A spatio-temporal and kinematic description of self-selected walking in adults with Achondroplasia

© 2020 Background: Achondroplasia is characterised by a shorter appendicular limb to torso ratio, compared to age matched individuals of average stature (controls). Despite the well documented shorter leg length of individuals with compared to controls, there are few complete descriptions of gait kinematics reported for the population. Aim: The aim of this study was to report the spatio-temporal and kinematic characteristics of self-selected walking (SSW) in a group with Achondroplasia (N = 10) and age matched group without Achondroplasia (controls, N = 17). Method: Whole body 3D analysis of both groups was conducted using a 14 camera VICON system. Spatio-temporal and kinematic variables were determined through a Plug-in-Gait model. SSW was obtained from an average of three trials equating to a total of ∼120 m walking. Results: The group with Achondroplasia were 23 % slower (P < 0.001), had a 29 % shorter stride length (P < 0.001) and a 13 % higher stride frequency (P < 0.001) compared to controls. There were no differences in time normalised temporal measures of left toe off (P = 0.365), right heel contact (P = 0.442) or the duration of double support (P = 0.588) between groups. A number of discrete joint kinematic differences existed between groups, resulting in the group with Achondroplasia having more ‘flexed’ lower limbs than controls throughout the gait cycle. Conclusion: Differences in absolute spatio-temporal variables between groups is likely due to the shorter leg length of the group with Achondroplasia, while their more flexed position of the lower limbs may facilitate toe-clearance during the swing phase

Heterogeneity of capillary spacing in the hypertrophied plantaris muscle from young-adult and old rats.

Item does not contain fulltextHeterogeneity of capillary spacing may affect tissue oxygenation. The determinants of heterogeneity of capillary spacing are, however, unknown. To investigate whether 1) impaired angiogenesis and increased heterogeneity of capillary spacing delays development of hypertrophy during aging and 2) heterogeneity of capillary spacing is determined by variations in fiber size we overloaded the left m. plantaris in young-adult (5-month-old) and old (25-month-old) rats for 1, 2 or 4 weeks by denervation of synergists, while the right leg served as an internal control. Fiber size, capillary density and capillary to fiber ratio were similar in control young-adult and old muscles. The time course and degree of hypertrophy were similar at both ages, indicating that in rats up to the age of 25 months the hypertrophic response is maintained. The variation in fiber size and heterogeneity of capillary spacing were, however, larger in old than young-adult muscles, larger in the superficial than the deep region of the muscle, and correlated significantly (R = 0.558; P < 0.001). This suggests that part of the heterogeneity of capillary spacing is due to heterogeneity in fiber size and may reflect that morphological constraints for positioning of capillaries partly determines heterogeneity of capillary spacing in muscle

Effects of smoking on tibial and radial bone mass and strength may diminish with age.

PURPOSE: The purpose of the study was to assess the effect of cigarette smoking on indicators of bone strength across a wide age range, controlling for physical activity and neuromuscular performance. METHODS: We conducted a cross-sectional study with 41 smokers (mean age +/- SD, 41.0 +/- 16.1 yr) and 53 nonsmokers (47.5 +/- 18.2 yr) of both sexes. Bone strength indicators (BSI) were assessed in the lower leg and forearm by peripheral quantitative computed tomography along with physical activity, muscle cross-sectional area, and maximal voluntary muscle force. RESULTS: Physical activity level and muscle cross-sectional area of the leg and arm were similar in smokers and nonsmokers. Although trabecular volumetric bone mineral density and epiphyseal bone mineral content, both indicators of BSI, decreased with age in the nonsmokers' tibia (P < 0.001), this was not observed in the smokers (interaction age x smoking: P = 0.014 and P = 0.032 for density and content, respectively). Regression coefficients were nonsignificant in nonsmokers, whereas coefficients in smokers were -1.24 mg/cm x yr [95% confidence interval (CI) = -2.16-0.33; P = 0.01] for content and -1.20 mg/cm(3) x yr (95% CI = -1.76-0.62; P < 0.001) for trabecular density. The BSI values in the smokers were independent of their smoking history (r(2) = 0.000-0.021), and no effects of sex were observed in the smoking-related differences in BSI. CONCLUSIONS: Smoking compromises bone strength by diaphyseal marrow cavity expansion and epiphyseal trabecular bone content reductions. These effects seem to wane with age. The causes of the attenuated effect of smoking on bone at old age remain enigmatic but might be linked to an interaction between the smoke-related factors and senescence processes affecting bone

Carbon monoxide inhalation reduces skeletal muscle fatigue resistance.

AIM: To determine whether inhalation of carbon monoxide (CO), resulting in carboxyhaemoglobin (COHb) levels observed in smokers, had an effect on muscle fatigue during electrically evoked and voluntary muscle contractions. METHODS: Young non-smoking males inspired CO from a Douglas bag until their COHb level reached 6%. During the control condition the same participants inspired ambient air from a Douglas bag for 6 min. Fatigue was assessed as the decline in torque in isometric knee extensions, during 2 min of electrically evoked contractions (30 Hz, 1 s on, 1 s off) and during 2 min of maximal isometric voluntary contractions (1 s on, 1 s off). A fatigue index (FI) was calculated as the ratio of final torque : initial torque. Time to peak torque (TPT) and half relaxation time ((1/2)RT) were also determined for the electrically evoked contractions. RESULTS: The FI during both the voluntary fatigue test (control: 0.80 +/- 0.09 vs. CO: 0.70 +/- 0.08; mean +/- SD) and that of the fatigue test with electrically evoked contractions (control: 0.61 +/- 0.09 vs. CO: 0.53 +/- 0.12) was significantly lower after CO inhalation than after inhalation of ambient air (P < 0.05). There was, however, no effect of CO on the changes in TPT or (1/2)RT during the fatigue test. CONCLUSION: Carbon monoxide inhalation resulting in COHb levels found in smokers has an acute impact on the ability of the muscle to resist fatigue