The purpose of this study was to examine the relationship between muscle architecture of the triceps brachii (TB) and joint performance during concentric elbow extensions. Twenty-two men performed maximal isometric and concentric elbow extensions against various loads. Joint torque and angular velocity during concentric contractions were measured, and joint power was calculated. Muscle length, cross-sectional areas, and volume of TB were measured from magnetic resonance images. Pennation angle (PA) of TB at rest was determined by ultrasonography. The PA was significantly correlated with the maximal isometric torque (r = .471), but not to the torque normalized by muscle volume (r = .312). A significant correlation was found between PA and the angular velocity at 0 kg load (r = .563), even when the angular velocity was normalized by the muscle length (r = .536). The PA was significantly correlated with the maximal joint power (r = .519), but not with the power normalized by muscle volume (r = .393). These results suggest that PA has a positive influence on the muscle shortening velocity during an unloaded movement, but does not have a significant influence on the maximum power generation in untrained men.
Taku Wakahara, Hiroaki Kanehisa, Yasuo Kawakami, Tetsuo Fukunaga and Toshimasa Yanai
Christopher Kuenze, Jay Hertel, Susan Saliba, David R. Diduch, Arthur Weltman and Joseph M. Hart
Normal, symmetrical quadriceps strength is a common clinical goal after anterior cruciate ligament reconstruction (ACLR). Currently, the clinical thresholds for acceptable unilateral quadriceps function and symmetry associated with positive outcomes after return to activity are unclear.
To establish quadriceps-activation and knee-extension-torque cutoffs for clinical assessment after return to activity after ACLR.
Descriptive laboratory study.
22 (10 female, 12 male; age = 22.5 ± 5.0 y, height = 172.9 ± 7.1 cm, mass = 74.1 ± 15.5 kg, months since surgery = 31.5 ± 23.5) recreationally active persons with a history of unilateral, primary ACLR at least 6 months prior and 24 (12 female/12 male, age = 21.7 ± 3.6 y, height = 168.0 ± 8.8 cm, mass = 69.3 ± 13.6 kg) recreationally active healthy participants.
Main Outcome Measures:
Patient-reported measures of pain, knee-related function, and physical activity level were recorded for all participants. Normalized knee-extension maximum-voluntary-isometric-contraction (MVIC) torque (Nm/kg) and quadriceps central-activation ratio (CAR, %) were measured bilaterally in all participants. Receiver-operator-characteristic (ROC) curves were used to establish thresholds for unilateral measures of normalized knee-extension MVIC torque and quadriceps CAR, as well as limb-symmetry indices (LSI). ROC curves then established clinical thresholds for normalized knee-extension MVIC torque and quadriceps CAR LSIs associated with healthy knee-related function.
Involved-quadriceps CAR above 89.3% was the strongest unilateral indicator of healthy-group membership, while quadriceps CAR LSI above 0.996 and knee-extension MVIC torque above 0.940 were the strongest overall indicators. Unilateral normalized knee-extension MVIC torque above 3.00 Nm/kg and quadriceps CAR LSI above 0.992 were the best indicators of good patient-reported knee-related outcomes.
Threshold values established in this study may provide a guide for clinicians when making return-to-activity decisions after ACLR. Normalized knee-extension MVIC torque (>3.00 Nm/kg) and quadriceps CAR symmetry (>99.6%) are both strong indicators of good patient-reported outcomes after ACLR.
Cindy Y. Lin, Liang-Ching Tsai, Joel Press, Yupeng Ren, Sun G. Chung and Li-Qun Zhang
Gluteal-muscle strength has been identified as an important component of injury prevention and rehabilitation in several common knee injuries. However, many conventionally prescribed gluteal-strengthening exercises are not performed during dynamic weight-bearing activities, which is when most injuries occur.
To compare lower-limb muscle-activation patterns between conventional gluteal-strengthening exercises and off-axis elliptical exercises with motorized foot-plate perturbations designed to activate gluteal muscles during dynamic exercise.
Twelve healthy volunteers (26.1 ± 4.7 y) participated in the study. They performed 3 conventional exercises (single-leg squat, forward lunge, and clamshell) and 3 elliptical exercises (regular, while resisting an adduction force, and while resisting an internal-rotation torque). Gluteus medius (GMed) and maximus (GMax), quadriceps, hamstrings, and gastrocnemius muscle activations during each exercise were recorded using surface electromyography (EMG) and normalized to maximal voluntary isometric contraction (MVIC).
Normalized GMed EMG was the highest during the adduction-resistance elliptical exercise (22.4% ± 14.8% MVIC), significantly greater than forward lunge (8.2% ± 3.8% MVIC) and regular elliptical (6.4% ± 2.5% MVIC) and similar to clamshell (19.1% ± 8.8% MVIC) and single-leg squat (18.4% ± 7.9% MVIC). Normalized GMax EMG during adduction-resistance (11.1% ± 7.6% MVIC) and internal-rotation-resistance elliptical (7.4% ± 3.8% MVIC) was significantly greater than regular elliptical (4.4% ± 2.4% MVIC) and was similar to conventional exercises. The single-leg squat required more muscle activation from the quadriceps and gastrocnemius than the elliptical exercises.
Off-axis elliptical exercise while resisting an adduction force or internal-rotation torque activates gluteal muscles dynamically while avoiding excessive quadriceps activation during a functional weight-bearing activity compared with conventional gluteal-strengthening exercises.
Min-Hyeok Kang, Dong-Kyu Lee, Kyung-Hee Park and Jae-Seop Oh
Ankle-dorsiflexion range of motion has often been measured in the weight-bearing condition in the clinical setting; however, little is known about the relationship between the weight-bearing-lunge test (WBLT) and both ankle kinematics and performance on dynamic postural-control tests.
To examine whether ankle kinematics and performance on the Lower Quarter Y-Balance Test (YBT-LQ) are correlated with results of the WBLT using an inclinometer and tape measure.
University motionanalysis laboratory.
30 physically active participants.
Main Outcome Measures:
The WBLT was evaluated using an inclinometer and a tape measure. The reach distances in the anterior, posteromedial, and posterolateral directions on the YBT-LQ were normalized by limb length. Ankle dorsiflexion during the YBT-LQ was recorded using a 3-dimensional motion-analysis system. Simple linear regression was used to examine the relationship between the WBLT results and both ankle dorsiflexion and the normalized reach distance in each direction on the YBT-LQ.
The WBLT results were significantly correlated with ankle dorsiflexion in all directions on the YBT-LQ (P < .05). A strong correlation was found between the inclinometer measurement of the WBLT and ankle dorsiflexion (r = .74, r 2 = .55), whereas the tape-measure results on the WBLT were moderately correlated with ankle dorsiflexion (r = .64, r 2 = .40) during the anterior reach on the YBT-LQ. Only the normalized anterior reach distance was significantly correlated with the results for the inclinometer (r = .68, r 2 = .46) and the tape measure (r = .64, r 2 = .41) on the WBLT.
Inclinometer measurements on the WBLT can be an appropriate tool for predicting the amount of ankle dorsiflexion during the YBT-LQ. Furthermore, WBLT should be measured in those who demonstrate poor dynamic balance.
Gianluca Vernillo, Alfredo Brighenti, Eloisa Limonta, Pietro Trabucchi, Davide Malatesta, Grégoire P. Millet and Federico Schena
To quantify changes in skeletal-muscle oxygenation and pulmonary O2 uptake (V̇O2) after an extreme ultratrail running bout.
Before (PRE) and after (POST) the race (330-km, 24000 D±), profiles of vastus lateralis muscle oxygenation (ie, oxyhemoglobin [O2Hb], deoxyhemoglobin [HHb], and tissue oxygenation index [TOI]) and V̇O2 were determined in 14 athletes (EXP) and 12 control adults (CON) during two 4-min constant-load cycling bouts at power outputs of 1 (p1) and 1.5 (p1.5) W/kg performed in randomized order.
At POST, normalized [HHb] values increased (p1, +38.0%; p1.5, +27.9%; P < .05), while normalized [O2Hb] (p1, –20.4%; p1.5, –14.4%; P < .05) and TOI (p1, –17.0%; p1.5, –17.7%; P < .05) decreased in EXP. V̇O2 values were similar (P > 0.05). An “overshoot“ in normalized [HHb]:V̇O2 was observed, although the increase was significant only during p1.5 (+58.7%, P = .003). No difference in the aforementioned variables was noted in CON (P > .05).
The concentric and, particularly, the eccentric loads characterizing this extreme ultratrail-running bout may have led to variations in muscle structure and function, increasing the local muscle deoxygenation profile and the imbalance between O2 delivery to working muscles and muscle O2 consumption. This highlights the importance of incorporating graded training, particularly downhill bouts, to reduce the negative influence of concentric and severe eccentric loads to the microcirculatory function and to enhance the ability of runners to sustain such loading.
Erik A. Wikstrom, Robert B. Anderson and Tricia Hubbard-Turner
Those with posttraumatic ankle osteoarthritis have a variety of sensorimotor impairments. However, no investigation has determined the effect of posttraumatic ankle osteoarthritis on stair climbing. The purpose of this study was to determine if stair ascent and descent kinetics are altered in those with posttraumatic ankle osteoarthritis. Those with posttraumatic ankle osteoarthritis had lower self-reported function than age-matched controls. Normalized peak vertical ground reaction forces during the weight acceptance phase of stair ascent and descent were also different between groups. The results suggest that those with ankle osteoarthritis have a reduced ability to control their body mass while stair climbing.
Gwen E. Chapman
This paper uses a Foucauldian framework for understanding how human experience is shaped by relations of power to explore the weight management practices of members of a women’s lightweight rowing team. Like other forms of disciplinary power, making weight involves implementing a regimen governed by normalizing assumptions, maintained through self-monitoring, and supported by discourse. The practices of making weight also are examined as a technology of the self that the rowers used to create and understand themselves. The position of women’s sport at the intersection of sports and gender discourse offered the rowers opportunities to oppose relations of power while reinforcing their limits within the confines of a disciplinary matrix.
Bareket Falk, Laura Brunton, Raffy Dotan, Charlotte Usselman, Panagiota Klentrou and Davie Gabriel
Ten prepubertal girls and 15 young women were tested for maximal torque, peak rate of torque development, electro-mechanical delay (EMD), and time to peak rate of torque development during isometric elbow flexion. Absolute peak torque (17.0 ± 7.7 vs. 40.5 ± 8.3 Nm) and peak rate of torque development (105.9 ± 58.6 vs. 297.2 ± 113.0 Nm·s−1) were lower in the girls (p < .05). Normalized to muscle cross sectional area, torque was similar (8.27 ± 2.74 vs. 8.44 ± 1.65 Nm·cm−2), as was peak rate of torque development, normalized to peak torque (6.21 ± 1.94 vs. 7.30 ± 2.26 Nm·s−1/Nm). Both, time to peak rate of torque development (123.8 ± 36.0 vs. 110.5 ± 52.6 ms) and EMD (73.2 ± 28.6 vs. 51.9 ± 25.6 ms), were longer in the girls, although EMD’s difference only approached statistical significance (p = .06). Age-related isometric strength differences in females appear to be mainly muscle-size dependent. However, the time to peak torque and EMD findings suggest differential motor-unit activation which may functionally manifest itself in fast dynamic contractions.
Janneke Lommertzen, Alexander M.J. van Zuijlen, Ruud G.J. Meulenbroek and Rob van Lier
The current study focused on the time course of the effects of the rod-and-frame illusion (RFI) on the kinematics of targeted forearm rotations. Participants were asked to reproduce perceived rod orientations by propelling a hand-held cylinder forward while rotating it to the target orientation. Rod and frame orientations were systematically varied, and cylinder rotations were normalized to time. Average realized cylinder orientations confirmed that when the frame orientation deviated from the vertical, a reproduction error occurred in the direction opposite to the direction of the frame tilt. In contrast, the perceived orientation of the stimulus rod was exaggerated relative to the vertical (i.e., reproduction errors were in the direction of the rod tilt). Furthermore, linear regression analyses for every normalized time sample showed that the rod and frame effects start simultaneously, but they reach their maximum effect at different points in time. We discuss the implications of our findings for current views on the effects of visual illusions on motor control.
Mostafa Yaghoubi, Mohamad Mahdi Esfehani, Hossein Asghar Hosseini, Yaser Alikhajeh and Sarah P. Shultz
The aim of this study was to compare muscle activity patterns between inexperienced and experienced water polo players while taking an overhead shot. The study was carried out with a group of 12 water polo players and an inexperienced group of 10 healthy participants. Signals were recorded by surface electromyography from six different muscles. The average and standard deviation of the normalized electrical activity, time to peak, time broadness, and muscle sequencing during the overhead shot were determined for each muscle in both groups and compared with each other. In water polo players, the normalized electrical activities of triceps brachii, pectoralis major, and wrist flexors were greater than other muscles, while in the inexperienced group the triceps brachii specifically played an important role. There was minimal activation of the middle deltoid and biceps brachii in water polo players. Increased times to peak and time broadness of muscles were found in the inexperienced group compared to experienced water polo players; this difference may be explained by different neuromuscular proprioception. Only experienced water polo players activated the observed muscles in a specific sequence, from proximal to distal. Therefore, coaches should emphasize smooth and quick transitions from proximal to distal segments, with less importance placed on individual muscle strengthening.