Neuromechanical Differences between Pronated and Supinated Forearm Positions during Upper-Body Wingate Tests.

Arm-cycling is a versatile exercise modality with applications in both athletic enhancement and rehabilitation, yet the influence of forearm orientation remains understudied. Thus, this study aimed to investigate the impact of forearm position on upper-body arm-cycling Wingate tests. Fourteen adult males (27.3 ± 5.8 years) underwent bilateral assessments of handgrip strength in standing and seated positions, followed by pronated and supinated forward arm-cycling Wingate tests. Electromyography (EMG) was recorded from five upper-extremity muscles, including anterior deltoid, triceps brachii lateral head, biceps brachii, latissimus dorsi, and brachioradialis. Simultaneously, bilateral normal and propulsion forces were measured at the pedal-crank interface. Rate of perceived exertion (RPE), power output, and fatigue index were recorded post-test. The results showed that a pronated forearm position provided significantly (p < 0.05) higher normal and propulsion forces and triceps brachii muscle activation patterns during arm-cycling. No significant difference in RPE was observed between forearm positions (p = 0.17). A positive correlation was found between seated handgrip strength and peak power output during the Wingate test while pronated (dominant: p = 0.01, r = 0.55; non-dominant: p = 0.03, r = 0.49) and supinated (dominant: p = 0.03, r = 0.51; don-dominant: p = 0.04, r = 0.47). Fatigue changed the force and EMG profile during the Wingate test. In conclusion, this study enhances our understanding of forearm position's impact on upper-body Wingate tests. These findings have implications for optimizing training and performance strategies in individuals using arm-cycling for athletic enhancement and rehabilitation.

Endurance-exercise training adaptations in spinal motoneurones: potential functional relevance to locomotor output and assessment in humans.

It is clear from non-human animal work that spinal motoneurones undergo endurance training (chronic) and locomotor (acute) related changes in their electrical properties and thus their ability to fire action potentials in response to synaptic input. The functional implications of these changes, however, are speculative. In humans, data suggests that similar chronic and acute changes in motoneurone excitability may occur, though the work is limited due to technical constraints. To examine the potential influence of chronic changes in human motoneurone excitability on the acute changes that occur during locomotor output, we must develop more sophisticated recording techniques or adapt our current methods. In this review, we briefly discuss chronic and acute changes in motoneurone excitability arising from non-human and human work. We then discuss the potential interaction effects of chronic and acute changes in motoneurone excitability and the potential impact on locomotor output. Finally, we discuss the use of high-density surface electromyogram recordings to examine human motor unit firing patterns and thus, indirectly, motoneurone excitability. The assessment of single motor units from high-density recording is mainly limited to tonic motor outputs and minimally dynamic motor output such as postural sway. Adapting this technology for use during locomotor outputs would allow us to gain a better understanding of the potential functional implications of endurance training-induced changes in human motoneurone excitability on motor output.

Moving forward: methodological considerations for assessing corticospinal excitability during rhythmic motor output in humans.

The use of transcranial magnetic stimulation to assess the excitability of the central nervous system to further understand the neural control of human movement is expansive. The majority of the work performed to-date has assessed corticospinal excitability either at rest or during relatively simple isometric contractions. The results from this work are not easily extrapolated to rhythmic, dynamic motor outputs, given that corticospinal excitability is task-, phase-, intensity-, direction-, and muscle-dependent (Power KE, Lockyer EJ, Forman DA, Button DC. Appl Physiol Nutr Metab 43: 1176-1185, 2018). Assessing corticospinal excitability during rhythmic motor output, however, involves technical challenges that are to be overcome, or at the minimum considered, when attempting to design experiments and interpret the physiological relevance of the results. The purpose of this narrative review is to highlight the research examining corticospinal excitability during a rhythmic motor output and, importantly, to provide recommendations regarding the many factors that must be considered when designing and interpreting findings from studies that involve limb movement. To do so, the majority of work described herein refers to work performed using arm cycling (arm pedaling or arm cranking) as a model of a rhythmic motor output used to examine the neural control of human locomotion.

Short-interval intracortical inhibition of the biceps brachii in chronic-resistance versus non-resistance-trained individuals.

The purpose of this study was to investigate the effects of chronic resistance training on corticospinal excitability and short intracortical inhibition of the biceps brachii. Eight chronic resistance-trained (RT) and eight non-RT participants completed one experimental session including a total of 30 brief (7 s) elbow flexors isometric contractions at various force outputs [15, 25 and 40% of maximum voluntary contraction (MVC)]. Before the contractions, MVC, maximal compound muscle action potential (Mmax) during 5% MVC and active motor threshold (AMT) at the three various force outputs were recorded. MVC force of the chronic-RT group was 24% higher than the non-RT group (p ≤ 0.001; ω2 = 0.72). The chronic-RT group had lower AMTs at targeted forces of 15 and 25% MVC (p = 0.022 and p = 0.012, respectively) compared to the non-RT group. During 25 and 40% of MVC, the non-RT group exhibited decreased SICI in comparison to the chronic-RT group (p = 0.008; ω2 = 0.35 and p = 0.03; ω2 = 0.21, respectively). However, SICI did not differ between groups at 15% MVC (p = 0.62). In conclusion, chronic resistance training significantly reduces SICI. This suggests the presence of an adaptive process of inhibitory and facilitatory network activation, which may cancel out the SICI, allowing for increased corticomotor drive to the exercised muscle following a long period of resistance training.

Effects of roller massager on muscle recovery after exercise-induced muscle damage.

Two experiments (n = 10) were conducted to determine the effects of roller massager (RM) on ankle plantar flexor muscle recovery after exercise-induced muscle damage (EIMD). Experiment 1 examined both functional [i.e., ankle plantar flexion maximal isometric contraction and submaximal (30%) sustained force; ankle dorsiflexion maximal range of motion and resistance to stretch; and medial gastrocnemius pain pressure threshold] and morphological [cross-sectional area, thickness, fascicle length, and fascicle angle] variables, before and immediately, 1, 24, 48, and 72 h after an EIMD stimulus. Experiment 2 examined medial gastrocnemius deoxyhaemoglobin concentration kinetics before and 48 h after EIMD. Participants performed both experiments twice: with (RM) and without (no-roller massager; NRM) the application of a RM (6 × 45 s; 20-s rest between sets). RM intervention did not alter the functional impairment after EIMD, as well as the medial gastrocnemius morphology and oxygenation kinetics (P > 0.05). Although, an acute increase of ipsilateral (RM = + 19%, NRM = -5%, P = 0.032) and a strong tendency for contralateral (P = 0.095) medial gastrocnemius pain pressure threshold were observed. The present results suggest that a RM has no effect on plantar flexors performance, morphology, and oxygenation recovery after EIMD, except for muscle pain pressure threshold (i.e., a soreness).

Corticospinal excitability of the biceps brachii is shoulder position dependent.

The purpose of this study was to examine the effect of shoulder position on corticospinal excitability (CSE) of the biceps brachii during rest and a 10% maximal voluntary contraction (MVC). Participants (n = 9) completed two experimental sessions with four conditions: 1) rest, 0° shoulder flexion; 2) 10% MVC, 0° shoulder flexion; 3) rest, 90° shoulder flexion; and 4) 10% MVC, 90° shoulder flexion. Transcranial magnetic, transmastoid electrical, and Erb's point stimulation were used to induce motor-evoked potentials (MEPs), cervicomedullary MEPs (CMEPs), and maximal muscle compound potentials (Mmax), respectively, in the biceps brachii in each condition. At rest, MEP, CMEP, and Mmax amplitudes increased (P < 0.01) by 509.7 ± 118.3%, 113.3 ± 28.3%, and 155.1 ± 47.9%, respectively, at 90° compared with 0°. At 10% MVC, MEP amplitudes did not differ (P = 0.08), but CMEP and Mmax amplitudes increased (P < 0.05) by 32.3 ± 10.5% and 127.9 ± 26.1%, respectively, at 90° compared with 0°. MEP/Mmax increased (P < 0.01) by 224.0 ± 99.1% at rest and decreased (P < 0.05) by 51.3 ± 6.7% at 10% MVC at 90° compared with 0°. CMEP/Mmax was not different (P = 0.22) at rest but decreased (P < 0.01) at 10% MVC by 33.6 ± 6.1% at 90° compared with 0°. EMG increased (P < 0.001) by 8.3 ± 2.0% at rest and decreased (P < 0.001) by 21.4 ± 4.4% at 10% MVC at 90° compared with 0°. In conclusion, CSE of the biceps brachii was dependent on shoulder position, and the pattern of change was altered within the state in which it was measured. The position-dependent changes in Mmax amplitude, EMG, and CSE itself all contribute to the overall change in CSE of the biceps brachii.NEW & NOTEWORTHY We demonstrate that when the shoulder is placed into two common positions for determining elbow flexor force and activation, corticospinal excitability (CSE) of the biceps brachii is both shoulder position and state dependent. At rest, when the shoulder is flexed from 0° to 90°, supraspinal factors predominantly alter CSE, whereas during a slight contraction, spinal factors predominantly alter CSE. Finally, the normalization techniques frequently used by researchers to investigate CSE may under- and overestimate CSE when shoulder position is changed.

Differences in corticospinal excitability to the biceps brachii between arm cycling and tonic contraction are not evident at the immediate onset of movement.

This is the first study to examine changes in corticospinal excitability to the biceps brachii during the onset of arm cycling from a resting position to a point when steady-state arm cycling was obtained. Supraspinal and spinal excitability were assessed using motor-evoked potentials (MEPs) elicited via transcranial magnetic stimulation and cervicomedullary evoked potentials (CMEPs) elicited via transmastoid electrical stimulation, respectively. Evoked responses were recorded from the biceps brachii during elbow flexion (6 o'clock relative to a clock face) for both arm cycling and an intensity-matched tonic contraction at three separate periods: (1) immediately at the onset of motor output and after completion of the (2) 4th revolution and (3) 9th revolution. There was no difference during initiation between tasks for MEP (P = 0.79) or CMEP amplitudes (P = 0.57). However, MEP amplitudes were significantly larger during arm cycling than an intensity-matched tonic contraction after the completion of the 4th (Cycling 76.48 ± 17.35 % of M max, Tonic 63.45 ± 18.45 % of M max, P < 0.05) and 9th revolutions (Cycling 72.37 ± 15.96 % of M max, Tonic 58.1 ± 24.23 % of M max, P < 0.05). There were no differences between conditions in CMEP amplitudes at the 4th (Cycling 49.6 ± 25.4 % of M max, Tonic 41.6 ± 11.2 % of M max, P = 0.31) or the 9th revolution (Cycling 47.2 ± 17.0 % of M max, Tonic 40.8 ± 13.6 % of M max, P = 0.29). These results demonstrate that corticospinal excitability is not different between arm cycling and a tonic contraction at motor output onset, but supraspinal excitability is enhanced during steady-state arm cycling. This suggests a similarity in the way the corticospinal tract initiates motor outputs in humans, regardless of the differences that present themselves in the later, steady-state stages.

Effect of an Ankle Compression Garment on Fatigue and Performance.

The aim of this study was to examine the effects of an ankle compression garment (CG) on muscle performance and physiological variables associated with recovery from fatigue. Fifteen participants took part in a randomized crossover study design with 2 experimental conditions (ankle CG and control). The dependent variables skin temperature, evoked muscle contractile properties, maximal voluntary contraction (MVC) force, electromyography (EMG), drop jump performance (20, 35, and 50 cm box heights), continuous drop jump (30 cm), time to fatigue (TTF), and blood lactate concentration were measured pre- and post-warm-up and postfatigue. Compared with control condition, ankle CG condition had significantly reduced half-relaxation times (p = 0.043) and higher skin temperatures at post-warm-up and post-fatigue protocol (p < 0.001, Δ3.2 and Δ4%, respectively). Participants also exhibited significantly lower ground reaction forces (GRFs) for 50-cm drop jumps (p = 0.044, Δ9.9%) with ankle CG at post-warm-up. There were no significant differences between conditions for muscle contractile properties, MVC force or EMG, jump height, take-off velocity, contact time, and jumping TTF. Independent of group, there was a threefold increase in blood lactate (p < 0.01) from pre-warm-up to post-fatigue and a significant decrease in MVC force (p = 0.048, Δ8.1%) from post-warm-up to postfatigue. Results suggest that ankle CG increased and maintained skin temperature during recovery, decreased twitch half-relaxation times, and reduced GRF from a 50-cm drop height. However, ankle CG did not improve other performance measures, aid in recovery, or affect blood lactate clearance.

Cadence-dependent changes in corticospinal excitability of the biceps brachii during arm cycling.

This is the first study to report the influence of different cadences on the modulation of supraspinal and spinal excitability during arm cycling. Supraspinal and spinal excitability were assessed using transcranial magnetic stimulation of the motor cortex and transmastoid electrical stimulation of the corticospinal tract, respectively. Transcranial magnetic stimulation-induced motor evoked potentials and transmastoid electrical stimulation-induced cervicomedullary evoked potentials (CMEPs) were recorded from the biceps brachii at two separate positions corresponding to elbow flexion and extension (6 and 12 o'clock relative to a clock face, respectively) while arm cycling at 30, 60 and 90 rpm. Motor evoked potential amplitudes increased significantly as cadence increased during both elbow flexion (P < 0.001) and extension (P = 0.027). CMEP amplitudes also increased with cadence during elbow flexion (P < 0.01); however, the opposite occurred during elbow extension (i.e., decreased CMEP amplitude; P = 0.01). The data indicate an overall increase in the excitability of corticospinal neurons which ultimately project to biceps brachii throughout arm cycling as cadence increased. Conversely, changes in spinal excitability as cadence increased were phase dependent (i.e., increased during elbow flexion and decreased during elbow extension). Phase- and cadence-dependent changes in spinal excitability are suggested to be mediated via changes in the balance of excitatory and inhibitory synaptic input to the motor pool, as opposed to changes in the intrinsic properties of spinal motoneurons.

Neuromuscular fatigue of the knee extensors during repeated maximal intensity intermittent-sprints on a cycle ergometer.

INTRODUCTION: We studied the time course of neuromuscular fatigue during maximal intensity intermittent-sprint cycling. METHODS: Eight participants completed 10, 10-s sprints interspersed with 180 s of recovery. The power outputs were recorded for each sprint. Knee extensor maximum voluntary contraction (MVC) force, voluntary activation, and evoked contractile properties were recorded presprint, postsprint 5, and postsprint 10. RESULTS: Total work over the 10 sprints decreased significantly (P < 0.05) and could be described by 2 linear relationships from sprints 1-5 compared with sprints 6-10. Participants had significantly (P < 0.05) lower MVC and twitch forces postsprint 5 compared with presprint. MVC, voluntary activation, and twitch force were decreased (P < 0.05) postsprint 10 compared with postsprint 5. CONCLUSIONS: The maximal intermittent sprints induced neuromuscular fatigue. Neuromuscular fatigue in the first 5 sprints was mainly peripheral, whereas in the last 5 sprints it was both peripheral and central.

Pain pressure threshold of a muscle tender spot increases following local and non-local rolling massage.

BACKGROUND: The aim of the present study was to determine the acute effect of rolling massage on pressure pain threshold (PPT) in individuals with tender spots in their plantar flexor muscles. METHODS: In a randomized control trial and single blinded study, tender spots were identified in 150 participants' plantar flexor muscles (gastrocnemius or soleus). Then participants were randomly assigned to one of five intervention groups (n = 30): 1) heavy rolling massage on the calf that exhibited the higher tenderness (Ipsi-R), 2) heavy rolling massage on the contralateral calf (Contra-R), 3) light stroking of the skin with roller massager on the calf that exhibited the higher tenderness (Sham), 4) manual massage on the calf that exhibited the higher tenderness (Ipsi-M) and 5) no intervention (Control). PPT was measured at 30 s and up to 15 min post-intervention via a pressure algometer. RESULTS: At 30 s post-intervention, the Ipsi-R (24 %) and Contra-R (21 %) demonstrated higher (p < 0.03) PPT values compared with Control and Sham. During 15 min post-intervention, PPT was higher (p < 0.05) following Ipsi-R (19.2 %), Contra-R (15.9 %) and Ipsi-M (10.9 %) compared with Control. There was no difference between the effects of three deep tissue massages (Ipsi-R, Ipsi-M and Contra-R) on PPT. DISCUSSION: Whereas the increased PPT following ipsilateral massage (Ipsi-R and Ipsi-M) might be attributed to the release of fibrous adhesions; the non-localized effect of rolling massage on the contralateral limb suggests that other mechanisms such as a central pain-modulatory system play a role in mediation of perceived pain following brief tissue massage. CONCLUSION: Overall, rolling massage over a tender spot reduces pain perception. TRIAL REGISTRATION: ClinicalTrials.gov ( NCT02528812 ), August 19(th), 2015.

Simulated motion negatively affects motor task but not neuromuscular performance.

The effects of long duration simulated motion on motor task and neuromuscular performance along with time frames required to recover from these effects are relatively unknown. This study aimed to determine (1) how simulated motion affects motor task and neuromuscular performance over one hour of motion and (2) the time course of recovery from any decrements. The dependent variables that were measured included: reaction time; visuomotor accuracy tracking; maximal voluntary contractions; voluntary activation; evoked contractile properties and biceps brachii electromyography of the elbow flexors. Reaction times and error rates of the visuomotor accuracy tracking task were compromised in motion, but maximal force, voluntary activation, evoked contractile properties and rmsEMG responses of the biceps brachii were unaffected by motion. It is concluded that motion causes an increase in attention demands, which have a greater effect on motor task rather than neuromuscular performance. PRACTITIONER SUMMARY: Minor delays or mistakes can separate life and death at sea. The safety and productivity of most vessels rely on error-free performance of motor tasks. This study demonstrates that human ability to perform motor tasks is compromised by ship motions and may aid in developing training and safety guidelines for seafarers.

Corticospinal excitability of the biceps brachii is higher during arm cycling than an intensity-matched tonic contraction.

Human studies have not assessed corticospinal excitability of an upper-limb prime mover during arm cycling. The purpose of the present study was to determine whether supraspinal and/or spinal motoneuron excitability of the biceps brachii was different between arm cycling and an intensity-matched tonic contraction. We hypothesized that spinal motoneuron excitability would be higher during arm cycling than an intensity-matched tonic contraction. Supraspinal and spinal motoneuron excitability were assessed using transcranial magnetic stimulation (TMS) of the motor cortex and transmastoid electrical stimulation (TMES) of the corticospinal tract, respectively. TMS-induced motor-evoked potentials (MEPs) and TMES-induced cervicomedullary-evoked potentials (CMEPs) were assessed at three separate positions (3, 6, and 12 o'clock relative to a clock face) during arm cycling and an intensity-matched tonic contraction. MEP amplitudes were 7.2 and 8.8% maximum amplitude of the compound muscle action potential (Mmax) larger during arm cycling compared with a tonic contraction at the 3 (P < 0.001) and 6 o'clock (P < 0.001) positions, respectively. There was no difference between tasks during elbow extension (12 o'clock). CMEP amplitudes were 5.2% Mmax larger during arm cycling compared with a tonic contraction at the 3 o'clock position (P < 0.001) with no differences seen at midflexion (6 o'clock) or extension (12 o'clock). The data indicate an increase in the excitability of corticospinal neurons, which ultimately project to biceps brachii during the elbow flexion portion of arm cycling, and increased spinal motoneuron excitability at the onset of elbow flexion during arm cycling. We conclude that supraspinal and spinal motoneuron excitability are phase- and task-dependent.

Prepubescent males are less susceptible to neuromuscular fatigue following resistance exercise.

PURPOSE: To determine if prepubescent and adult males have similar fatigue profiles following high and lower intensity knee extensions. METHODS: Ten male children and ten adults completed two sessions of three sets of high repetition (17 typical muscle endurance training) high repetition (High RM) or low repetition (seven typical strength training) maximum (Low RM) dynamic knee extensions. Voluntary and evoked contractile properties, heart rate (HR), and rating of perceived exertion (RPE) were assessed before and after each knee extension RM. RESULTS: Knee extension RM measures revealed that boys performed more (children set 2, 6.7 ± 0.5; set 3, 5.7 ± 0.5 vs. adult set 2, 5.2 ± 0.4; set 3, 3.5 ± 0.5; P < 0.001) repetitions, had a faster (children 39.9 ± 8.6 vs. adult 9.4 ± 3.7 bpm; P < 0.001) HR recovery and lower (6.4 ± 0.43; P < 0.001) RPE compared to adults (8.0 ± 0.4). Post-knee extension measures also revealed a smaller MVC force decrement (P < 0.001) with boys (94.3 % ± 6.1 vs. 76.3 % ± 4.1). Unlike adults, there were no significant decrements to children's evoked contractile properties or EMG. The greater boys' antagonist activation (children 125.7 % ± 9.2 vs. adult: 103.5 % ± 6.7; P < 0.001) post-knee extension would suggest muscle coordination changes as a primary mechanism for MVC force decrements. The lower RPE and similar agonist EMG activity may also indicate an inability of boys to perceive or produce a maximal effort. CONCLUSION: Independent of High or Low RM knee extensions, boys had greater neuromuscular fatigue resistance and recovered faster than adults.

Lower-limb and trunk muscle activation with back squats and weighted sled apparatus.

The back squat is a traditional resistance training exercise, whereas the resisted sled exercise is a relatively new resistance exercise. However, as there are no studies comparing muscle activation between the exercises, the objective of this study was to examine activity of leg and trunk muscles for both exercises. Ten healthy resistance-trained men participated in a randomized crossover design study consisting of 2 preparation sessions and 2 testing sessions. Electromyographic (EMG) activity of the rectus femoris, biceps femoris, gastrocnemius, lower erector spinae, and the transversus abdominis/internal obliques (TrA/IO) were monitored during a 20-step maximum push with the weighted sled apparatus and a 10 repetition maximum with a bilateral back squat. There were nonsignificant trends for the rectus femoris (p = 0.092: 8.6-16.7%) and biceps femoris (p = 0.09: 10.5-32.8%) to demonstrate higher activity with the sled and squat exercises, respectively. There were main effects for condition with 61.2% greater gastrocnemius EMG with the sled exercise (p = 0.01) and 74.5% greater erector spinae EMG activity with the squat (p = 0.002). There were no significant differences between the exercises for the TrA/IO. In summary, the sled and squat exercises provided similar EMG activity for the quadriceps, hamstrings, and TrA/IO. The squat provided higher lower erector spinae activation, whereas the sled had superior gastrocnemius activation. Depending on the movement-training specificity of the sport, either exercise may be used in a training program while acknowledging the differences in gastrocnemius and erector spinae activity.

The Effects of Load, Crank Position, and Sex on the Biomechanics and Performance during an Upper Body Wingate Anaerobic Test.

INTRODUCTION: The upper body Wingate Anaerobic Test (WAnT) is a 30-s maximal effort sprint against a set load (percentage of body mass). However, there is no consensus on the optimal load and no differential values for males and females, even when there are well-studied anatomical and physiological differences in muscle mass for the upper body. Our goal was to describe the effects of load, sex, and crank position on the kinetics, kinematics, and performance of the upper body WAnT. METHODS: Eighteen participants (9 females) performed three WAnTs at 3%, 4%, and 5% of body mass. Arm crank forces, 2D kinematics, and performance variables were recorded during each WAnT. RESULTS: Our results showed an increase of ~49% effective force, ~36% peak power, ~5° neck flexion, and ~30° shoulder flexion from 3% to 5% load ( P < 0.05). Mean power and anaerobic capacity decreased by 15%, with no changes in fatigue index ( P < 0.05). The positions of higher force efficiency were at 12 and 6 o'clock. The least force efficiency occurred at 3 o'clock ( P < 0.05). Sex differences showed that males produced 97% more effective force and 109% greater mean power than females, with 11.7% more force efficiency ( P < 0.001). Males had 16° more head/neck flexion than females, and females had greater elbow joint variability with 17° more wrist extension at higher loads. Males cycled ~32% faster at 3% versus 5% WAnT load with a 65% higher angular velocity than females. Grip strength, maximal voluntary isometric contraction, mass, and height positively correlated with peak and mean power ( P < 0.001). CONCLUSIONS: In conclusion, load, sex, and crank position have a significant impact on performance of the WAnT. These factors should be considered when developing and implementing an upper body WAnT.

A rapid rotation to an inverted seated posture inhibits muscle force, activation, heart rate and blood pressure.

Although previous studies have demonstrated neuromuscular and cardiovascular changes with slow inversion rates, emergencies, such as overturned vehicles and helicopters can occur rapidly. The purpose of this study was to investigate changes in neuromuscular and cardiovascular responses with rapid (1 s) and slower (3 s) transitions from upright to inverted seated positions. Twenty-two subjects performed separate and concurrent unilateral elbow flexion and leg extension maximal voluntary contractions (MVCs) for 6 s in an upright seated position and when inverted with 1 and 3 s rotations. Elbow flexion and leg extension force; biceps, triceps, quadriceps and hamstrings electromyographic (EMG) activity, heart rate (HR), systolic blood pressure (SBP) and diastolic blood pressure (DBP) were measured. Whether the elbow flexion or leg extension contractions occurred concurrently or individually, significant (p < 0.05) decreases in MVC force and EMG activity were found when inverted within 1 and 3 s rotations as compared to upright. Triceps and hamstrings EMG activity (p < 0.05) decreased when inverted within 1 s rotation as compared to upright. Following rotation, the maintenance of the inverted position (3-6 s timepoint) resulted in a significant (p < 0.05) increase in leg extension MVC as compared to the initial second of rotation to inversion. HR, SBP and DBP demonstrated (p < 0.001) decreases when inverted within 1 and 3 s rotations as compared to upright. In conclusion, this is the first study to show that irrespective of rotation speed, inversion inhibited neuromuscular and cardiovascular responses, similar to the more deliberate, slower rotation of previous inversion studies.

Exertional rhabdomyolysis in an acutely detrained athlete/exercise physiology professor.

The authors report a case of exercise-induced (exertional) rhabdomyolysis in a male athlete/exercise physiology professor who started a high-intensity resistance training program after a period of detraining. The subject performed 1 high-intensity resistance training session that consisted of 48 total sets of push-ups (24) and chin-ups (24) with no rest between the sets. Two days after the exercise session, the subject reported "Cola colored" urine. On arriving at the hospital, test results indicated elevated myoglobin and creatine kinase (CK) levels (59 159 U/L; normal is 20-200 U/L). Treatment included intravenous hydration with sodium bicarbonate to reduce myoglobin, blood work to monitor CK levels, and acupuncture from the shoulder to hand. Three weeks posttreatment, the subject started to exercise again. This case study illustrates that unaccustomed exercise in the form of high-intensity resistance training may be harmful (ie, severe delayed onset muscle soreness or even worse, as reported in this case, rhabdomyolysis) to detrained athletes.

An acute bout of self-myofascial release increases range of motion without a subsequent decrease in muscle activation or force.

Foam rolling is thought to improve muscular function, performance, overuse, and joint range of motion (ROM); however, there is no empirical evidence demonstrating this. Thus, the objective of the study was to determine the effect of self-myofascial release (SMR) via foam roller application on knee extensor force and activation and knee joint ROM. Eleven healthy male (height 178.9 ± 3.5 cm, mass 86.3 ± 7.4 kg, age 22.3 ± 3.8 years) subjects who were physically active participated. Subjects' quadriceps maximum voluntary contraction force, evoked force and activation, and knee joint ROM were measured before, 2 minutes, and 10 minutes after 2 conditions: (a) 2, 1-minute trials of SMR of the quadriceps via a foam roller and (b) no SMR (Control). A 2-way analysis of variance (condition × time) with repeated measures was performed on all dependent variables recorded in the precondition and postcondition tests. There were no significant differences between conditions for any of the neuromuscular dependent variables. However, after foam rolling, subjects' ROM significantly (p < 0.001) increased by 10° and 8° at 2 and 10 minutes, respectively. There was a significant (p < 0.01) negative correlation between subjects' force and ROM before foam rolling, which no longer existed after foam rolling. In conclusion, an acute bout of SMR of the quadriceps was an effective treatment to acutely enhance knee joint ROM without a concomitant deficit in muscle performance.

The Use of Elastic Resistance Bands to Reduce Dynamic Knee Valgus in Squat-Based Movements: A Narrative Review.

An elastic band wrapped around the distal thighs has recently been proposed as a method for reducing dynamic knee valgus (medial movement of the knee joint in the frontal/coronal plane) while performing squats. The rationale behind this technique is that, by using an external force to pull the knees into further knee valgus, the band both exaggerates the pre-existing movement and provides additional local proprioceptive input, cueing individuals to adjust their knee alignment. If these mechanisms are true, then elastic bands might indeed reduce dynamic knee valgus, which could be promising for use in injury prevention as excessive knee valgus may be associated with a greater risk of sustaining an ACL rupture and/or other knee injuries. Due to this possibility, certain athletic populations have already adopted the use of elastic bands for training and/or rehab, despite a limited number of studies showing beneficial findings. The purpose of this narrative review is to examine current literature that has assessed lower limb muscle activity and/or lower limb kinematics performance on squat-based movements with or without an elastic band(s). Importantly, this paper will also discuss the key limitations that exist in this area, propose suggestions for future research directions, and provide recommendations for training implementations. Level of Evidence: 5.