High-Density Electromyography Excitation in Front vs. Back Lat Pull-Down Prime Movers.

The current study compared the spatial excitation of the primary muscles during the lat pull-down exercise with the bar passing in front (front-LPD) or behind the neck (back-LPD) using high-density electromyography. Fourteen resistance trained men performed a front-LPD or a back-LPD within a non-fatiguing set with 8-RM as the external load. The muscle excitation centroid of latissimus dorsi, middle trapezius, pectoralis major, biceps brachii, triceps brachii and posterior deltoid muscles were recorded during the ascending and the descending phase. During the descending phase, the front-LPD showed superior excitation of the latissimus dorsi (ES = 0.97) and the pectoralis major (ES = 1.17), while in the ascending phase, the back-LPD exhibited superior excitation of the latissimus dorsi (ES = 0.63), and the front-LPD showed superior excitation of the biceps brachii (ES = 0.41) and the posterior deltoid (ES = 1.77). During the descending phase, the front-LPD showed a more lateral centroid of the latissimus dorsi (ES = 0.60), the biceps brachii (ES = 0.63) and the triceps brachii (ES = 0.98), while the centroid was more medial for the middle trapezius (ES = 0.58). The centroid of the middle trapezius was also more medial in the front-LPD during the ascending phase (ES = 0.85). The pectoralis major centroid was more cranial in the front-LPD for both the descending (ES = 1.58) and the ascending phase (ES = 0.88). The front-LPD appears to provide overall greater excitation in the prime movers. However, distinct spatial excitation patterns were observed, making exercise suitable for the training routine.

Synergistic difference in the effect of stretching on electromechanical delay components.

This study investigated the synergistic difference in the effect of stretching on electromechanical delay (EMD) and its components, using a simultaneous recording of electromyographic, mechanomyographic, and force signals. Twenty-six healthy men underwent plantar flexors passive stretching. Before and after stretching, the electrochemical and mechanical components of the EMD and the relaxation EMD (R-EMD) were calculated in gastrocnemius medialis (GM), lateralis (GL) and soleus (SOL) during a supramaximal motor point stimulation. Additionally, joint passive stiffness was assessed. At baseline, the mechanical components of EMD and R-EMD were longer in GM and GL than SOL (Cohen's d from 1.78 to 3.67). Stretching decreased joint passive stiffness [-22(8)%, d = -1.96] while overall lengthened the electrochemical and mechanical EMD. The mechanical R-EMD components were affected more in GM [21(2)%] and GL [22(2)%] than SOL [12(1)%], with d ranging from 0.63 to 1.81. Negative correlations between joint passive stiffness with EMD and R-EMD mechanical components were found before and after stretching in all muscles (r from -0.477 to -0.926; P from 0.007 to <0.001). These results suggest that stretching plantar flexors affected GM and GL more than SOL. Future research should calculate EMD and R-EMD to further investigate the mechanical adaptations induced by passive stretching in synergistic muscles.

Speed Effects on the Accuracy of Heart Rate as Oxygen-Uptake Indicator in Short-Distance Shuttle Running.

Purpose: Despite the accuracy of heart rate (HR) as an indicator of the aerobic engagement has been evaluated in several intermittent on-court activities, its validity as an oxygen uptake (V˙O2) indicator during shuttle running over short paths remains uncertain. Moreover, it is unclear whether speed may affect such validity. This study evaluated the HR ability in estimating the V˙O2 during 5-m shuttle running at different speeds. Methods: V˙O2 and HR of 12 physically active young men were recorded during an incremental forward running (FW) protocol and a 5-m shuttle test at 50%, 60%, and 75% of maximal aerobic speed (MAS). Slope and intercept of the relationship between HR and V˙O2 (HR/V˙O2) were individually determined, in both protocols. The HR measured during the shuttle test was used in the FW HR/V˙O2 to estimate V˙O2 at each shuttle speed. A paired Student's t-test compared slopes and intercepts of the two HR/V˙O2. A two-way RM-ANOVA and an equality test examined, respectively, the differences and the equality between measured and estimated V˙O2. Lastly, a Bland-Altman plot described the accuracy and precision of the estimated V˙O2 at each shuttle intensity. Results: Slopes and intercepts of the HR/V˙O2 appeared not different between FW and shuttle running. At 50%MAS, HR underestimated the V˙O2 (~7%), whereas returned accurate values at the two higher velocities, although with high variability (±18%). Conclusions: When using HR as V˙O2 indicator during shuttle running over short paths, a separated analysis of the HR validity as V˙O2 indicator is recommended especially when administering different exercise intensities.

Biceps Brachii and Brachioradialis Excitation in Biceps Curl Exercise: Different Handgrips, Different Synergy.

The current study analyzed the excitation of biceps brachii, brachioradialis, and anterior deltoid during bilateral biceps curl performed with different handgrips. Ten competitive bodybuilders performed bilateral biceps curl in non-exhaustive 6-rep sets using 8-RM with the forearm in supinated, pronated, and neutral positions. The ascending and descending phase of each variation was separately analyzed using the normalized root mean square collected using surface electromyography. During the ascending phase, (i) biceps brachii excitation was greater with the supinated compared to the pronated [+19(7)%, ES: 2.60] and neutral handgrip [+12(9)%, ES: 1.24], (ii) the brachioradialis showed greater excitation with the supinated compared to the pronated [+5(4)%, ES: 1.01] and neutral handgrip [+6(5)%, ES: 1.10], (iii) the anterior deltoid excitation was greater with the pronated and neutral handgrip compared to the supinated condition [+6(3)% and +9(2)%, ES: 2.07 and 3.18, respectively]. During the descending phase, the anterior deltoid showed greater excitation in the pronated compared to the supinated handgrip [+5(4)%, ES: 1.02]. Changing the handgrips when performing biceps curl induces specific variations in biceps brachii and brachioradialis excitation and requires different anterior deltoid interventions for stabilizing the humeral head. Practitioners should consider including different handgrips in the biceps curl routine to vary the neural and mechanical stimuli.

Bilateral Biceps Curl Shows Distinct Biceps Brachii and Anterior Deltoid Excitation Comparing Straight vs. EZ Barbell Coupled with Arms Flexion/No-Flexion.

The present study investigated the excitation of the biceps brachii and anterior deltoid during bilateral biceps curl performed using the straight vs. EZ barbell and with or without flexing the arms. Ten competitive bodybuilders performed bilateral biceps curl in non-exhaustive 6-rep sets using 8-RM in four variations: using the straight barbell flexing (STflex) or not flexing the arms (STno-flex) or the EZ barbell flexing (EZflex) or not flexing the arms (EZno-flex). The ascending and descending phases were separately analyzed using the normalized root mean square (nRMS) collected using surface electro-myography. For the biceps brachii, during the ascending phase, a greater nRMS was observed in STno-flex vs. EZno-flex (+1.8%, effect size [ES]: 0.74), in STflex vs. STno-flex (+17.7%, ES: 3.93) and in EZflex vs. EZno-flex (+20.3%, ES: 5.87). During the descending phase, a greater nRMS was observed in STflex vs. EZflex (+3.8%, ES: 1.15), in STno-flex vs. STflex (+2.8%, ES: 0.86) and in EZno-flex vs. EZflex (+8.1%, ES: 1.81). The anterior deltoid showed distinct excitation based on the arm flexion/no-flexion. A slight advantage in biceps brachii excitation appears when using the straight vs. EZ barbell. Flexing or not flexing the arms seems to uniquely excite the biceps brachii and anterior deltoid. Practitioners should consider including different bilateral biceps barbell curls in their routine to vary the neural and mechanical stimuli.

Is the Interpolated-Twitch Technique-Derived Voluntary Activation Just Neural? Novel Perspectives from Mechanomyographic Data.

PURPOSE: Voluntary activation (VA) determined by interpolation-twitch technique could be affected by the characteristics of the in-series elastic components. To overcome this possible bias, a novel approach based on the mechanomyographic (MMG) signal to detect voluntary activation (VA MMG ) has been proposed. We examined the changes in VA and VA MMG after passive stretching to check the influence of neural and mechanical factors in the force output. METHODS: Twenty-six healthy men underwent VA assessment using the interpolated-twitch technique before and after unilateral passive stretching of the plantarflexors (five 45-s on + 15-s off). In addition to the force signal, the MMG signal was detected on gastrocnemius medialis, gastrocnemius lateralis, and soleus. From the force and MMG signal analysis, VA and VA MMG were calculated in the stretched and contralateral nonstretched limbs. Joint passive stiffness was also defined. RESULTS: In the stretched limb, passive stretching increased dorsiflexion range (mean ± SD = +18% ± 10%, P < 0.001, ES = 1.54) but reduced joint passive stiffness (-22% ± 8%, P < 0.001, ES = -1.75), maximum voluntary contraction (-15% ± 7%, P < 0.001, ES = -0.87), VA (-7% ± 3%, P < 0.001, ES = -2.32), and VA MMG (~-5% ± 2%, P < 0.001, ES = -1.26/-1.14). In the contralateral nonstretched limb, passive stretching increased dorsiflexion range (+10% ± 6%, P < 0.001, ES = 0.80) but reduced joint passive stiffness (-3% ± 2%, P = 0.041, ES = -0.27), maximum voluntary contraction (-4% ± 3%, P = 0.035, ES = -0.24), VA (-4% ± 2%, P < 0.001, ES = -1.77), and VA MMG (~- 2% ± 1%, P < 0.05, ES = -0.54/-0.46). The stretch-induced changes in VA correlated with VA MMG ( R ranging from 0.447 to 0.583 considering all muscles) and with joint passive stiffness (stretched limb: R = 0.503; contralateral nonstretched limb: R = 0.530). CONCLUSIONS: VA output is overall influenced by both neural and mechanical factors, not distinguishable using the interpolated-twitch technique. VA MMG is a complementary index to assess the changes in VA not influenced by mechanical factors and to examine synergistic muscles.

Front vs Back and Barbell vs Machine Overhead Press: An Electromyographic Analysis and Implications For Resistance Training.

Overhead press is commonly performed to reinforce the muscles surrounding the shoulders. However, many overhead press variations can be executed, thus varying the stimuli to each muscle. Therefore, the current study compared the muscles excitation during overhead press performed with the barbell passing in front or behind the head or using a shoulder press machine. Eight competitive bodybuilders performed in random order front (front-BMP) or back barbell military press (back-BMP), and front (front-MSP) with neutral handgrip or back machine shoulder press (back-MSP). Normalized surface electromyographic root mean square (RMS) of anterior, medial and posterior deltoid, upper trapezius, pectoralis major and triceps brachii was recorded during both the ascending and descending phases. During the ascending phase, anterior deltoid showed greater RMS in back-BMP than back-MSP [ES: 1.42, (95% confidence interval 0.32/2.51)]. Medial deltoid showed greater RMS in back-BMP than front-BMP [ES: 3.68 (2.07/5.29)], and back-MSP [ES: 7.51 (4.73/10.29)]. Posterior deltoid showed greater RMS in back-BMP than front-BMP [ES: 9.00 (5.73/12.27)]. Pectoralis major showed greater RMS in front-BMP than back-BMP [ES: 3.11 (1.65-4.56)] and in front-MSP than back-MSP [ES: 20.52 (13.34/27.70)]. During the descending phase, anterior deltoid was more excited in back-BMP compared to front-BMP [ES: 7.66 (4.83/10.49). Medial deltoid showed greater RMS in back-BMP than front-BMP [ES: 4.56 (2.70/6.42)]. Posterior deltoid showed greater RMS in back-BMP than front-BMP [ES: 8.65 (5.50/11.80)]. Pectoralis major showed greater RMS in front-BMP than back-BMP [ES: 4.20 (2.44/5.95)]. No between-exercise difference was observed for upper trapezius. Performing back overhead press enhances the excitation of medial and posterior and partly anterior deltoid, while front overhead favors pectoralis major. Overhead press performed using barbell excites muscles more than using machine to stabilize the trajectory of the external load. Different variations of overhead press appear to provide different stimuli to the shoulder muscles and may be used accordingly during the training routine.

Determining voluntary activation in synergistic muscles: a novel mechanomyographic approach.

PURPOSE: Drawing on correlations between the mechanomyographic (MMG) and the force signal, we devised a novel approach based on MMG signal analysis to detect voluntary activation (VA) of the synergistic superficial heads of the quadriceps muscle. We hypothesized that, after a fatiguing exercise, the changes in the evoked MMG signal of each quadriceps head would correlate with the changes in the level of VA in the whole quadriceps. METHODS: Twenty-five men underwent a unilateral single-leg quadriceps exercise to failure. Before and after exercise, VA was assessed by interpolated-twitch-technique via nerve stimulation during and after maximum voluntary contraction (MVC). The force and MMG signal were recorded from vastus lateralis, vastus medialis, and rectus femoris. The MMG peak-to-peak was calculated and the voluntary activation index (VAMMG), defined as the superimposed/potentiated MMG peak-to-peak ratio, was determined from the MMG signal for each head. RESULTS: VAMMG presented a very high intraclass correlation coefficient (0.981-0.998) and sensitivity (MDC95%: 0.42-6.97%). MVC and VA were decreased after exercise in both the exercising [MVC:-17(5)%, ES -0.92; VA: -7(3)%, ES -1.90] and the contralateral limb [MVC: -9(4)%, ES -0.48; VA: -4(1)%, ES -1.51]. VAMMG was decreased in both the exercising [~ -9(6)%, ES -1.77] and contralateral limb [~ -3(2)%, ES -0.57], with a greater decrease in VAMMG noted only in the vastus medialis of the exercising limb. Moderate-to-very high correlations were found between VAMMG and VA (R-range: 0.503-0.886) before and after exercise. CONCLUSION: VAMMG may be implemented to assess VA and provide further information when multiple synergistic muscle heads are involved in fatiguing exercises.

Bilateral deficit magnitude increases with velocity during a half-squat exercise.

Movement velocity has been viewed as one of the bilateral deficit (BLD) determinants. This research tested the velocity effect on BLD during a half-squat exercise. The role of muscle excitation in BLD was also assessed. BLD amplitude was assessed in 12 male soccer players while performing a half-squat exercise with incremental load. During the exercise's pushing phase, the average force and velocity were measured in bilateral and unilateral conditions to provide the bilateral index (BI) at each interpolated velocity. The vastus lateralis and medialis excitation was assessed during the exercise by calculating the surface electromyography signal root mean square (sEMGRMS). The BI for sEMGRMS (sEMG BI) was calculated. The theoretical maximum force (F0) and velocity (v0) were also determined. F0 was +43 (28)% in bilateral compared with unilateral conditions (p < 0.001), whereas v0 was similar in both conditions (p = 0.386). The BI magnitude rose with the increase in velocity from -34 (7)% at 50%v0 to -70 (17)% at 90%v0 (p 0.03-<0.001), whereas no sEMG BI occurred (p: 0.07-0.991 in both muscles). The study reported velocity-dependent changes in the BLD amplitude, with the largest BLD amplitudes occurring at the highest velocities. This behaviour could provide useful information for setting specific contraction velocities to exploit/limit the BLD amplitude as a possible training stimulus.

An Electromyographic Analysis of Romanian, Step-Romanian, and Stiff-Leg Deadlift: Implication for Resistance Training.

The present study examined the posterior chain muscle excitation in different deadlift variations. Ten competitive bodybuilders (training seniority of 10.6 ± 1.8 years) performed the Romanian (RD), Romanian standing on a step (step-RD), and stiff-leg deadlift (SD) with an 80% 1-RM. The excitation of the gluteus maximus, gluteus medius, biceps femoris, semitendinosus, erector spinae longissimus, and iliocostalis was assessed during both the ascending and descending phases. During the ascending phase, the RMS of the gluteus maximus was greater in the step-RD than in the RD (effect size (ES): 1.70, 0.55/2.84) and SD (ES: 1.18, 0.11/2.24). Moreover, a greater RMS was found in the SD than in the RD (ES: 0.99, 0.04/1.95). The RMS of the semitendinosus was greater in the step-RD than in the RD (ES: 0.82, 0.20/1.44) and SD (ES: 3.13, 1.67/4.59). Moreover, a greater RMS was found in the RD than in the SD (ES: 1.38, 0.29/2.48). The RMS of the longissimus was greater in the step-RD than in the RD (ES: 2.12, 0.89/3.34) and SD (ES: 3.28, 1.78/4.78). The descending phase had fewer differences between the exercises. No further differences between the exercises were found. The step-RD increased the overall excitation of the posterior chain muscles, possibly because of the greater range of movement and posterior muscle elongation during the anterior flexion. Moreover, the RD appeared to target the semitendinosus more than the SD, while the latter excited the gluteus maximus more.

Long-Term Passive Leg Stretch Improves Systemic Vascular Responsiveness as Much as Single-Leg Exercise Training.

PURPOSE: The current study compared the local and systemic vascular responsiveness after small muscle mass endurance training or passive stretching training (PST). METHODS: Thirty-six sex-matched healthy participants underwent 8-wk single-leg knee extension (SLKE) (n = 12) training or PST (n = 12), or no intervention (control, n = 12). Before and after the intervention, local and systemic vascular responsiveness was assessed by Doppler ultrasound at the femoral (local effect) and brachial artery (systemic effect) during single passive leg movement and brachial flow-mediated dilation (FMD) test, respectively. RESULTS: After training, delta femoral blood flow (representing the local vascular responsiveness) increased after SLKE and PST by +54 (7)% (effect size, 2.72; P < 0.001) and +20 (2)% (effect size, 2.43; P < 0.001), respectively, albeit with a greater extent in SLKE (post-SLKE vs post-PST: +56 [8]% [effect size, 2.92; P < 0.001]). Interestingly, the %FMD (standing for the systemic effect) increased after SLKE and PST by +12 (2)% (effect size, 0.68; P < 0.001) and +11 (1)% (effect size, 0.83; P < 0.001), respectively, without any between-groups difference (P > 0.05). No changes occurred in control. CONCLUSIONS: The present findings revealed that both active and passive training modalities induced similar improvements in the brachial artery dilatation capacity, whereas the former was more effective in improving femoral artery blood flow. Passive stretching could be used in people with limited mobility to improve vascular responsiveness both at the local and systemic level and in this latter case has similar effects as small muscle mass endurance training.

Repeated Passive Mobilization to Stimulate Vascular Function in Individuals of Advanced Age Who Are Chronically Bedridden: A Randomized Controlled Trial.

BACKGROUND: Vascular dysfunction and associated disorders are major side effects of chronic bed rest, yet passive mobilization as a potential treatment has only been theorized so far. This study investigated the effects of passive mobilization treatment on vascular function in older, chronically bedridden people. METHOD: The study sample was 45 chronically bedridden people of advanced age (mean age: 87 years; 56% female; mean bed rest: 4 years) randomly assigned to a treatment (n = 23) or a control group (CTRL, n = 22). The treatment group received passive mobilization twice daily (30 minutes, 5 times/wk) for 4 weeks. A kinesiologist performed passive mobilization by passive knee flexion/extension at 1 Hz in one leg (treated leg [T-leg] vs control leg [Ctrl-leg]). The CTRL group received routine treatment. The primary outcome was changes in peak blood flow (∆peak) as measured with the single passive leg movement test at the common femoral artery. RESULTS: ∆Peak was increased in both legs in the Treatment group (+90.9 mL/min, p < .001, in T-leg and +25.7 mL/min, p = .039 in Ctrl-leg). No difference in peak blood flow after routine treatment was found in the CTRL group. CONCLUSION: Improvement in vascular function after 4 weeks of passive mobilization was recorded in the treatment group. Passive mobilization may be advantageously included in standard clinical practice as an effective strategy to treat vascular dysfunction in persons with severely limited mobility.

The Effects of Verbal Instructions on Lower Limb Muscles' Excitation in Back-Squat.

The present study investigated whether or not verbal instruction affects the electromyographic (EMG) amplitude of back-squat prime movers. Fifteen resistance-trained men performed back-squat at 50%1-RM and 80%1-RM and received external (EF) or internal focus (IF) on lower-limb posterior muscles. EMG amplitude of gluteus maximus, biceps femoris, gastrocnemius medialis, vastus lateralis, and tibialis anterior was recorded during both concentric and eccentric phases. During the concentric phase, the gluteus maximus and biceps femoris EMG amplitude was greater in IF vs EF at 50% [effect size (ES): 0.63 (95%CI 0.09/1.17) and 0.49 (0.10/0.78), respectively] and 80% [ES: 1.30 (0.29/2.21) and 0.59 (0.08/1.10)]. The gastrocnemius medialis EMG amplitude was greater in IF vs EF during the eccentric phase at 50% [ES: 0.73 (0.13/1.33)] and at 80% [ES: 0.72 (0.10/1.34)]. Concomitantly, vastus lateralis EMG amplitude was lower at 50% [ES: -0.71 (-1.38/-0.04)] and 80% [ES: -0.68 (-1.33/-0.03)]. During the eccentric phase, the tibialis anterior EMG amplitude was greater in IF vs EF at 50% [ES: 0.90 (0.12 to 1.68)] and 80% [ES: 0.74 (0.13/1.45)]. Irrespective of the load, in the thigh muscles the internal focus promoted a different motor pattern, increasing the hip extensors and reducing the knee extensor excitation during the concentric phase. Concomitantly, both ankle muscles were more excited during the eccentric phase, possibly to increase the anterior-posterior balance control. The internal focus in back-squat seems to have phase-dependent effects, and it is visible at both moderate and high loads.

Passive stretching decreases muscle efficiency in balance tasks.

The current study aimed to verify whether or not passive static stretching affects balance control capacity. Thirty-eight participants (19 women and 19 men) underwent a passive static stretching session, involving the knee extensor/flexor and dorsi/plantarflexor muscles, and a control session (no stretching, CTRL). Before (PRE), immediately after (POST), after 15 (POST15) and 30 min (POST30) from stretching (or rest in CTRL), balance control was evaluated under static and dynamic conditions, with open/closed eyes, and with/without somatosensory perturbation (foam under the feet). During tests, centre of pressure (CoP) sway area and perimeter and antero-posterior and medio-lateral sway mean speed were computed. Surface electromyography root mean square (sEMG RMS) was calculated from the vastus lateralis, biceps femoris, gastrocnemius medialis, and tibialis anterior muscles during MVC and during the balance tests. Hip flexion/extension and dorsi/plantarflexion range of motion (ROM), maximum voluntary contraction (MVC) and sEMG RMS during MVC were measured at the same time points. After stretching, ROM increased (≈6.5%; P<0.05), while MVC and sEMG RMS decreased (≈9% and ≈7.5%, respectively; P<0.05). Regardless of the testing condition, CoP sway area and the perimeter remained similar, while antero-posterior and medio-lateral sway mean speed decreased by ≈8% and ≈12%, respectively (P<0.05). sEMG RMS during the balance tests increased in all muscles in POST (≈7%, P<0.05). All variables recovered in POST30. No changes occurred in CTRL. Passive static stretching did not affect the overall balance control ability. However, greater muscle activation was required to maintain similar CoP sway, thus suggesting a decrease in muscle efficiency.

Effects of Power and Ballistic Training on Table Tennis Players' Electromyography Changes.

The aim of the present study was to analyze the effects of ballistic and power training on table tennis players' electromyography (EMG) changes. Thirty male table tennis players, who were able to perform top spin strikes properly, were randomly assigned to three groups: power training (PT; n = 10); ballistic training (BT; n = 10); and no training (CON = control group; n = 10). PT and BT were performed 3 times weekly for 8 weeks. Before and after training programs, a one-repetition maximum test (1RM) and the EMG activity of all the subjects' upper/lower body muscles while performing top spin strokes were analyzed. After training, significant interactions (group × time) were observed in increasing 1RM strength in upper/lower muscles (p < 0.05). However, neither training type had any significant effect on muscle EMG activity. These findings suggest that there should not necessarily be any significant change in the EMG signal after BT and PT despite the increase in muscle strength.

Effects of Shift Work in a Sample of Italian Nurses: Analysis of Rest-Activity Circadian Rhythm.

Shift work can lead to circadian desynchronization due to temporary misalignment between working hours and physiological and behavioral functioning, resulting in compromised health, insomnia, worsening of sleep quality, reduced ability to work during waking hours, and increased cardiovascular risk. We evaluated the effects of shift work on the rest-activity circadian rhythm (RAR) and health status of Italian orthopaedic nurses. The study population was 59 nurses: 44 worked the night shift and 15 worked the day shift. All carried out continuous 5-day actigraphic monitoring to assess RAR, including both the working and the rest period. The rhythmometric analysis showed that, during the working period, the night shift nurses had a significantly lower amplitude than the day shift nurses (p < 0.001), and the acrophase was significantly different between the two groups (p < 0.01). When we stratified the two groups by median body mass index (<25 kg/m2 normal weight and ≥25 kg/m2 overweight), during the working period, we noted a significantly lower amplitude for both the normal weight and the overweight nurses who worked the night shift (p < 0.01 and p < 0.001, normal weight and overweight respectively). The current findings suggest the need for further study of the relationship between activity levels and shift work.

Training status affects between-protocols differences in the assessment of maximal aerobic velocity.

PURPOSE: Continuous incremental protocols (CP) may misestimate the maximum aerobic velocity (Vmax) due to increases in running speed faster than cardiorespiratory/metabolic adjustments. A higher aerobic capacity may mitigate this issue due to faster pulmonary oxygen uptake ([Formula: see text]O2) kinetics. Therefore, this study aimed to compare three different protocols to assess Vmax in athletes with higher or lower training status. METHODS: Sixteen well-trained runners were classified according to higher (HI) or lower (LO) [Formula: see text]O2max [Formula: see text]O2-kinetics was calculated across four 5-min running bouts at 10 km·h-1. Two CPs [1 km·h-1 per min (CP1) and 1 km·h-1 every 2-min (CP2)] were performed to determine Vmax [Formula: see text]O2max, lactate-threshold and submaximal [Formula: see text]O2/velocity relationship. Results were compared to the discontinuous incremental protocol (DP). RESULTS: Vmax, [Formula: see text]O2max, [Formula: see text]CO2 and VE were higher [(P < 0.05,(ES:0.22/2.59)] in HI than in LO. [Formula: see text]O2-kinetics was faster [P < 0.05,(ES:-2.74/ - 1.76)] in HI than in LO. [Formula: see text]O2/velocity slope was lower in HI than in LO [(P < 0.05,(ES:-1.63/ - 0.18)]. Vmax and [Formula: see text]O2/velocity slope were CP1 > CP2 = DP for HI and CP1 > CP2 > DP for LO. A lower [P < 0.05,(ES:0.53/0.75)] Vmax-difference for both CP1 and CP2 vs DP was found in HI than in LO. Vmax-differences in CP1 vs DP showed a large inverse correlation with Vmax, [Formula: see text]O2max and lactate-threshold and a very large correlation with [Formula: see text]O2-kinetics. CONCLUSIONS: Higher aerobic training status witnessed by faster [Formula: see text]O2 kinetics led to lower between-protocol Vmax differences, particularly between CP2 vs DP. Faster kinetics may minimize the mismatch issues between metabolic and mechanical power that may occur in CP. This should be considered for exercise prescription at different percentages of Vmax.

Neuromuscular Correlates of the Contralateral Stretch-induced Strength Loss.

PURPOSE: The current study investigated the effects of unilateral passive stretching on the neuromuscular mechanisms involved in the force-generating capacity of the contralateral muscle. METHODS: Twenty-six healthy men underwent unilateral passive stretching of the plantarflexors (5 × 45 s on + 15 s off; total stretching time, 225 s). Before and after the stretching protocol, contralateral ankle range of motion, maximum voluntary contraction (MVC) of the plantarflexors, and surface electromyographic root-mean-square (sEMG RMS) of the soleus and the gastrocnemii muscles were determined. Concurrently, V-wave, maximum and superimposed H-reflex, and M-wave were elicited via nerve stimulation to estimate the supraspinal, spinal, and peripheral mechanisms, respectively. sEMG RMS, V-wave, and H-reflex were normalized to the M-wave. RESULTS: After passive stretching, contralateral ankle range of motion was increased (+8% [1%/15%], effect size [ES] = 0.43 [0.02/0.84], P < 0.001), MVC of the plantarflexors was decreased (-9% [-21%/-2%], ES = -0.96 [-1.53/-0.38], P < 0.001), and the sEMG RMS/M-wave of the soleus and the gastrocnemii muscles was decreased (≈-9%, ES ≈ -0.33, P < 0.05). Concurrently, the V-wave/M-wave superimposed was decreased in all muscles (≈-13%, ES = -0.81 to -0.52, P < 0.05). No change in H-reflex/M-wave and M-wave was observed under both maximum and superimposed condition. The decrease in the MVC and the sEMG RMS of the contralateral muscle was accompanied by a decrease in the V-wave/M-wave but not the H-reflex/M-wave ratios and the M-wave. CONCLUSIONS: The present outcomes suggest that only supraspinal mechanisms might be involved in the contralateral decrease in the maximum force-generating capacity.