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The purpose of this study was to investigate the effects of sex, muscle thickness, and subcutaneous fat thickness (SFT) on corticospinal excitability outcome measures of the biceps brachii. Eighteen participants (10 males and 8 females) completed this study. Ultrasound was used to assess biceps brachii muscle thickness and the overlying SFT. Transcranial magnetic stimulation (TMS) was used to determine corticospinal excitability by inducing motor‐evoked potentials (MEPs) at eight different TMS intensities from 90% to 160% of active motor threshold (AMT) from the biceps brachii during an isometric contraction of the elbow flexors at 10% of maximum voluntary contraction (MVC). Biceps brachii maximal compound muscle action potential (Mmax) was also recorded prior to and after TMS. Males had higher (p < 0.001) biceps brachii muscle thickness and lower SFT, produced higher levels of MVC force and had, on average, higher (p < 0.001) MEP amplitudes at lower (p < 0.05) percentages of maximal stimulator output than females during the 10% elbow flexion MVC. Multiple linear regression modeling revealed that sex was not associated with any of the neurophysiological parameters examined, while SFT showed a positive association with the stimulation intensity required at AMT (p = 0.035) and a negative association with biceps brachii pre‐stimulus electromyography (EMG) activity (p = 0.021). Additionally, there was a small positive association between muscle thickness and biceps brachii pre‐stimulus EMG activity (p = 0.049). Overall, this study suggests that some measures of corticospinal excitability may be different between the sexes and influenced by SFT and muscle thickness. [ABSTRACT FROM AUTHOR]

The association of localized pain sensitivity in the residual limb and prosthesis use has clinical implications, however, rarely been assessed. This study aimed to investigate pain sensitivity and explore its range, variability, and association with prosthesis use alongside other demographic and clinical characteristics of veterans with transtibial amputation. Pain sensitivity was determined as pressure pain threshold (PPT) and pressure tolerance (PT) in 19 male veterans with a mean age of 49.5 years using pressure algometry at 12 anatomical locations on the residual limb. A comparison of pain sensitivity at each location, and among anatomical locations and participants was explored using independent t-test, analysis of variance, and Kruskal--Wallis tests, respectively. Pain sensitivity range (PSR), the difference between PT and PPT, was significantly different (p < 0.05) at mid-patellar tendon, medial tibial flare, and the distal end of the tibia. The lowest PPT and PT (20.5 and 33 Ncm-2, p = 0.13) were recorded at the distal end of the residual limb, and the highest PPT and PT (73.4 and 94.3 Ncm-2, p = 0.03) were recorded at the mid-patellar tendon. Pain sensitivity was significantly different among anatomical locations and participants. The correlation tests (Pearson and partial eta squared) showed non-significant associations of pain sensitivity with participants' demographic and clinical characteristics except for daily prosthesis use. The mid-patellar tendon, medial tibial flare, and distal end of the tibia revealed the lowest pain hypersensitivity due to higher PSR. Longer daily prosthesis use was associated with increased pain sensitivity. [ABSTRACT FROM AUTHOR]

The aim of this study was to compare the muscle activity of the gluteus medius (GMe), gluteus maximus (GMa), biceps femoris (BF), vastus lateralis (VL), vastus medialis (VM) and erector spinae (ES) as well as medial knee displacement (MKD) while using varying stiffness resistance bands (red: 1.68 kg; black: 3.31 kg; gold: 6.44 kg) during a barbell back squat (BBS) among males and females. A total of 23 (females: 11) resistance trained people were recruited for this study. Muscle activity was measured using electromyography, and motion capture cameras tracked lower-limb kinematics and MKD. Three resistance bands were placed at the distal end of the femur while performing a BBS at their 85% repetition maximum (RM). Parametric and non-parametric statistical analyses were conducted with the alpha level of 0.05. The gold resistance band resulted in a smaller knee-width-index value (i.e., greater MKD) compared to other bands (p < 0.01). Males exhibited less MKD compared to females during the BBS for each resistance band (p = 0.04). Males produced greater VL activity when using the black and gold resistance bands during the BBS (p = 0.03). When using a gold resistance band, the GMe muscle activation was higher compared to other resistance bands (p < 0.01). VM muscle activity was reduced when using a gold resistance band compared to no band condition (p < 0.01). BF (p = 0.39) and ES (p = 0.88) muscle activity did not change when using different resistance bands. As a result, females may be at a biomechanical disadvantage when using resistance bands compared to males while performing the BBS hindering them from optimal performance. [ABSTRACT FROM AUTHOR]

The objective of this study was to determine the relationship between specific performance measures and hockey skating speed. Thirty competitive secondary school and junior hockey players were timed for skating speed. Off-ice measures included a 40-yd (36.9-m) sprint, concentric squat jump, drop jump, 1 repetition maximum leg press, flexibility, and balance ratio (wobble board test). Pearson product moment correlations were used to quantify the relationships between the variables. Electromyographic (EMG) activity of the dominant vastus lateralis and biceps femoris was monitored in 12 of the players while skating, stopping, turning, and performing a change-of-direction drill. Significant correlations (p < 0.005) were found between skating performance and the sprint and balance tests. Further analysis demonstrated significant correlations between balance and players under the age of 19 years (r = -0.65) but not those over 19 years old (r = -0.28). The significant correlations with balance suggested that stability may be associated with skating speed in younger players. The low correlations with drop jumps suggested that short contact time stretch-shortening activities (i.e., low amplitude plyometrics) may not be an important factor. Electromyographic activities illustrated the very high activation levels associated with maximum skating speed. KEY WORDS. electromyography, balance, speed, flexibility, strength

The objective of this study was to investigate whether a warm-up consisting of a series of maximal contractions would augment the force and activation of subsequent leg extensor contractions. Both voluntary and evoked isometric contractions were tested to determine the mechanisms underlying the response. Nine subjects were tested for twitch, tetanic, submaximal (30%), and maximal voluntary contractile (MVC) properties before and after (1, 5, 10, and 15 minutes) one to three 10-second MVCs. MVC force either did not change following 1-2 MVCs or was depressed at 10 and 15 minutes after 3 MVCs. MVC activation was decreased (4.4-6.9%) throughout recovery, whereas submaximal contractions were minimally affected. Although overall, twitches were potentiated (15.5-19.8%) posttest, 3 MVCs had significantly greater twitch potentiation than 1 or 2 MVCs at 5 and 10 minutes. Results suggest that voluntary and evoked contractions respond differently to prior 10-second MVCs. In the present study, a warm-up routine of 1-3 MVCs of a 10-second duration did not enhance subsequent voluntary performance. KEY WORDS. quadriceps, interpolated twitch technique, electromyography, rate of force development, twitch, tetanus, maximum voluntary contractions

This study examined the influence of the TherabandTM CLX gold band on lower-limb muscle activity and kinematics during an overhead barbell squat. Participants performed two sets (band and no-band) of 12 repetitions of overhead barbell squats at 25% bodyweight. Three-dimensional kinematics were measured using motion capture with rigid bodies placed bilaterally on the foot, shank, thigh and thorax. Electromyography was collected from seven, bilateral muscles of the lower-limb and was unchanged for all muscles between conditions. Medial knee collapse was calculated using a knee-width index (KWI) ratio of the distance between the lateral epicondyles of the femur and the lateral malleoli. Average KWI was smaller during the band condition for the concentric (No band: 0.99 ± 0.05, Band: 0.97 ± 0.06, p < 0.05) and eccentric phases (No band: 1.00 ± 0.06, Band: 0.97 ± 0.05, p < 0.05). KWI was significantly smaller with the use of the TherabandTM CLX. As the gold band is the strongest of the CLX offerings, any benefit of increased proprioception may have been lost due to the high resistance of the band. Further research examining the dose-response of elastic band resistance to knee alignment may be needed to inform proper exercise prescription. [ABSTRACT FROM AUTHOR]