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Introduction: The assisted 6‐minute cycle test (A6MCT) distance was assessed in adults with muscular dystrophy (MD). Methods: Forty‐eight males, including those with Duchenne MD (DMD), limb‐girdle MD (LGMD), fascioscapulohumeral MD (FSHD), and Becker MD (BMD), as well as a group without MD (CTRL), completed handgrip strength (HGS), lung function [forced expiratory volume in 1 second (FEV1) and forced vital capacity (FVC)], body fat, and biceps thickness assessments. During the A6MCT, ventilation (Ve), oxygen uptake (Vo 2), carbon dioxide (Vco 2), and heart rate (HR) were recorded. Results: A6MCT and HGS were lower in MD than CTRL subjects. FEV1, FVC, and biceps thickness were lower in MD than CTRL; lower in DMD than BMD, LGMD, and FSHD; but were not different between BMD, LGMD, and FSHD. A6MCT correlated with HGS, FEV1, FVC, body fat, Vo 2, Vco 2, HR, and Ve (r = 0.455–0.708) in pooled BMD, LGMD, and FSHD participants. Discussion: A shorter A6MCT distance in adult males with MD was attributable to HGS and lung function. The A6MCT is appropriate for assessment of physical function in adults with MD. Muscle Nerve 58: 427–433, 2018

© 2018 Sims, Onambélé-Pearson, Burden, Payton and Morse. The disproportionate body mass and leg length of Achondroplasic individuals may affect their net oxygen consumption (VO 2 ) and metabolic cost (C) when walking at running compared to those of average stature (controls). The aim of this study was to measure submaximal VO 2 and C during a range of set walking speeds (SWS; 0.56-1.94 m·s-1, increment 0.28 m·s -1 ), set running speeds (SRS; 1.67-3.33 m·s -1 , increment 0.28 m·s -1 ) and a self-selected walking speed (SSW). VO 2 and C was scaled to total body mass (TBM) and fat free mass (FFM) while gait speed was scaled to leg length using Froude's number (Fr). Achondroplasic VO 2FFM x and VO 2FFM were on average 29 and 35% greater during SWS (P < 0.05) and 12 and 18% higher during SRS (P < 0.05) than controls, respectively. Achondroplasic CTBM and CFFM were 29 and 33% greater during SWS (P < 0.05) and 12 and 18% greater during SRS (P < 0.05) than controls, respectively. There was no difference in SSW VO 2TBM or VO 2FFM between groups (P > 0.05), but CTBM and CFFM at SSW were 23 and 29% higher (P < 0.05) in the Achondroplasic group compared to controls, respectively. VO 2TBM and VO 2FFM correlated with Fr for both groups (r = 0.984-0.999, P < 0.05). Leg length accounted for the majority of the higher VO 2TBM and VO 2FFM in the Achondroplasic group, but further work is required to explain the higher Achondroplasic CTBM and CFFM at all speeds compared to controls. New and Noteworthy: There is a leftward shift of oxygen consumption scaled to total body mass and fat free mass in Achondroplasic adults when walking and running. This is nullified when talking into account leg length. However, despite these scalars, Achondroplasic individuals have a higher walking and metabolic cost compared to age matched non-Achondroplasic individuals, suggesting biomechanical differences between the groups.

© 2017 Hicks, Onambele-Pearson, Winwood and Morse. Aim: The aim of this paper was to determine whether; (1) patella tendon stiffness, (2) the magnitude of vastus lateralis fascicle lengthening, and (3) eccentric torque correlate with markers of exercise induced muscle damage. Method: Combining dynamometry and ultrasonography, patella tendon properties and vastus lateralis architectural properties were measured pre and during the first of six sets of 12 maximal voluntary eccentric knee extensions. Maximal isometric torque loss and creatine kinase activity were measured pre-damage (-48 h), 48, 96, and 168 h post-damage as markers of exercise-induced muscle damage. Results: A significant increase in creatine kinase (883 ± 667 UL) and a significant reduction in maximal isometric torque loss (21%) was reported post-eccentric contractions. Change in creatine kinase from pre to peak significantly correlated with the relative change in vastus lateralis fascicle length during eccentric contractions (r = 0.53, p = 0.02) and with eccentric torque (r = 0.50, p = 0.02). Additionally, creatine kinase tended to correlate with estimated patella tendon lengthening during eccentric contractions (p < 0.10). However, creatine kinase did not correlate with resting measures of patella tendon properties or vastus lateralis properties. Similarly, torque loss did not correlate with any patella tendon or vastus lateralis properties at rest or during eccentric contractions. Conclusion: The current study demonstrates that the extent of fascicle strain during eccentric contractions correlates with the magnitude of the creatine kinase response. Although at rest, there is no relationship between patella tendon properties and markers of muscle damage; during eccentric contractions however, the patella tendon may play a role in the creatine kinase response following EIMD.

The aim of this investigation was to determine the effect of sustained monophasic oral contraceptive pill (MOCP) use on the in vivo passive stiffness of the gastrocnemius medialis (GM) muscle-tendon unit. Twenty four females volunteered for this study (age range 20-25 yrs); twelve participants had been taking the combined MOCP for a minimum of 12 months, and twelve participants, who had never taken the MOCP, formed a control group. Distal displacement of the GM myotendinous junction (MTJ) was measured during passive dorsiflexion at 2 Nm increments to 20 Nm, and at end range of motion using ultrasonography. In addition, GM MTJ displacement was measured at passive torques equivalent to 5, 10 and 15% of plantarflexion maximal voluntary contraction (MVC) torque, and relative to GM length. MOCP users had significantly greater GM MTJ displacement at all passive torques (P

Background: Short-term immobilisation results in a decrease in muscle size and strength. Ingestion of essential amino-acids (EAAs) stimulates net protein synthesis and supplementation is shown to improve lean body mass, strength and physical function, even without exercise. This study set out to determine whether EAA supplementation would attenuate immobilisation-induced changes in muscle characteristics. Methods: In n=16 healthy, habitually active participants from a mixed gender (n=10 females, 5 males) population aged 21 ± 3.1 years, the non-dominant arm was immobilised in a sling for 9 waking hours a day over 3 continuous weeks. Participants were randomly assigned to one of two groups: EAA or placebo treatment. The nutritional supplement treatment was consumed throughout the immobilisation period. Measures of muscle thickness (via b-mode ultrasonography), upper and lower arm girth (anthropometry), isometric torque (dynamometry), muscle activation (electromyography), and serum interleukin-6 (ELISA) were taken immediately before immobilisation (PRE) and immediately on removal of the sling (POST). Results: The decrease relative to baseline in arm girths was significantly greater with the placebo (-1.75% and -1.48%) than with the EAA supplement (-0.31% and -0.55%) in both the upper (p=0.01) and lower (p=0.045) arm. The direction of change in biceps sub-cutaneous adipose thickness differed significantly between the placebo and EAA supplements (-3.3% and 19.6%, respectively, p=0.03). Torque normalised by muscle thickness in the biceps decreased less in the EAA compared with the placebo group (-6% vs. -20%, P

The ability of a muscle to shorten and produce force is crucial for locomotion, posture, balance and respiration. During a contraction, myosin heads on the myosin filament propel the actin filament via ATP hydrolysis, resulting in shortening of the muscle and/or force generation. The maximal shortening velocity of a muscle fibre is largely determined by the myosin ATPase activity, while maximal force is primarily determined by the cross-sectional area. Since most muscles are pennate rather than parallel-fibred and work at different lever ratios, muscle architecture and joint-tendon anatomy has to be taken into account to obtain the force and velocity characteristics of a muscle. Additionally, the recruitment of agonistic and antagonistic muscles will contribute to the torque generated during a contraction. Finally, tendon compliance may impact on the rate of force rise and force generated if it is such that the muscle contraction proceeds in the ascending limb of the length-tension relation. Even when magnetic resonance imaging and ultrasound, combined with EMG and/or electrical stimulation, have been applied to relate changes in muscle contractile properties to alterations in muscle size and architecture during ageing and resistance training, a disproportionate change in muscle strength and size remains to be explained.

To explore the cause of higher skeletal muscle fatigue resistance in women than men, we used electrically evoked contractions (1-s on 1-s off, 30 Hz, 2 min), which circumvents motivational bias and allows examination of contractile properties. We compared 29 men (26.5 (7.0) yr) (mean (SD)) with 35 women (25.4 (7.6) yr). Strength of the quadriceps muscle was higher in men than women (P

Passive stretching is commonly used to increase limb range of movement prior to athletic performance but it is unclear which component of the muscle-tendon unit (MTU) is affected by this procedure. Movement of the myotendinous junction (MTJ) of the gastrocnemius medialis muscle was measured by ultrasonography in eight male participants (20.5 +/- 0.9 years) during a standard stretch in which the ankle was passively dorsiflexed at 1 deg s(-1) from 0 deg (the foot at right angles to the tibia) to the participants' volitional end range of motion (ROM). Passive torque, muscle fascicle length and pennation angle were also measured. Standard stretch measurements were made before (pre-) and after (post-) five passive conditioning stretches. During each conditioning stretch the MTU was taken to the end ROM and held for 1 min. Pre-conditioning the extension of the MTU during stretch was taken up almost equally by muscle and tendon. Following conditioning, ROM increased by 4.6 +/- 1.5 deg (17%) and the passive stiffness of the MTU was reduced (between 20 and 25 deg) by 47% from 16.0 +/- 3.6 to 10.2 +/- 2.0 Nm deg(-1). Distal MTJ displacement (between 0 and 25 deg) increased from 0.92 +/- 0.06 to 1.16 +/- 0.05 cm, accounting for all the additional MTU elongation and indicating that there was no change in tendon properties. Muscle extension pre-conditioning was explicable by change in length and pennation angle of the fascicles but post-conditioning this was not the case suggesting that at least part of the change in muscle with conditioning stretches was due to altered properties of connective tissue.