Based on the mechanostat theory and the muscle-bone hypothesis, a methodological assessment of the musculoskeletal status in health and disease should relate maximum muscle force in relation to bone mass and geometry. While useful (i.e. three-dimensional) measures of tibial bone parameters can be obtained by peripheral quantitative computed tomography (pQCT), intrinsic plantarflexor muscle force cannot be directly measured under in vivo condition in humans. Instead, tissue size, torque and ground reaction force have been used as proxy markers of intrinsic muscle force. However, most of these proxy markers are not or insufficiently representative of maximum force. Based on our recent research, we describe a novel approach for the assessment of the lower leg muscle-bone unit in health and disease. It incorporates multiple one-legged hopping (m1LH) to assess maximum voluntary ground reaction force acting on the forefoot (F_m1LH) and bone mineral content at the 14%-site of tibia length (vBMC_14%) as assessed by pQCT. Using the quantitative relationship between these two variables in conjunction with F_m1LH per body weight, we present a two-step quantitative diagnostic algorithm to discriminate between primary and secondary bone disorders in children and adults.

Objectives: To assess adaptations of the lower leg muscle-bone unit in 8- to 12-year-old children following a randomized controlled jumping exercise intervention for 9 months. Methods: Twelve boys and 10 girls (INT) performed a supervised jumping protocol during the first 10 min of their regularly scheduled physical education class twice a week, while 11 boys and 12 girls (CON) completed the regular curriculum. We assessed maximum voluntary ground reaction force during multiple one-legged hopping (F_m1LH), and tibial bone strength/geometry by peripheral quantitative computed tomography (pQCT) at the 4-, 14-, 38- and 66%-site pre, intermediate, and post intervention. Results: Whether increases in F_m1LH (+2.1% points, P=0.752), nor changes in bone strength/geometry (+1 to +3% points, 0.169<P<0.861), were significantly different for INT relative to CON. The relationship between F_m1LH and volumetric bone mineral content at the 14%-site (vBMC_14%) was very strong for both groups, pre and post intervention (0.51≤R²≤0.88). However, changes in F_m1LH and vBMC_14% were not correlated. Conclusions: In children, growth and exercise did not increase maximum muscle force and bone strength in proportion to each other, meaning that the adaptive processes were not tightly coupled or follow different time courses.

Objectives: The purpose of this study was to determine the effect of sports participation on cortical bone in the tibia. Methods: 53 female collegiate athletes (25 cross-country, 16 soccer, and 12 volleyball) and 20 inactive controls had the left distal 20% tibia scanned by pQCT. Cortical volumetric BMD (vBMD) was measured within the cortical shell at the anterior, posterior, medial, and lateral regions and standard deviations were calculated. Results: Total vBMD was greater in the control group (1161±5 mg/mm³) than each of the sports (p<0.05). Soccer players (1147±5 mg/mm³) had greater vBMD than volleyball players (1136±7 mg/mm³) (p<0.05), but similar to cross-country runners (1145±5 mg/mm³). Cortical thickness was greatest in soccer players (4.1±0.1 mm), while cross-country and control subjects (3.8±0.1 mm) had greater thickness than volleyball players (3.4±0.1 mm) (p<0.05). Periosteal circumference was greater in volleyball players (71±1.4 mm) than soccer, cross-country, and control subjects (68±0.9, 69±0.8, and 66±1 mm, respectively; all, p<0.05). vBMD variation within the cortical shell was greater among control subjects (70±6 mg/cm³) than each of the athlete groups, with soccer players having lower variation than cross country runners (within-person SD 36±6 mg/cm³ and 54±5 mg/cm³ respectively; p<0.05). Conclusion: These results indicate bone geometry and distribution within the cortical shell of the tibia varies depending upon sporting activities of young women.

A randomized controlled trial was conducted to compare the effect of a one-leg standing exercise and a chair-rising exercise on body balance in patients with locomotive disorders. Thirty ambulatory patients (mean age: 66.6 years) were randomly divided into two groups (n=15 in each group): a one-leg standing exercise group and a chair-rising exercise group. All the participants performed calisthenics of the major muscles, a tandem gait exercise, and a stepping exercise. The exercises were performed 3 days per week, and the study period was 5 months. Physical function was evaluated at baseline and at one-month intervals. No significant differences in the baseline characteristics were observed between the two groups. After the 5-month exercise program, the timed up and go, one-leg standing time, and tandem gait time improved significantly in the one-leg standing exercise group, while the walking time and chair-rising time in addition to above parameters improved significantly in the chair-rising exercise group. The improvements in the walking time, chair-rising time, and tandem gait time were significantly greater in the chair-rising exercise group than in the one-leg standing exercise group. The present study showed that the chair-rising exercise was more effective than the one-leg standing exercise for improving walking velocity and dynamic body balance.

The study investigated differences in skeletal muscle function between obese and non-obese children using a force platform. Forty obese children and adolescents (age range 8 to 18 years; 21 girls) and 40 age- and sex-matched controls performed two tests: (1) single two-legged jump, a countermovement jump for maximal height; (2) multiple one-legged hopping on the forefoot, a test of maximal force. In the single two-legged jump, obese subjects had higher absolute peak force (1.62 kN vs 1.09 kN) and peak power (2.46 kW vs 2.06 kW), but lower body weight-related peak force (2.10 vs 2.33) and lower peak power per body mass (30.9 W/kg vs 41.6 W/kg). Jump height (29.3 cm vs 37.5 cm) and maximal vertical velocity (1.92 ms^-1 vs 2.31 ms^-1) were reduced in obese children. In multiple one-legged hopping, obese subjects had 72% and 84% higher absolute peak force on the left and right foot, respectively. However, forces relative to body weight were 24% and 23% lower in the obese group than in the control group. In conclusion, obese children and adolescents have increased muscle force and power. This partly compensates for the effect of high body weight on muscle performance.

Objectives: This study evaluated the influence of diet-induced obesity on bone tissue quantity and quality in the proximal tibiae of growing mice and also examined the relationships between the serum total cholesterol, leptin, and adiponectin levels and trabecular and cortical bone mineral parameters. Methods: Six-week-old male C57BL/6J mice were divided into two groups; one received a control diet, and the other received a high-fat diet. After treatment for 4, 8, or 12 weeks, the bone quantity and quality were analyzed using peripheral quantitative computed tomography (pQCT), micro-computed tomography and histomorphometry. Results: In the early stages, trabecular bone density decreased with an increase in the number of adipocytes and the deterioration of trabeculae. In contrast, although cortical bone formation was slower in obese mice compared with control mice, bone formation on the periosteal surface increased with age. Serum leptin levels were correlated with trabecular, but not cortical bone density, whereas neither the adiponectin nor total cholesterol level was correlated with bone mass in mice with diet-induced obesity. Conclusions: We conclude that bone loss at these two sites is differentially regulated in mice. Furthermore, we demonstrate that serum leptin may be a useful indicator of risk for osteoporosis associated with diet-induced obesity.

Objective: Painless mechanical trauma is believed to induce neuroosteoarthropathy at the neuropathic foot in diabetes (diabetic Charcot-foot). To investigate pressure nociception at the diabetic foot, we measured the pain perception thresholds for deep pressure (DPPPT, using Algometer II^®) and cutaneous pressure (CPPPT, using calibrated monofilaments). Methods: In 24 diabetic patients with painless neuropathy (11 with a chronic, inactive Charcot-foot and a history of foot ulcer, and 13 control patients who never had an ulcer), and in 20 healthy subjects, CPPPT (at palmar and plantar digital skinfolds) and DPPPT (over musculus abductor pollicis, musculus hallucis longus, and over metacarpophalangeal and metatarsophalangeal joints) was measured. Results: At the hands, DPPPT and CPPPT were similar in patients and healthy subjects. At the feet, CPPPT was above the upper safety limit of measurement (512 mN) in 2/20 healthy subjects, and in 11/11 Charcot patients compared to 6/13 neuropathic controls (p=0.005). At the feet, median DPPPT was similar in all groups. In Charcot patients only, DPPPT was higher over metatarsophalangeal joint than over m. hallucis longus (p=0.048). Conclusion: Perception thresholds for cutaneous pressure pain, but not for deep pressure pain, may be extremely elevated at the diabetic neuropathic foot, and particularly at the Charcot-foot.