Brennan J. Thompson

Reliability of panoramic ultrasound imaging to simultaneously examine muscle size and quality of the medial gastrocnemius

Introduction: In this study we examined the test–retest reliability of panoramic brightness‐mode ultrasound (US) imaging to simultaneously measure both muscle size and quality from a single US image. Methods: Sixteen healthy, recreationally active men (age = 20.9 ± 2.5 years) volunteered for this investigation. Test–retest reliability was evaluated using intraclass correlation coefficients (ICCs) and the standard error of measurement as a percentage of the mean (SEM%). Muscle size [cross‐sectional area (CSA)], and muscle quality [echo intensity (EI)] of the medial gastrocnemius were examined on 2 separate days. Results: These measures demonstrated acceptable reliability between assessment days with ICCs and SEM% of 0.914 and 0.720 and 5.830 and 3.680 for CSA and EI, respectively. Conclusions: These results suggest that panoramic US imaging may be a reliable technique for simultaneous assessment of both muscle size and quality from a single US scan. Muscle Nerve 49: 736–740, 2014

Effect of instruction, surface stability, and load intensity on trunk muscle activity

The aim of this study was to assess the effect of verbal instruction, surface stability, and load intensity on trunk muscle activity levels during the free weight squat exercise. Twelve trained males performed a free weight squat under four conditions: (1) standing on stable ground lifting 50% of their 1-repetition maximum (RM), (2) standing on a BOSU balance trainer lifting 50% of their 1-RM, (3) standing on stable ground lifting 75% of their 1-RM, and (4) receiving verbal instructions to activate the trunk muscles followed by lifting 50% of their 1-RM. Surface EMG activity from muscles rectus abdominis (RA), external oblique (EO), transversus abdominis/internal oblique (TA/IO), and erector spinae (ES) were recorded for each condition and normalized for comparisons. Muscles RA, EO, and TA/IO displayed greater peak activity (39-167%) during squats with instructions compared to the other squat conditions (P=0.04-0.007). Peak EMG activity of muscle ES was greater for the 75% 1-RM condition than squats with instructions or lifting 50% of 1-RM (P=0.04-0.02). The results indicate that if the goal is to enhance EMG activity of the abdominal muscles during a multi-joint squat exercise then verbal instructions may be more effective than increasing load intensity or lifting on an unstable surface. However, in light of other research, conscious co-activation of the trunk muscles during the squat exercise may lead to spinal instability and hazardous compression forces in the lumbar spine.

Independent static balance training contributes to increased stability and functional capacity in community-dwelling elderly people: a randomized controlled trial

Objective: To evaluate the effectiveness of independently conducted static balance exercises within a fall-safe environment in elderly participants engaging in independent training. Design: Randomized two-group parallel controlled study. Setting: Retirement center, community dwelling. Subjects: Subjects, 25 male and female volunteers (aged 82.6 ± 6.1 years; weight 69.9 ± 97 kg; height 165 ± 6.9 cm; body mass index (BMI) 25.6 ± 2.6) residing in independent living facilities were randomly assigned to an experimental group or a control group. Intervention: The experimental group engaged in standing, static balancing, and mild leg exercise 12 minutes per session, three times per week for 12 weeks. Exercises were done independent of spotters within a rigid frame consisting of tethers connected to the subject so that he or she could not fall. The control group were given literature on prevention of falls. Main outcome measures: Functional ability and balance was assessed using the following tests: 30-second chair stand test, 8-foot up and go test, Berg Balance Scale, and a step-up test. Results: Comparison by repeated-measures ANOVA of the performance before and after the 12-week intervention yielded significant (P < 0.01) improvement for the experimental group over the control group in the 30-second chair test repetitions, in the 8-foot up and go test, in the balance assessment and in the leg function assessments. Conclusion: Standing, static balance exercises conducted independently without safety supervision led to improvements in balance, functional ability, and leg functioning in frail elderly people.

Barbell Deadlift Training Increases the Rate of Torque Development and Vertical Jump Performance in Novices

Abstract Thompson, BJ, Stock, MS, Shields, JE, Luera, MJ, Munayer, IK, Mota, JA, Carrillo, EC, and Olinghouse, KD. Barbell deadlift training increases the rate of torque development and vertical jump performance in novices. J Strength Cond Res 29(1): 1–10, 2015—The primary purpose of this study was to examine the effects of 10 weeks of barbell deadlift training on rapid torque characteristics of the knee extensors and flexors. A secondary aim was to analyze the relationships between training-induced changes in rapid torque and vertical jump performance. Fifty-four subjects (age, mean ± SD = 23 ± 3 years) were randomly assigned to a control (n = 20) or training group (n = 34). Subjects in the training group performed supervised deadlift training twice per week for 10 weeks. All subjects performed isometric strength testing of the knee extensors and flexors and vertical jumps before and after the intervention. Torque-time curves were used to calculate rate of torque development (RTD) values at peak and at 50 and 200 milliseconds from torque onset. Barbell deadlift training induced significant pre- to post-increases of 18.8–49.0% for all rapid torque variables (p < 0.01). Vertical jump height increased from 46.0 ± 11.3 to 49.4 ± 11.3 cm (7.4%; p < 0.01), and these changes were positively correlated with improvements in RTD for the knee flexors (r = 0.30–0.37, p < 0.01–0.03). These findings showed that a 10-week barbell deadlift training program was effective at enhancing rapid torque capacities in both the knee extensors and flexors. Changes in rapid torque were associated with improvements in vertical jump height, suggesting a transfer of adaptations from deadlift training to an explosive, performance-based task. Professionals may use these findings when attempting to design effective, time-efficient resistance training programs to improve explosive strength capacities in novices.

Acute effects of different volumes of dynamic stretching on vertical jump performance, flexibility and muscular endurance

The purpose of this study was to examine the acute effects of different volumes of a dynamic stretching routine on vertical jump (VJ) performance, flexibility and muscular endurance (ME). Twenty‐six males (age 22·2 ± 1·3 years) performed three separate randomized conditions: (i) a control (CON) condition (5‐min jog + 12 min of resting), (ii) a 5‐min jog + a dynamic stretching routine (DS1; 6·7 ± 1·3 min) and (iii) a 5‐min jog + a dynamic stretching routine with twice the volume (DS2; 12·1 ± 1·6 min). The dynamic stretching routine included 11 exercises targeting the hip and thigh musculature. VJ performance (jump height and velocity) and flexibility were measured prior to and following all conditions, while ME was measured following all conditions. The DS1 and DS2 conditions increased VJ height and velocity (P<0·01), while the CON condition did not change (P>0·05). When compared to the CON condition, the DS1 condition did not improve ME (P>0·05), whereas the DS2 condition resulted in a significant (15·6%) decrease in the number of repetitions completed (P<0·05). Flexibility increased following all conditions (P<0·01), while the DS1 condition was significantly greater (P<0·01) than the CON condition at post‐testing. These results suggest that dynamic stretching routines lasting approximately 6–12 min performed following a 5‐min jog resulted in similar increases in VJ performance and flexibility. However, longer durations of dynamic stretching routines may impair repetitive high‐intensity activities.

Reliability of Panoramic Ultrasound Imaging in Simultaneously Examining Muscle Size and Quality of the Hamstring Muscles in Young, Healthy Males and Females

The purpose of this study was to examine the reliability of ultrasound (US) measures of cross-sectional area (CSA), muscle thickness (MT) and echo intensity (EI) of the hamstrings, with comparisons between males and females. In 20 healthy participants (10 males, 10 females), CSA, MT and EI were measured from panoramic US scans of the hamstrings on 2 separate days. The intra-class correlation coefficients and standard errors of measurement as a percentage of the mean for CSA, MT and EI ranged from 0.715 to 0.984 and from 3.145 to 12.541% in the males and from 0.724 to 0.977 and from 4.571 to 17.890% in the females, respectively. The males had greater CSAs and MTs and lower EIs than the females (p = 0.002-0.049), and significant relationships were observed between CSA and MT (r = 0.714-0.938, p ≤ 0.001-0.023). From an overall reliability standpoint, these findings suggest that panoramic US may be a reliable technique for examining muscle size and quality of the hamstrings in both males and females.

Muscle group specific changes in the electromechanical delay following short-term resistance training

OBJECTIVES The time delay between the onset of a muscles electrical activity and force is believed to have important functional implications, and has been shown to decrease following resistance training in males. The purpose of this investigation was to examine changes in the voluntary electromechanical delay (EMD) for the leg extensors and flexors following a short-term resistance training intervention in females. DESIGN Pretest/posttest control group experiment. METHODS Twenty-two previously untrained females (mean±SD age=21±2 years; mass=65.4±13.3kg) were randomly assigned to training (n=10) and control (n=12) groups. The training group performed barbell back squats and deadlifts twice per week for four weeks. EMD for the vastus lateralis (extensors) and biceps femoris (flexors) was examined during maximal voluntary contractions at pre- and posttesting. Data were examined using analyses of covariance (ANCOVAs) with the pretest and posttest scores serving as the covariate and dependent variable, respectively, and by evaluating the number of participants that exceeded the minimal difference statistic. RESULTS For the leg extensors, the adjusted EMD posttest mean for the training group was significantly lower than that for the control group (74.3 vs. 91.8ms; p=0.015; ή(2)=0.275), and five training participants displayed decreases that exceeded the minimal difference. The ANCOVA for the leg flexors was not significant (adjusted means=98.0 vs. 90.0ms; p=0.487; ή(2)=.026). CONCLUSIONS Four weeks of multi-joint resistance training resulted in decreased EMD for the leg extensors, but not the flexors.

Effects of neuromuscular fatigue on electromechanical delay of the leg extensors and flexors in young men and women

Introduction: We examined the effects of neuromuscular fatigue on volitional electromechanical delay (EMD) of leg extensors and flexors between genders. Methods: Twenty‐one men and 20 women performed 2 maximal voluntary contractions (MVCs), followed by intermittent isometric contractions of leg extensors and flexors using a 0.6 duty cycle (6‐s contraction, 4‐s relaxation) at 50% of MVC until volitional fatigue was achieved. MVCs were again performed at 0, 7, 15, and 30 min post‐fatigue. Results: EMD was greater compared with baseline at all post‐fatigue time phases for the leg flexors (P = 0.001–0.007), while EMD was greater at Post0, Post15 and Post30 (P = 0.001–0.023) for the leg extensors. EMD was also greater for leg extensors compared with leg flexors only at Post0. Conclusion: No differential gender‐related fatigue effects on EMD were shown. There were different fatigue‐induced responses between leg extensors and flexors, with leg extensors exhibiting higher EMD immediately post‐fatigue. Muscle Nerve 52: 844–851, 2015

The influence of athletic status on maximal and rapid isometric torque characteristics and postural balance performance in Division I female soccer athletes and non-athlete controls.

The purpose of this study was to examine the effectiveness of maximal and rapid isometric torque characteristics of the hip extensor muscles and postural balance performance to discriminate between female collegiate soccer athletes and non‐athlete controls. Ten athletes (mean ± SE: age = 19·20 ± 0·36 year; mass = 62·23 ± 3·12 kg; height = 162·43 ± 1·70 cm) and 10 non‐athletes (age = 20·30 ± 0·40 year; mass = 69·64 ± 3·20 kg; height = 163·22 ± 2·10 cm) performed two isometric maximal voluntary contractions (MVCs) of the hip extensor muscles. Peak torque (PT) and absolute and relative rate of torque development (RTD) at early (0–50 ms) and late (100–200 ms) phases of muscle contraction were examined during each MVC. Postural balance was assessed using a commercially designed balance testing device, which provides a measurement of static stability based on sway index (SI). Results indicated that absolute and relative RTD at 0–50 ms (RTD50 and RTD50norm) were greater (P = 0·007 and 0·026), and postural SI was lower (P = 0·022) in the athletes compared with the non‐athletes. However, no differences (P = 0·375–0·709) were observed for PT nor absolute and relative RTD at 100–200 ms (RTD100–200 and RTD100–200norm). Significant relationships were also observed between RTD50 and RTD50norm and SI (r = −0·559 and −0·521; P = 0·010 and 0·019). These findings suggest that early rapid torque characteristics of the hip extensor muscles and postural balance performance may be sensitive and effective measures for discriminating between college‐aged athletes and non‐athletes. Coaches and practitioners may use these findings as performance evaluation tools to help in identifying athletes with both superior early rapid torque and balance performance abilities, which may possibly be an indicator of overall athletic potential.

Test-retest reliability and the minimal detectable change for achilles tendon length: a panoramic ultrasound assessment.

The purpose of the present study was to examine test-retest reliability and minimal detectable change (MDC) values for Achilles tendon (AT) length determined using panoramic ultrasound (US) imaging. Seventeen men (age = 21.0 ± 2.3 y) visited the laboratory on two separate days, where AT length was examined along the mid-longitudinal axis of the right lower leg with a portable B-mode panoramic US device. These measures were found to have acceptable reliability with intra-class correlation coefficient (ICC) and standard error of measurement (SEM) values of 0.954 and 4.43 mm (SEM% of the mean = 2.37%), respectively. In addition, the MDC for the panoramic US assessment of AT length was 12.27 mm (MDC% of the mean = 6.57%). These findings suggest that panoramic US imaging is a reliable technique for detection of clinically relevant changes in AT length and may therefore be a practical and time-efficient clinical tool for future studies examining AT length in vivo.