Muscular Response Research Articles

The influence of angiotensin I-converting enzyme (ACE) I/D gene polymorphism on cardiovascular and muscular adaptations following 8 weeks of isometric handgrip training (IHG) in untrained normotensive males.

We examined the association between the angiotensin I-converting enzyme (ACE) I/D gene polymorphism and isometric handgrip (IHG) training on cardiovascular and muscular responses among normotensive males. Thirty (II = 10, ID = 10, and DD = 10) normotensive untrained males underwent IHG training at 30% of their maximal voluntary contraction 3 days per week for 8 weeks. Cardiovascular and muscular variables were measured before IHG, after a session of IHG and after 8 weeks of IHG. No significant interaction effect was found between ACE I/D genotype and IHG training session on all dependent variables (all p > 0.05). There was a significant main effect of IHG training session on systolic blood pressure (SBP) (p = 0.002), mean arterial pressure (MAP) (p = 0.015) and handgrip strength (HGS) (p = 0.001) scores, while no difference in diastolic blood pressure (DBP), pulse pressure, or heart rate scores was found. A greater improvement in cardiovascular parameters following 8 weeks of IHG training was observed in participants with the D allele than the I allele (SBP reduction: ID+DD genotype group (-5.53 ± 6.2 mmHg) vs. II genotype group (-1.52 ± 5.3 mmHg)); MAP reduction: ID + DD genotype group (-2.80 ± 4.5 mmHg) vs. II genotype group (-1.45 ± 3.5 mmHg). Eight weeks of IHG training improved cardiovascular and muscular performances of normotensive men. Reduction in SBP and MAP scores in D allele carriers compared to I allele carriers indicates that the ACE I/D polymorphism may have an influence on IHG training adaptation in a normotensive population.

Task-Specificity of Muscular Responses During Motor Imagery: Peripheral Physiological Effects and the Legacy of Edmund Jacobson.

Motor imagery has become a key issue in cognitive neuroscience and particularly in fMRI research. However, peripheral physiological effects of motor imagery were already being studied a century ago with some research hypotheses even tracing back to Washburn (1916). This review focuses on research by Edmund Jacobson in the early 1930s. Jacobsen demonstrated that peripheral physiological effects rely on task-specific instructions: Bending the right arm elicits muscular responses in the right biceps, but not in the muscles of other limbs. This review discusses how Jacobsen examined this issue in a series of studies. This scientific spadework is worth recalling here because of its methodological innovations and its forward-looking discussion that even today, continues to be relevant for prospective research on this topic.

Differences in muscular and perceptual responses to a neck/shoulder fatiguing task between women and men

Fatigue is a risk factor for the development of work-related musculoskeletal disorders (WMSDs) of the neck/shoulder, and exertion is a state that connects the sensory/affective and physical aspects of fatigue. Relationships between ratings of perceived exertion (RPE) and electromyogram (EMG) signal characteristics have been identified. However, the sex-specific effects on these relationships are unclear and could be affected by personal factors such as skinfold thickness. 28 healthy young adults completed a fatiguing task with the arm held at shoulder height. Neck/shoulder EMG and RPE were collected at the end of each minute. Males showed stronger correlations between RPE with anterior deltoid (AD, rs = 0.37) and upper trapezius (UT, rs = 0.48) EMG, whereas females showed a weak relationship between RPE and UT EMG (rs = 0.22), and no relationship with AD EMG. Significant correlations were observed between biceps EMG and skinfold thickness in both males and females. Findings suggest that neck/shoulder perceived exertion is strongly associated to the activity of shoulder mobilizers (anterior deltoid) in men, whereas in women, it is rather associated to the activity of shoulder stabilizers (upper trapezius), and to a lesser extent. It is possible that in turn, these sex differences affect fatigue adaptation strategies. Skinfold thickness may be an important variable to consider when studying sex-specific characteristics of muscle fatigue.

Sarcolab pilot study into skeletal muscle\u2019s adaptation to long-term spaceflight

Spaceflight causes muscle wasting. The Sarcolab pilot study investigated two astronauts with regards to plantar flexor muscle size, architecture, and function, and to the underlying molecular adaptations in order to further the understanding of muscular responses to spaceflight and exercise countermeasures. Two crew members (A and B) spent 6 months in space. Crew member A trained less vigorously than B. Postflight, A showed substantial decrements in plantar flexor volume, muscle architecture, in strength and in fiber contractility, which was strongly mitigated in B. The difference between these crew members closely reflected FAK-Y397 abundance, a molecular marker of muscle’s loading history. Moreover, crew member A showed downregulation of contractile proteins and enzymes of anaerobic metabolism, as well as of systemic markers of energy and protein metabolism. However, both crew members exhibited decrements in muscular aerobic metabolism and phosphate high energy transfer. We conclude that countermeasures can be effective, particularly when resistive forces are of sufficient magnitude. However, to fully prevent space-related muscular deterioration, intersubject variability must be understood, and intensive exercise countermeasures programs seem mandatory. Finally, proteomic and metabolomic analyses suggest that exercise benefits in space may go beyond mere maintenance of muscle mass, but rather extend to the level of organismic metabolism.

Neural Control of Balance During Walking.

Neural control of standing balance has been extensively studied. However, most falls occur during walking rather than standing, and findings from standing balance research do not necessarily carry over to walking. This is primarily due to the constraints of the gait cycle: Body configuration changes dramatically over the gait cycle, necessitating different responses as this configuration changes. Notably, certain responses can only be initiated at specific points in the gait cycle, leading to onset times ranging from 350 to 600 ms, much longer than what is observed during standing (50–200 ms). Here, we investigated the neural control of upright balance during walking. Specifically, how the brain transforms sensory information related to upright balance into corrective motor responses. We used visual disturbances of 20 healthy young subjects walking in a virtual reality cave to induce the perception of a fall to the side and analyzed the muscular responses, changes in ground reaction forces and body kinematics. Our results showed changes in swing leg foot placement and stance leg ankle roll that accelerate the body in the direction opposite of the visually induced fall stimulus, consistent with previous results. Surprisingly, ankle musculature activity changed rapidly in response to the stimulus, suggesting the presence of a direct reflexive pathway from the visual system to the spinal cord, similar to the vestibulospinal pathway. We also observed systematic modulation of the ankle push-off, indicating the discovery of a previously unobserved balance mechanism. Such modulation has implications not only for balance but plays a role in modulation of step width and length as well as cadence. These results indicated a temporally-coordinated series of balance responses over the gait cycle that insures flexible control of upright balance during walking.

Young and older adults adapt automatic postural responses equivalently to repetitive perturbations but are unable to use predictive cueing to optimize recovery of balance stability

Processing of contextual cues has been proposed to modulate the generation of automatic postural responses to unanticipated balance perturbations. In this investigation, we compared young and older individuals in responses to sudden rotations of the support base inducing either planti- or dorsiflexion of the ankles. Assessment was made in conditions resulting from the combination of visual directional cueing of the forthcoming platform rotation, and block versus random sequences of platform rotation directions. Results showed that, for both rotation directions, the block sequence led to reduced magnitude of activation of distal agonist muscles and direction-specific modulation of ground reaction forces to recover body balance. Visual directional cueing, conversely, failed to modulate either muscular responses or forces applied to the support base through the feet for balance recovery. Effects were similar between ages, suggesting that aging does not increase the influence of cognition on the generation of automatic postural responses, and that adaptation to repeated postural perturbations over trials is preserved in healthy older individuals.

Muscular blood flow responses as an early predictor of the severity of diabetic neuropathy at a later stage in streptozotocin-induced type I diabetic rats: a diffuse correlation spectroscopy study.

We propose a novel application of diffuse correlation spectroscopy to evaluate microvascular malfunctions of muscle tissue affected by hyperglycemia and determine their correlation with the severity of diabetic neuropathy at a later stage. Microvascular responses of the thigh muscle and the mechanical pain threshold of the hind paw of streptozotocin-induced type I diabetic rats were continuously monitored once per week for 70 days. Significantly decreased baseline blood flow and reactive hyperemia responses were observed as early as 1 week after hyperglycemia induction. The reactive hyperemia response at 2 weeks of hyperglycemia was highly correlated with the mechanical pain threshold at 8 weeks, at which time a decreased pain threshold was statistically confirmed in hyperglycemic rats relative to controls.

The Effects of Whole Body Vibration Treatments on Lower Body Muscular Activity in Well-Trained Athletes from Different Sports Branches

A limited number of acute whole body vibration (WBV) studies have investigated the effects of WBV treatments which were applied with different vibration frequencies and amplitude combinations on lower extremity muscle activation of well-trained athletes from different sports branches. To compare the effects of WBV on lower extremity muscle activation via Surface Electromyography (sEMG) of well-trained athletes from different sports branches (soccer, basketball and swimming) during static and dynamic squat exercises. sEMG activities of Tibialis Anterior (TA), Gastrocnemius Medialis (GM), Vastus Medialis (VM), Rectus Femoris (RF), Vastus Lateralis (VL) and Biceps Femoris (BF) muscles of 7 male soccer players, 7 male basketball players, and 6 male swimmers were recorded during WBV applied in static squat and dynamic squat positions with different frequencies (30-35-40 Hz) and amplitude (2-4 mm) combinations separated from each other by 5 min passive rest periods. Each combination was applied for 30 sec. The highest muscle activation was determined in TA of the swimmers compared to soccer players during static squat with 4mm-30Hz WBV application (p=0.027). The lowest muscle activation was also determined in VL of the swimmers compared to soccer players during static squat with 2mm-40Hz WBV (p=0.049). During dynamic squat with 4mm-40Hz WBV, the highest muscle activity was determined in RF of the basketball players compared to swimmers (p=0.030). However, dynamic squat with 2mm-40Hz WBV application gave rise to the lowest muscle activation in VL of the basketball players compared to soccer players (p=0.042). Well-trained athletes from different sports branches demonstrated different neuromuscular responses to acute WBV treatments. WBV during dynamic squatting which was applied with 4mm-40 Hz may be more beneficial in enhancing neuromuscular performance acutely for well-trained male athletes since it resulted in higher levels of muscular activation responses according to the present study.

Consensus Statement on Perioperative Use of Neuromuscular Monitoring.

A panel of clinician scientists with expertise in neuromuscular blockade (NMB) monitoring was convened with a charge to prepare a consensus statement on indications for and proper use of such monitors. The aims of this article are to: (a) provide the rationale and scientific basis for the use of quantitative NMB monitoring; (b) offer a set of recommendations for quantitative NMB monitoring standards; (c) specify educational goals; and (d) propose training recommendations to ensure proper neuromuscular monitoring and management. The panel believes that whenever a neuromuscular blocker is administered, neuromuscular function must be monitored by observing the evoked muscular response to peripheral nerve stimulation. Ideally, this should be done at the hand muscles (not the facial muscles) with a quantitative (objective) monitor. Objective monitoring (documentation of train-of-four ratio ≥0.90) is the only method of assuring that satisfactory recovery of neuromuscular function has taken place. The panel also recommends that subjective evaluation of the responses to train-of-four stimulation (when using a peripheral nerve stimulator) or clinical tests of recovery from NMB (such as the 5-second head lift) should be abandoned in favor of objective monitoring. During an interim period for establishing these recommendations, if only a peripheral nerve stimulator is available, its use should be mandatory in any patient receiving a neuromuscular blocking drug. The panel acknowledges that publishing this statement per se will not result in its spontaneous acceptance, adherence to its recommendations, or change in routine practice. Implementation of objective monitoring will likely require professional societies and anesthesia department leadership to champion its use to change anesthesia practitioner behavior.

Trunk muscle strength and endurance assessed by two methods in the isokinetic dynamometer for able-bodied and post-stroke hemiparesis people

Trunk muscular function has been identified as an early predictor of health-related outcomes post-stroke, revealing unbalance on both sides changing muscular response in the axis of the body. Then, we aimed to compare the isokinetic measures of strength and endurance for trunk movement in antagonistic actions (flexion and extension), starting from the two different methods of assessment (seated compressed [SC] and semi-standing [SS]) for groups of able-bodied (control) and post-stroke hemiparesis (hemiparesis) people. A cross-sectional case-control study design was performed to compare strength (peak toque and normalized peak torque) and endurance (muscular power and total work) variables took at 60° and 120°/seconds, respectively, from the four observed conditions for a convenience sample composed by 26 volunteers (13 participants by group). The Functional Independence Measurement (FIM), the modified Ashworth Scale (mAS) and Mini Mental State Examination (MMSE) were the secondary variables to characterize the sample. Significant differences were detected by the two-way ANOVA followed by the Bonferroni post-test ( P < 0.05). For both groups and in all conditions, the extensor muscles performed around the doubled value recorded from all variables when compared to flexor muscles. Hemiparesis group revealed the expected weakness in comparison with control group, manifesting significant more strength and endurance when assessed by SS method, what was not observed in the control group. In conclusion, our results suggested that trunk extensor muscles are naturally stronger than flexor and post-stoke hemiparesis people are favored by SS method during isokinetic assessment.

Sub-threshold depolarizing pre-pulses can enhance the efficiency of biphasic stimuli in transcutaneous neuromuscular electrical stimulation

There is multiple evidence in the literature that a sub-threshold pre-pulse, delivered immediately prior to an electrical stimulation pulse, can alter the activation threshold of nerve fibers and motor unit recruitment characteristics. So far, previously published works combined monophasic stimuli with sub-threshold depolarizing pre-pulses (DPPs) with inconsistent findings—in some studies, the DPPs decreased the activation threshold, while in others it was increased. This work aimed to evaluate the effect of DPPs during biphasic transcutaneous electrical stimulation and to study the possible mechanism underlying those differences. Sub-threshold DPPs between 0.5 and 15 ms immediately followed by biphasic or monophasic pulses were administered to the tibial nerve; the electrophysiological muscular responses (motor-wave, M-wave) were monitored via electromyogram (EMG) recording from the soleus muscle. The data show that, under the specific studied conditions, DPPs tend to lower the threshold for nerve fiber activation rather than elevating it. DPPs with the same polarity as the leading phase of biphasic stimuli are more effective to increase the sensitivity. This work assesses for the first time the effect of DPPs on biphasic pulses, which are required to achieve charge-balanced stimulation, and it provides guidance on the effect of polarity and intensity to take full advantage of this feature.Graphical abstractIn this work, the effect of sub-threshold depolarizing pre-pulses (DPP) is investigated in a setup with transcutaneous electrical stimulation. We found that, within the tested 0–15 ms DPP duration range, the DPPs administered immediately before biphasic pulses proportionally increase the nerve excitability as visible in the M-waves recorded from the soleus muscle. Interestingly, these findings oppose published results, where DPPs, administered immediately before monophasic stimuli via implanted electrodes, led to decrease of nerve excitability.

Respiratory muscular response to obstructive maneuvers in non-invasively ventilated healthy subjects

The hypothesis of this study is that muscular activity measured through surface electromyography (sEMG) is useful to estimate the work of breathing (WOB) and respiratory mechanics. Thirty-two healthy volunteers were non-invasively ventilated, and an airflow resistor was attached to the airway circuit. sEMG signals from diaphragm, intercostal and sternocleidomastoid muscles were processed and compared with WOB changes.The airway resistance was increased from a median of 9.58 to 22.51 cmH2O/L/s adding a resistance of 20 cmH2O/L/s, achieving the lower compliance too. The respiratory mechanics changes implied linear increases in WOB, with Pearson correlation of 88.43% respect to changes in resistance. Muscles increased their activity in agreement with changes of WOB, being higher the increment in diaphragm followed by sternocleidomastoid.The non-invasively monitored respiratory muscles activity allowed evaluating the changes in WOB when it depends on addition of obstructive loads, confirming that it could be used to improve the available respiratory mechanics and WOB monitoring tools.

Active and Inactive Leg Hemodynamics during Sequential Single-Leg Interval Cycling.

Leg order during sequential single-leg cycling (i.e., exercising both legs independently within a single session) may affect local muscular responses potentially influencing adaptations. This study examined the cardiovascular and skeletal muscle hemodynamic responses during double-leg and sequential single-leg cycling. Ten young healthy adults (28 ± 6 yr) completed six 1-min double-leg intervals interspersed with 1 min of passive recovery and, on a separate occasion, 12 (six with one leg followed by six with the other leg) 1-min single-leg intervals interspersed with 1 min of passive recovery. Oxygen consumption, heart rate, blood pressure, muscle oxygenation, muscle blood volume, and power output were measured throughout each session. Oxygen consumption, heart rate, and power output were not different between sets of single-leg intervals, but the average of both sets was lower than the double-leg intervals. Mean arterial pressure was higher during double-leg compared with sequential single-leg intervals (115 ± 9 vs 104 ± 9 mm Hg, P < 0.05) and higher during the initial compared with second set of single-leg intervals (108 ± 10 vs 101 ± 10 mm Hg, P < 0.05). The increase in muscle blood volume from baseline was similar between the active single leg and the double leg (267 ± 150 vs 214 ± 169 μM·cm, P = 0.26). The pattern of change in muscle blood volume from the initial to second set of intervals was significantly different (P < 0.05) when the leg was active in the initial (-52.3% ± 111.6%) compared with second set (65.1% ± 152.9%). These data indicate that the order in which each leg performs sequential single-leg cycling influences the local hemodynamic responses, with the inactive muscle influencing the stimulus experienced by the contralateral leg.

Very Low Load resistance Exercise Is Augmented By Blood Flow Restriction In The Lower Body

Low load exercise to failure has been shown to elicit muscle hypertrophy similar to high load exercise. However, if the load is very low [i.e. 15% of one repetition maximum (1RM)], the contraction intensity may not disrupt blood flow enough to induce failure. Although unknown, the application of blood flow restriction (BFR) during very low load exercise may be necessary in order to reach failure. PURPOSE: To compare the acute responses associated with a hypertrophic stimulus during lower body exercise using a traditional high load (70% 1RM), very low load (15% 1RM) with no BFR, or in combination with moderate (40% arterial occlusion pressure (AOP)) or high (80% AOP) BFR pressure; coded as 70/0, 15/0, 15/40, and 15/80 respectively. METHODS: 22 participants completed 4 sets of unilateral knee extensions to failure (up to 90 repetitions) with each condition. Muscle thickness (MTh) and maximal voluntary contractions (MVC) were assessed before (Pre), immediately following (Post), and 15 minutes after exercise (15-Post). Electromyography (EMG) amplitude of the rectus femoris (RF) and vastus lateralis (VL) was assessed during the last 3 repetitions of each set. Data presented as mean (SD) with p≤0.05. RESULTS: There was an interaction for MTh, however, follow up tests revealed no differences within time points. Overall, MTh increased from Pre to Post [0.48 (0.17) cm], decreased at 15-post [-0.11 (0.18) cm], but remained elevated over Pre [0.36 (0.07) cm]. There was an interaction for MVC and follow up tests revealed differences at Post [15/80 < 15/0, 15/40, < 70/0] and 15-Post [15/0 < 15/80, 70/0]. All conditions decreased MVC at Post [-111.1 (48) Nm] and increased from Post to 15-Post [79.2 (43.1) Nm]. There was a main effect of condition for RF EMG, with 70/0 being greater than 15/80 [83 (37) vs. 57 (27) %MVC]. For VL EMG, there was a main effect of condition [70/0 > 15/80, 15/40, 15/0] and time [set 1< 2, 3, 4]. Typically, VL EMG was greater for 70/0 [106 (70) %MVC] compared to 15/0 [73 (21)], 15/40 [72 (30)], and 15/80 [64 (21)]. CONCLUSIONS: BFR with a higher pressure seemed to augment the acute muscular response to very low load exercise, making it closer to the response observed during high load exercise. This suggests that a higher BFR pressure may be necessary to induce hypertrophy when resistance training with very low loads.

A case study of optimal input-output system with sampled-data control: Ding et al. force and fatigue muscular control model

The objective of this article is to make the analysis of the muscular force response to optimize electrical pulses train using Ding et al. force-fatigue model. A geometric analysis of the dynamics is provided and very preliminary results are presented in the frame of optimal control using a simplified input-output model. In parallel, to take into account the physical constraints of the problem, partial state observation and input restrictions, an optimized pulses train is computed with a model predictive control, where a non-linear observer is used to estimate the state-variables.

Upper body kinematic and muscular variability in response to targeted rotator cuff fatigue

The rotator cuff muscles are prominent stabilizers of the shoulder and are vulnerable to muscle fatigue. Rotator cuff fatigue may result in subacromial impingement (SAI) through the superior translation of the humeral head. Scapular changes have been reported inconsistently, but may prevent SAI. The purpose of this study was to quantify changes in scapular kinematics, as well as muscle activity during glenohumeral motions following targeted rotator cuff fatigue. Ten healthy men completed four planar glenohumeral motions (cross-flexion, frontal, scapular, and sagittal plane elevation) prior to and immediately following a rotator cuff fatigue protocol on two separate days. Scapular kinematics and muscle activity of thirteen muscles were recorded. Scapular protraction decreased significantly with fatigue during scapular plane elevation (p < 0.001; ηp2 = 0.74). Although not significant, large effect sizes were found with decreased scapular protraction during elevation in the frontal (p = 0.012; ηp2 = 0.52) and sagittal planes (p = 0.007; ηp2 = 0.58), as well as decreased scapular medial rotation during cross-flexion (p = 0.008; ηp2 = 0.56). Between-subject variability (standard deviations from 2.3° to 14.5°) and within-subject day-to-day differences (upwards of 10° deviation in the opposite direction) were high among all kinematic changes following fatigue. Considerable day-to-day differences in scapular stabilizer muscle activity in response to fatigue were present. Due to the degrees of freedom at the upper extremity, individuals can employ a variety of compensatory strategies to fatigue. The variable compensatory strategies across the scapular stabilizers resulted in individual-specific scapular kinematic changes that could act as either impingement-sparing or impingement-promoting. The high variance in day-to-day differences within-subjects indicates that kinematic and muscular responses to fatigue may be adaptive within individuals over time.

Muscular and metabolic responses to different Nordic walking techniques, when style matters.

Due to poling action and upper body engagement, Nordic walking (NW) has additional health benefits with respect to conventional walking. The aim of this study was to evaluate the differences in muscle activation and metabolic responses between NW, performed with the technique suggested by NW instructors, and with some modifications in the way to move upper limb and poles. Ten NW instructors volunteered to walk on a treadmill at 5.5 km•h-1 in five conditions: walking (W), Nordic walking (NW), NW with a weak poling action (NWweak), with straight-upper limbs moving the shoulders (NWshoulder) and with elbow flexion-extension pattern and shoulder freezed (NWelbow). Poling forces, body segments and poles movement, upper and lower body muscle activation, as well as metabolic parameters were measured.All modified NW techniques elicited lower muscular activation and metabolic responses with respect to the suggested NW technique (P < 0.05). All NW techniques elicited higher muscular activation and metabolic responses than W. All parameters observed with the NWweak were lower than NW. A decreased activation of shoulder extensor muscles and increased activation of anterior deltoid muscle were the main features of NWshoulder. Lower triceps brachii muscle activation and reduced propulsive poling action with respect to NW were seen for NWelbow, resulting also in shorter steps.Nordic walking instructors, sport technicians and practitioners should be aware that any deviation from the technique usually suggested might lead to lower benefits. However it is worth to note that any walking technique with poles elicits higher metabolic responses and muscular activation than walking.

Muscular responses to testosterone replacement vary by administration route: a systematic review and meta-analysis.

BackgroundInconsistent fat‐free mass (FFM) and muscle strength responses have been reported in randomized clinical trials (RCTs) administering testosterone replacement therapy (TRT) to middle‐aged and older men. Our objective was to conduct a meta‐analysis to determine whether TRT improves FFM and muscle strength in middle‐aged and older men and whether the muscular responses vary by TRT administration route.MethodsSystematic literature searches of MEDLINE/PubMed and the Cochrane Library were conducted from inception through 31 March 2017 to identify double‐blind RCTs that compared intramuscular or transdermal TRT vs. placebo and that reported assessments of FFM or upper‐extremity or lower‐extremity strength. Studies were identified, and data were extracted and validated by three investigators, with disagreement resolved by consensus. Using a random effects model, individual effect sizes (ESs) were determined from 31 RCTs reporting FFM (sample size: n = 1213 TRT, n = 1168 placebo) and 17 reporting upper‐extremity or lower‐extremity strength (n = 2572 TRT, n = 2523 placebo). Heterogeneity was examined, and sensitivity analyses were performed.ResultsWhen administration routes were collectively assessed, TRT was associated with increases in FFM [ES = 1.20 ± 0.15 (95% CI: 0.91, 1.49)], total body strength [ES = 0.90 ± 0.12 (0.67, 1.14)], lower‐extremity strength [ES = 0.77 ± 0.16 (0.45, 1.08)], and upper‐extremity strength [ES = 1.13 ± 0.18 (0.78, 1.47)] (P < 0.001 for all). When administration routes were evaluated separately, the ES magnitudes were larger and the per cent changes were 3–5 times greater for intramuscular TRT than for transdermal formulations vs. respective placebos, for all outcomes evaluated. Specifically, intramuscular TRT was associated with a 5.7% increase in FFM [ES = 1.49 ± 0.18 (1.13, 1.84)] and 10–13% increases in total body strength [ES = 1.39 ± 0.12 (1.15, 1.63)], lower‐extremity strength [ES = 1.39 ± 0.17 (1.07, 1.72)], and upper‐extremity strength [ES = 1.37 ± 0.17 (1.03, 1.70)] (P < 0.001 for all). In comparison, transdermal TRT was associated with only a 1.7% increase in FFM [ES = 0.98 ± 0.21 (0.58, 1.39)] and only 2–5% increases in total body [ES = 0.55 ± 0.17 (0.22, 0.88)] and upper‐extremity strength [ES = 0.97 ± 0.24 (0.50, 1.45)] (P < 0.001). Interestingly, transdermal TRT produced no change in lower‐extremity strength vs. placebo [ES = 0.26 ± 0.23 (−0.19, 0.70), P = 0.26]. Subanalyses of RCTs limiting enrolment to men ≥60 years of age produced similar results.ConclusionsIntramuscular TRT is more effective than transdermal formulations at increasing LBM and improving muscle strength in middle‐aged and older men, particularly in the lower extremities.

ERECTOR SPINAE AND SCOLIOSIS IN A POPULATION WITH CEREBRAL PALSY: A PRELIMINARY STUDY

ABSTRACT Objective: To verify the relation of muscular response to the vestibular stimulation of the erector spinae, specifically longissimus thoracis and iliocostalis lumborum, with the origin of scoliosis in a population of individuals with level V cerebral palsy of the Gross Motor Function Classification System (GMFCS). Methods: Cross-sectional study of 12 individuals aged between four and 14 years. The muscular activity of the longissimus thoracis and iliocostalis lumborum was recorded by electromyography in the presence of anteroposterior and lateral imbalances, comparing it with that obtained in sitting position without imbalances. Scoliosis was assessed by radiological study following Cobb method. Results: Statistically significant differences were found between correct responses of both muscles to anteroposterior imbalances and absence of right thoracolumbar scoliosis (p=0.005; p=0.028), left thoracic scoliosis (p=0.005; p=0.046) and right lumbar scoliosis (p=0.005; p=0.046). Conclusions: The symmetry of muscular responses to anteroposterior imbalances, both of longissimus thoracis and iliocostalis lumborum, seems to be one of the factors that prevent the development of spine deviations in this population. Level of evidence: IV. Type of Study: Case series

Effects of load on the acute response of muscles proximal and distal to blood flow restriction.

To determine the effects of load and blood flow restriction (BFR) on muscular responses, we asked 12 participants to perform chest presses under four different conditions [30/0, 30/40, 50/0, and 50/40, presented as percentage one-repetition maximum (1RM)/percentage arterial occlusion pressure (AOP)]. Muscle thickness increased pre- to post-exercise [chest:mean 0.29, 95% confidence interval (CI) 0.21, 0.37 cm; triceps:mean 0.44, 95% CI 0.34, 0.54 cm], remaining elevated for 15min post-exercise. Electromyography amplitude was greater with 50% 1RM and increased over time for the first three repetitions of each set of chest presses. The last three repetitions differed across time only. AOP increased from pre- to post-exercise, augmented by BFR [30/0: mean 31, 95% CI 18, 44mmHg; 30/40: mean 39, 95% CI 28, 50mmHg; 50/0: mean 32, 95% CI 23, 41mmHg; 50/40: mean 46, 95% CI 32, 59mmHg). Tranquility decreased and physical exhaustion increased from the pre- to post-condition, with both parameters returning to the baseline 15min post-exercise level. In conclusion, load and BFR do not elicit meaningful differences in the acute response of chest press exercise taken to failure.