Reproducibility of knee extensor and flexor contraction velocity in healthy men and women assessed using tensiomyography: A study protocol

Tensiomyography measures the radial displacement of a muscle during an electrically evoked twitch contraction. The rate of muscle displacement is increasingly reported to assess contractile properties. Several formulas currently exist to calculate the rate of displacement during the contraction phase of the maximal twitch response. However, information on the reproducibility of these formulas is scarce. Further, different rest intervals ranging from 10 s to 30 s are applied between consecutive stimuli during progressive electrical stimulation until the maximum twitch response. The effect of different rest intervals on the rate of displacement has not been investigated so far. The first aim of this study is to investigate the within and between-day reliability of the most frequently used formulas to calculate the rate of displacement. The second aim is to investigate the effect of changing the inter-stimulus interval on the rate of displacement. We will determine the rectus femoris and biceps femoris rate of displacement of twenty-four healthy subjects’ dominant leg on two consecutive days. The maximum displacement curve will be determined two times within three minutes on the first day and a third time 24 h later. On day two, we will also apply three blocks of ten consecutive stimuli at a constant intensity of 50 mA. Inter-stimuli intervals will be 10 s, 20 s or 30 s in each block, respectively, and three minutes between blocks. The order of inter-stimulus intervals will be randomized. This study will allow a direct comparison between the five most frequently used formulas to calculate the rate of displacement in terms of their reproducibility. Our data will also inform on the effect of different inter-stimulus intervals on the rate of displacement. These results will provide helpful information on methodical considerations to determine the rate of displacement and may thus contribute to a standardized approach.

Influence of Counter Movement Jump Session with Different Rest Intervals on Muscle Damage and Soreness

Objectives: Plyometrics has been used in sports training and many aspects of this modality are poorly understood. This study measures the magnitude of variations of serum creatine kinase (CK) activity and perceived muscle soreness after one session of Countermovement Jump (CMJ) session and compares 1 and 3 minutes rest intervals between each sets.Methods: A group of 30 young male was dividing in two groups and performed ten sets of ten CMJ with 1 or 3 minutes rest interval between sets. Before and after session (24, 48, and 72-h) they informed the muscle soreness perception and blood samples were collected for dosage of serum CK activity. Two (time) x Two (treatment) ANOVA was used to test differences in serum CK activity and muscle soreness. The alpha level was set at 0.05.Results: Serum CK activity measured 48 h after session augments ~2 and ~1.5 times in 1 min and 3 min rest interval respectively. No significant difference between groups that rests 1 or 3 minutes between sets was found. Muscle soreness rises 24 h after session without significant differences between groups.Conclusions: The findings show that the CMJ increases perceived muscle soreness and increases the serum CK activity, and the intervals of rest do not modulate these variables.

Near-infrared spectroscopy during low-intensity blood flow restriction resistance exercise

Introduction: Low-intensity resistance exercises with blood flow restriction are known to be effective in promoting muscular strength and hypertrophy; however, there is a paucity of evidence on their acute hemodynamic responses. Objective: To compare the changes in muscular oxyhemoglobin (O2Hb), deoxyhemoglobin (HHb) concentrations, and O2 saturation (StO2) during low load exercise under free blood flow (FreeBF) and blood flow restriction (BFR). Methods: Fifteen healthy males were subjected to bilateral knee extension tests under FreeBF and BFR conditions, in a random order. The knee extension exercise included four sets of 15 repetitions at 20% of one-repetition maximum, with 30s interval between the sets. In the BFR condition, subjects exercised with a cuff positioned on the proximal thigh and inflated to 50% of total occlusion pressure. Changes in the O2Hb, HHb, total hemoglobin (tHb), and StO2 in vastus lateralis muscle were monitored using near-infrared spectroscopy. Results: A two-way repeated-measures ANOVA revealed significant main effects for sets for all variables (P < 0.05). Moreover, the values in StO2 during sets 2, 3, and 4 in BFR conditions were significantly lower than those in freeBF. Significant differences were also seen between the exercise conditions during rest intervals for HHb (rest intervals 2, 3, and 4) and tHb (rest interval 3; P < 0.05). There were no significant interactions between conditions and sets or conditions and intervals for O2Hb. Conclusion: Low-intensity resistance exercise performed with BFR significantly decreased the acute muscle StO2 and increased total muscle hemoglobin.

Effects of Introducing Rest Intervals in Functional Fitness Training

Background: Functional Fitness Training (FFT) is a new exercise modality prioritizing functional multi-joint movements executed at high intensity as a circuit. Objective: To examine the impacts of introducing rest intervals in a FFT workout compared to “rounds for time” (RFT) FFT. Materials and Methods: Participants were 25 resistance-trained adults who completed two FFT workouts 1 week apart. The study design was crossover such that in a given session half the participants completed the standard and the other half the adapted FFT (FFTadapted). The workouts consisted of the same exercises (circuit of four rounds of exercises), but one (FFTadapted) included preset rest intervals (three sets of 1 min after each completed round). Before and after the workouts, countermovement jump ability and blood lactate were measured. Heart rate (HR) and ratings of perceived exertion (RPE) were measured post-exercise. Results: For both the standard and adapted protocols, mean HR was 90% age-predicted maximum. Final RPE was also similar for both workouts (~15–15.5) and indicated a “hard” work intensity. Both FFTs took the same time to complete (~13 min). Furthermore, no significant differences were observed in jump ability between FFTs. In contrast, lactate (15.11 ± 3.64 vs. 13.48 ± 3.64 mmol·L−1, p < 0.05), measured 3 min post-exercise, was significantly lower in FFTadapted. Conclusions: In FFTadapted, there was a significant reduction in RPE and blood lactate concentrations after exercise, while there were no significant differences in either HR or jumping ability, compared to a FFT workout in RFT methodology.

Rest Intervals during Virtual Reality Gaming Augments Standing Postural Sway Disturbance

Immersive virtual reality (VR) can cause acute sickness, visual disturbance, and balance impairment. Some manufacturers recommend intermittent breaks to overcome these issues; however, limited evidence examining whether this is beneficial exists. The aim of this study was to examine whether taking breaks during VR gaming reduced its effect on postural sway during standing balance assessments. Twenty-five people participated in this crossover design study, performing 50 min of VR gaming either continuously or with intermittent 10 min exposure/rest intervals. Standing eyes open, two-legged balance assessments were performed immediately pre-, immediately post- and 40 min post-exposure. The primary outcome measure was total path length; secondary measures included independent axis path velocity, amplitude, standard deviation, discrete and continuous wavelet transform-derived variables, and detrended fluctuation analysis. Total path length was significantly (p < 0.05) reduced immediately post-VR gaming exposure in the intermittent rest break group both in comparison to within-condition baseline values and between-condition timepoint results. Conversely, it remained consistent across timepoints in the continuous exposure group. These changes consisted of a more clustered movement speed pattern about a lower central frequency, evidenced by signal frequency content. These findings indicate that caution is required before recommending rest breaks during VR exposure until we know more about how balance and falls risk are affected.

The Effects of Plyometric Conditioning Exercises on Volleyball Performance with Self-Selected Rest Intervals

Post-activation performance enhancement remains a topic of debate in sport science. The purpose of this study was to examine the effects of lower-body plyometric conditioning activity (CA) with a self-selected intra-complex rest interval on upper and lower-body volleyball specific performance. Eleven resistance-trained female volleyball players participated in the study (age: 20 ± 2 years; body mass: 67.8 ± 4.4 kg; height: 178 ± 6 cm; half back squat one-repetition maximum: 78.6 ± 10.2 kg; experience in resistance training: 5.5 ± 2.1 years and in volleyball training: 10 ± 2.3 years). Each participant performed a plyometric CA followed by two different sport-specific tests: an attack jump and a standing spike attack. The changes in jump height (JH), relative mean power output (MP) and ball velocity (BV) were analyzed before and after the CA with self-selected rest intervals. The applied plyometric CA with self-selected intra-complex rest intervals led to an insignificant decline in JH (p = 0.594; effect size [ES]: −0.27) and MP (p = 0.328; ES: −0.46) obtained during the attack jump as well as a significant decline in BV (p = 0.029; ES: −0.72) during the standing spike attack. This study showed that a plyometric CA with self-selected intra-complex rest intervals failed to elicit localized and non-localized PAPE effect in a group of sub-elite volleyball players.