physiological characteristics that could confer enhanced durability relative to males, little is known about potential sex differences. 32 trained cyclists (16 males and 16 females) performed an incremental exercise test to exhaustion in visit 1. In visit 2 they performed 90 minutes of heavy intensity cycling (HVY) at 110% of gas exchange threshold (GET), followed by another incremental test. During HVY, pulmonary gas exchange ([V]O2 and [V]CO2) ventilation ([V]E), heart rate (HR), rating of perceived exertion (RPE), near-infrared spectroscopy and electromyography were recorded, and blood lactate (BLa) was collected. Before and after HVY, maximal voluntary contraction (MVIC), voluntary activation (VA) and potentiated twitches (100Hz, 10Hz, Qtw{middle dot}pot) of the knee extensors were assessed. Power at GET (-16{+/-}15% vs -2{+/-}13%) and respiratory compensation point (-13{+/-}10% vs -6{+/-}9%) decreased more in males than females (P[&le;]0.049). All aspects of neuromuscular function decreased from pre to post (all P<0.001), without sex differences (P[&ge;]0.096). During HVY, HR, [V]O2 (%peak), relative energy expenditure increased more in males (P[&le;]0.008), whereas respiratory exchange ratio decreased more in females (P=0.001). BLa was higher in males than females (P=0.030). Muscle oxygen extraction was lower (P=0.004) and tissue saturation index higher for females (P<0.001). The smaller reductions exhibited by females in submaximal thresholds, associated with lesser derangements to oxidative efficiency, highlight the need to consider sex-specific training prescription and pacing strategies for long duration events. Key PointsO_LIDurability, as measured by the reduction in incremental exercise test outcomes, is relatively unexplored in females compared to males, despite physiological sex differences that might confer a female advantage. C_LIO_LIAfter 90 minutes of heavy intensity cycling, males demonstrated greater reductions in the power outputs associated with gas exchange threshold and respiratory compensation point. C_LIO_LIThe maximal rate of oxygen consumption and incremental test peak power output decreased similarly in both sexes. C_LIO_LIThese changes are associated with greater carbohydrate metabolism and losses of efficiency in males, whereas no sex differences were observed in neuromuscular fatigue. C_LI