Eric J. Sobolewski

Age related differences in maximal and rapid torque characteristics of the leg extensors and flexors in young, middle-aged and old men

The decline in maximal and rapid isometric torque characteristics may compromise functional living abilities in aging adults while loco-motor muscle groups, such as the leg extensors and flexors, may exhibit different torque-time age related decreases. The purpose of the present study was to examine the age-related differences in maximal and rapid torque characteristics of the leg extensor and flexor muscle groups in young, middle-aged, and old men. Sixty-five healthy men were categorized by age as young (n=25; mean±SD age=24.9±3.0 years), middle-aged (n=22; age=50.6±4.0 years), and old (n=18; age=66.8±4.5 years). Participants performed maximal voluntary contractions (MVCs) of the leg extensors and flexors and an estimated thigh cross sectional area (eThighCSA) assessment. Peak torque (PT), peak rate of torque development (RTDpeak), absolute RTD and the contractile impulse (IMPULSE) were calculated at time intervals of 30, 50, 100 and 200 ms from the torque-time curve. Relative RTD was calculated at 10, 20, 30, 40 and 50% of MVC from the normalized torque-time curves. PT, RTDpeak and later rapid torque variables (RTD100, RTD200, and IMPULSE200) were greater (P≤0.05) in the young and middle-aged when compared to the old men for both muscle groups. Early (RTD30,50; IMPULSE30,50) and late (IMPULSE100) rapid torque variables were greater (P≤0.05) for the young and middle-aged than the old men for the leg extensors but not the leg flexors, except for RTD30, in which there was no difference between young and old. There were no differences for all relative RTD variables between age groups (P>0.05). eThighCSA was lower in the old compared to the young (P=0.001) and middle-aged (P=0.016) men. Maximal and rapid torque characteristics were preserved in middle-aged men but greatly reduced in older men with differential effects at early and late portions of the torque-time curve between the leg extensors and flexors. Significant decreases in absolute maximal and rapid torque production with no change in relative RTD across age groups and lower eThighCSA in old men may suggest that the loss of rapid torque producing capacities observed in older men may be largely a function of mechanisms associated with loss of muscle strength and muscle mass.

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

Can maximal and rapid isometric torque characteristics predict playing level in division I American collegiate football players

Abstract Thompson, BJ, Ryan, ED, Sobolewski, EJ, Smith, DB, Conchola, EC, Akehi, K, and Buckminster, T. Can maximal and rapid isometric torque characteristics predict playing level in division I American collegiate football players? J Strength Cond Res 27(3): 655–661, 2013—The purpose of this study was to determine if maximal and rapid isometric torque characteristics could discriminate starters from nonstarters in elite Division I American collegiate football players. Sixteen starters (mean ± SD: age = 20.81 ± 1.28 years; height = 184.53 ± 6.58 cm; and mass = 108.69 ± 22.16 kg) and 15 nonstarters (20.40 ± 1.68 years; 182.27 ± 10.52 cm; and 104.60 ± 22.44 kg) performed isometric maximal voluntary contractions (MVCs) of the leg flexor and extensor muscle groups. Peak torque (PT), rate of torque development (RTD), the time to peak RTD (TTRTDpeak), contractile impulse (IMPULSE), and absolute torque values (TORQUE) at specific time intervals were calculated from a torque-time curve. The results indicated significant and nonsignificant differences between starters and nonstarters for the early rapid leg flexion torque characteristics that included RTD, IMPULSE, and TORQUE at 30 and 50 milliseconds, and TTRTDpeak. These variables also demonstrated the largest effect sizes of all the variables examined (0.71–0.82). None of the leg extensor variables, leg flexion PT, or later leg flexion rapid torque variables (≥100 milliseconds) were significant discriminators of playing level. These findings suggest that the early rapid leg flexion torque variables may provide an effective and sensitive muscle performance measurement in the identification of collegiate football talent. Further, coaches and practitioners may use these findings when designing training programs for collegiate football players with the intent to maximize rapid leg flexion characteristics.

Consistency of rapid muscle force characteristics: influence of muscle contraction onset detection methodology.

The purpose of this study was to investigate the consistency of commonly reported rapid force characteristics utilizing both automated and manual muscle contraction onset detection methods. Twenty-four healthy volunteers performed isometric strength testing of the plantar flexor muscle group on two nonconsecutive days. Test-retest reliability was evaluated using intraclass correlation coefficients (ICCs), standard errors of measurement (SEM), and the SEM as a percentage of the mean (SEM%) for rate of force development (RFD), relative RFD, contractile impulse, and absolute force-time values at various epoch durations using automated and manual onset detection methods. For all rapid force variables, ICC and SEM% values ranged from 0.52 to 0.96 and 7.56% to 37.56%, respectively. For the majority of these variables (20 of 23), the automated onset detection method resulted in higher ICC and lower SEM% values compared to the manual onset detection method. Regardless of onset detection methodology, the consistency of relative RFD values declined following 50% of MVC. Collectively, these findings indicated that commonly evaluated rapid muscle force variables demonstrated acceptable relative and absolute consistency values. However, these values were generally superior for the automated onset detection methodology. Additionally, the consistency of relative RFD values declines following 50% MVC and therefore should be evaluated with caution.

Functional hamstrings: quadriceps ratios in elite women's soccer players

Abstract We compared starters and non-starters for various isokinetic strength variables in elite women’s soccer players. A convenience sample of 10 starters (mean ± s; age = 20 ± 2 years; height = 170 ± 4 cm; body mass = 65 ± 5 kg) and 7 non-starters (age = 20 ± 1 years; height = 164 ± 3 cm; body mass = 63 ± 4 kg) performed maximal voluntary muscle actions of the leg extensors (concentric) and flexors (eccentric) on an isokinetic dynamometer in order to measure concentric peak torque for the leg extensors, eccentric peak torque for the leg flexors, and the functional hamstrings:quadriceps (H:Q) ratio at 1.047 rad · s-1 and 4.189 rad · s-1 concentric peak torque for the leg extensors was not different between starters and non-starters. However, it was greater at 1.047 rad · s-1 than at 4.189 rad · s-1 in both groups. Eccentric peak torque for the leg flexors was greater for the starters versus non-starters at 4.189 rad · s-1. Eccentric strength of the leg flexors at fast movement velocities may be used as an effective physiological profile and may discriminate between playing status in elite women’s soccer players.

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.

Relationships between rapid isometric torque characteristics and vertical jump performance in division i collegiate American football players: Influence of body mass normalization

Abstract Thompson, BJ, Ryan, ED, Sobolewski, EJ, Smith, DB, Akehi, K, Conchola, EC, and Buckminster, T. Relationships between rapid isometric torque characteristics and vertical jump performance in division I collegiate American football players: Influence of body mass normalization. J Strength Cond Res 27(10): 2737–2742, 2013—The purpose of the present study was to examine the relationships between absolute and body mass–normalized rapid isometric torque variables and vertical jump (VJ) performance of the leg extensors and flexors in elite National Collegiate Athletic Association Division I Football Bowl Subdivision collegiate American football players. Thirty-one players performed isometric maximal voluntary contractions of the leg extensor and flexor muscle groups and a countermovement VJ. Rate of torque development (RTD) and the contractile impulse (IMPULSE) were determined from 0 to 30, 0 to 50, 0 to 100, and 0 to 200 milliseconds from the onset of muscular contraction. The relationships between absolute and normalized rapid torque variables and VJ performance were assessed using correlation coefficients (r). There were no significant correlations (p > 0.05) observed between the absolute rapid torque variables and VJ performance, except for leg flexion RTD at 0–200 milliseconds (p = 0.024). All normalized rapid torque variables of the leg extensors and flexors were significantly correlated to VJ performance (p ⩽ 0.001–0.026). These findings indicated that normalizing rapid torque variables to body mass improves the relationships between isometric rapid torque variables and VJ performance and normalized leg extension and flexion are both similarly related to VJ performance. Strength and conditioning professionals may use these findings in an attempt to identify and monitor dynamic sport performance. Furthermore, future studies examining the relationship between dynamic on the field performances and laboratory-based isometric strength testing may consider including normalized rapid torque variables.

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.

Influence of maximum range of motion and stiffness on the viscoelastic stretch response

We examined the influence of maximum range of motion (MROM) and passive stiffness on the viscoelastic stretch response.

Neural and muscular contributions to the age-related reductions in rapid strength

Introduction The purposes of this study were to investigate the age-related differences in absolute and normalized plantarflexion rate of torque development (RTD) at early (0–50 ms) and late (100–200 ms) time intervals and to examine specific neural and muscular mechanisms contributing to these differences. Methods Thirty-two young (20.0 ± 2.1 yr) and 20 older (69.5 ± 3.3 yr) recreationally active men performed rapid plantarflexion isometric muscle actions to examine absolute and normalized RTD and muscle activation using EMG at early and late time intervals. Ultrasonography was used to examine medial gastrocnemius muscle size, echo intensity (EI), and muscle architecture (fascicle length [FL] and pennation angle [PA]). Results The older men were weaker (23.9%, P < 0.001) and had lower later absolute and normalized RTD (P = 0.001–0.034) variables when compared with the young men. The older men also had higher EI (P < 0.001), smaller PA (P = 0.004), and lower later EMG amplitude values (P = 0.009–0.046). However, there were no differences in early RTD and EMG amplitude values, muscle size, or FL between groups (P = 0.097–0.914). Lower late RTD values were related to higher EI, smaller PA, and lower EMG amplitude values (r = −0.28–0.59, P = 0.001–0.044); however, late RTD values were no longer related to PA after normalizing to peak torque. Conclusions Age-related alterations in muscle quality (EI), architecture, and muscle activation may influence rapid torque production at late time intervals (≥100 ms) from contraction onset. These findings highlight specific neuromuscular factors that influence the age-related reductions in RTD, which has been shown to significantly influence function and performance in older adults.