Kara A. Witzke

Effects of plyometric jump training on bone mass in adolescent girls.

PURPOSE The purpose of this study was to investigate the effects of 9 months of plyometric jump training on bone mineral content (BMC), lower extremity performance, and static balance in adolescent girls (aged 14.6 +/- 0.5 yr; 22.7 +/- 14.0 months past menarche). METHODS Exercisers (N = 25) trained 30-45 min, three times per week, performing various exercises using weighted vests (squats, lunges, calf raises) and plyometrics (hopping, jumping, bounding, and box depth jumps). The program was designed to load the lower extremities. Controls (N = 28), matched to exercisers for age and months past menarche, maintained their usual activities. The following were assessed at baseline and 9 months: BMC, strength by isokinetic dynamometry, power (Wingate), and static balance. RESULTS Repeated measures ANOVA revealed no significant differences between groups for BMC, nor were the changes in anthropometric or performance variables, analyzed by MANOVA, significant. In follow-up analyses, t-tests for independent samples revealed that both groups experienced a significant (P < 0.01) increase in percent change in bone mass compared to zero, for the whole body (mean: 3.7% exercisers, 3.6% controls), femoral neck (4.5% vs 2.4%), lumbar spine (L2-4) (6.6% vs 5.3%), and femoral shaft (3.4% vs 2.3%), but only the exercisers improved BMC of the greater trochanter (3.1% vs 1.9%). Furthermore, the exercise group significantly improved knee extensor strength (14.7% vs 7.3%) and medial/lateral balance (38.1% vs 9.5%), whereas the control group demonstrated no changes. The variety of lateral movement activities performed by the exercise group may have contributed to the differences observed between groups for greater trochanter bone mineral density (BMD), leg strength, and medial/lateral balance. CONCLUSION The trends observed in bone mass between groups suggest that plyometric jump training continued over a longer period of time during adolescent growth may increase peak bone mass.

Lean body mass and leg power best predict bone mineral density in adolescent girls.

PURPOSE We evaluated anthropometric and performance measures that best predict bone mineral density (BMD) and bone mineral content (BMC) in 54 adolescent girls (14.6 +/- 0.5 yr; 22.7 +/- 14.0 months past menarche). METHODS Whole body, femoral neck, greater trochanter, lumbar spine (L2-L4), and mid-femoral shaft BMD and BMC, and whole body bone-free lean mass and fat mass were assessed using DXA (Hologic QDR 1000/W). Knee extensor strength and leg power were assessed by isokinetic dynamometry and the Wingate Anaerobic Power Test, respectively. RESULTS Whole body lean mass was correlated with BMD at all bone sites (r = 0.45-0.77; P < 0.001) and was more highly correlated with bone at all sites than was body weight. Leg power was also associated with BMD at all sites (r = 0.41-0.67; P < 0.001), whereas leg strength correlated significantly with all sites (r = 0.41-0.53; P < 0.001) except the lumbar spine. Stepwise regression analyses revealed that 59% of the variance in whole body BMD was predicted by lean mass alone. No other variables, including fat mass, height, months past menarche, leg power, or leg strength, contributed additionally to the regression model. Similarly, lean mass was the only predictor of lumbar spine and femoral shaft BMD (R2 = 0.25, R2 = 0.37, respectively), while femoral neck and trochanteric BMD were best predicted by leg power (R2 = 0.38, R2 = 0.36, respectively). Similar but stronger models emerged using BMC as the outcome, with lean mass and leg power explaining the most variance in BMC values. CONCLUSION In this group of adolescent girls, lean body mass and leg power best predicted BMC and BMD of the whole body, lumbar spine, femoral shaft, and hip, which may suggest an important role for muscle mass development during growth to maximize peak bone density.

Loss of RAGE Defense: A Cause of Charcot Neuroarthropathy?

OBJECTIVE This study investigated the relationship between circulating soluble receptor for advanced glycation end products (sRAGE) and parameters of bone health in patients with Charcot neuroarthropathy (CNA). RESEARCH DESIGN AND METHODS Eighty men (aged 55.3 ± 9.0 years), including 30 healthy control subjects, 30 type 2 diabetic patients without Charcot, and 20 type 2 diabetic patients with stage 2 (nonacute) CNA, underwent evaluations of peripheral and autonomic neuropathy, nerve conduction, markers of bone turnover, bone mineral density, and bone stiffness of the calcaneus. RESULTS CNA patients had worse peripheral and autonomic neuropathy and a lower bone stiffness index than diabetic or control individuals (77.1, 103.3, and 105.1, respectively; P < 0.05), but no difference in bone mineral density (P > 0.05). CNA subjects also had lower sRAGE levels than control (162 vs. 1,140 pg/mL; P < 0.01) and diabetic (162 vs. 522 pg/mL; P < 0.05) subjects, and higher circulating osteocalcin levels. CONCLUSIONS CNA patients had significantly lower circulating sRAGE, with an accompanying increase in serum markers of bone turnover, and reduced bone stiffness in the calcaneus not accompanied by reductions in bone mineral density. These data suggest a failure of RAGE defense mechanisms against oxidative stress in diabetes. Future studies should determine if medications that increase sRAGE activity could be useful in mitigating progression to CNA.

Diabetic neuropathy in older adults.

Diabetic neuropathies (DN) encompass a wide range of nerve abnormalities and are common, with prevalence rates reported between 5–100% depending on the diagnostic criteria [1–3]. Diabetic neuropathies affect both peripheral and autonomic nervous systems and cause considerable morbidity and mortality in both Type 1 and Type 2 diabetic patients. Diabetic neuropathies are the most common forms of neuropathy, they account for more hospitalizations than all other diabetic complications combined, and are responsible for 50–75% of non-traumatic amputations [4,5]. In older adults with diabetes, peripheral neuropathies are especially troublesome due to their detrimental effects on stability, sensorimotor function, gait, and activities of daily living [6–8]. In this review, we present and discuss the most recent approaches to the treatment of the common forms of diabetic neuropathy, including symmetric, focal and diffuse neuropathies (Table 1, Fig. 1). We will also provide the reader with algorithms for recognition and management of common pain and entrapment syndromes, and a global approach to recognition of syndromes requiring specialized treatments based upon our improved understanding of their etiopathogenesis. A comprehensive evaluation of autonomic neuropathy is beyond the scope of this review, but the reader is referred to two excellent reviews on this topic [9,10].

Chronic activity-based therapy does not improve body composition, insulin-like growth factor-I, adiponectin, or myostatin in persons with spinal cord injury

Abstract Spinal cord injury (SCI) induces dramatic changes in body composition including reductions in fat-free mass (FFM) and increases in fat mass (FM). Objective To examine changes in body composition in response to chronic activity-based therapy (ABT) in persons with SCI. Design Longitudinal exercise intervention. Methods Seventeen men and women with SCI (mean age = 36.1 ± 11.5 years) completed 6 months of supervised ABT consisting of load bearing, resistance training, locomotor training, and functional electrical stimulation. At baseline and after 3 and 6 months of ABT, body weight, body fat, and FFM were assessed using dual-energy X-ray absorptiometry, and fasting blood samples were obtained to assess changes in insulin-like growth factor-I (IGF-I), adiponectin, and myostatin. Results Across all subjects, there was no change (P > 0.05) in body weight, percent body fat, or FFM of the leg, arm, or trunk, whereas whole-body FFM declined (P = 0.02, 50.4 ± 8.4 to 49.2 ± 7.4 kg). No changes (P = 0.21–0.41) were demonstrated in IGF-I, adiponectin, or myostatin during the study. Conclusions Chronic ABT focusing on the lower extremity does not slow muscle atrophy or alter body fat, body mass, or regional depots of FFM in persons with SCI. Further, it does not induce beneficial changes in adiponectin, myostatin, or IGF-I. Alternative exercise-based therapies are needed in SCI to reverse muscle atrophy and minimize the onset of related health risks.

Charcot Neuroarthropathy may be the RAGE

Charcot neuroarthropathy (CNA) is a degenerative bone disease of unknown origin that occurs in the ankle and midfoot. While not exclusive to patients with diabetes, CNA will develop in about 0.1-2.5% of those with diabetes [1,2]. Recent work has focused on understanding the common link between inflammation induced by oxidative stress and the ensuing accumulation of advanced glycation end products (AGEs) leading to impaired bone mineral matrix mineralization and reduced bone strength in CNA. Collagen cross-linking is important for bone strength but non-enzymatic crosslinking results in an accumulation of AGEs in bone, accelerated by oxidative stress. AGEs stimulate apoptosis of osteoblastic cells mediated through RAGE, the pattern recognition receptor for AGE. AGE-RAGE interactions alter intracellular signaling via pro-inflammatory cytokines that further propagate diabetic complications. sRAGE is a soluble form of RAGE that competes with membrane-bound RAGE receptors for AGEs and functions as a decoy to “mop up” circulating AGEs, preventing them from binding to RAGE and causing an inflammatory cascade. A reduction in serum sRAGE is associated with increased vascular risk factors in diabetes mellitus and the metabolic syndrome. Recently, it was shown that bone specimens removed from CNA patients display reduced trabecular number and the presence of woven bone. We have previously shown derangements in collagen structure of the Achilles tendon and reduced calcaneal bone stiffness in CNA patients correlated with a marked reduction in circulating sRAGE. These results suggest a relationship between impaired AGE defense, bone turnover, and reduced bone quality in CNA. Based on limited studies relating RAGE to bone status and a few animal studies using sRAGE administration to interfere with RAGE expression, we speculate that sRAGE administration may have potential to interrupt osteoclastic activation in those who lack adequate endogenous production such as patients with CNA.

Loss of Receptor for Advanced Glycation End Products (RAGE) Defense A cause of Charcot neuroarthropathy

OBJECTIVE This study investigated the relationship between circulating soluble receptor for advanced glycation end products (sRAGE) and parameters of bone health in patients with Charcot neuroarthropathy (CNA). RESEARCH DESIGN AND METHODS Eighty men (aged 55.3 ± 9.0 years), including 30 healthy control subjects, 30 type 2 diabetic patients without Charcot, and 20 type 2 diabetic patients with stage 2 (nonacute) CNA, underwent evaluations of peripheral and autonomic neuropathy, nerve conduction, markers of bone turnover, bone mineral density, and bone stiffness of the calcaneus. RESULTS CNA patients had worse peripheral and autonomic neuropathy and a lower bone stiffness index than diabetic or control individuals (77.1, 103.3, and 105.1, respectively; P < 0.05), but no difference in bone mineral density (P > 0.05). CNA subjects also had lower sRAGE levels than control (162 vs. 1,140 pg/mL; P < 0.01) and diabetic (162 vs. 522 pg/mL; P < 0.05) subjects, and higher circulating osteocalcin levels. CONCLUSIONS CNA patients had significantly lower circulating sRAGE, with an accompanying increase in serum markers of bone turnover, and reduced bone stiffness in the calcaneus not accompanied by reductions in bone mineral density. These data suggest a failure of RAGE defense mechanisms against oxidative stress in diabetes. Future studies should determine if medications that increase sRAGE activity could be useful in mitigating progression to CNA.

Loss of Receptor for Advanced Glycation End Products (RAGE) Defense

OBJECTIVE This study investigated the relationship between circulating soluble receptor for advanced glycation end products (sRAGE) and parameters of bone health in patients with Charcot neuroarthropathy (CNA). RESEARCH DESIGN AND METHODS Eighty men (aged 55.3 ± 9.0 years), including 30 healthy control subjects, 30 type 2 diabetic patients without Charcot, and 20 type 2 diabetic patients with stage 2 (nonacute) CNA, underwent evaluations of peripheral and autonomic neuropathy, nerve conduction, markers of bone turnover, bone mineral density, and bone stiffness of the calcaneus. RESULTS CNA patients had worse peripheral and autonomic neuropathy and a lower bone stiffness index than diabetic or control individuals (77.1, 103.3, and 105.1, respectively; P < 0.05), but no difference in bone mineral density (P > 0.05). CNA subjects also had lower sRAGE levels than control (162 vs. 1,140 pg/mL; P < 0.01) and diabetic (162 vs. 522 pg/mL; P < 0.05) subjects, and higher circulating osteocalcin levels. CONCLUSIONS CNA patients had significantly lower circulating sRAGE, with an accompanying increase in serum markers of bone turnover, and reduced bone stiffness in the calcaneus not accompanied by reductions in bone mineral density. These data suggest a failure of RAGE defense mechanisms against oxidative stress in diabetes. Future studies should determine if medications that increase sRAGE activity could be useful in mitigating progression to CNA.

COLLEGIATE WRESTLERS DISPLAY HIGH BONE MASS AT THE HIP COMPARED WITH AGE-MATCHED NORMALS

Abstract 1177 Exercises which impose unique, high-impact loads on the skeleton andhigh muscular acceleration/deceleration patterns may be morebeneficial to bone than are customary loads. Wrestling imposes thesetypes of forces on the skeleton, particularly at the hip. We evaluatedbone mineral density (BMD) at pre-season and change in BMD over atraining season in NCAA wrestlers. Twenty-six males (age 21.3 ± 2.8yrs; 77.8 ± 11.9 kg; 175.4 ± 8.1 cm; wrestled 11 ± 3 yrs) were scanned(whole body, spine (L2-L4), proximal femur) by DXA (Hologic QDR1000/W) at the pre-season and eleven returned for follow-up scansimmediately after NCAA finals. The most striking finding was theuniformly high BMD at the spine and hip, despite only moderate valuesfor the whole body compared to age-matched normals supplied by theDXA manufacturer. Furthermore, BMD values at the hip regions weresignificantly higher than at the spine (t-test). (Table)The high-impact forces transmitted to the hip during wrestling appearto be of substantial magnitude to produce a long-term osteogenicresponse. Although changes over 5 months were significant at thewhole body and lumbar spine, but not the hip, these results arepreliminary and require longer follow-up with a larger sample size andcomparison with a control sample.American College of Sports Medicine; 46th Annual Meeting;Washington State; Convention & Trade Center; June 2-5, 1999The abstracts contained herein were prepared by the authors and thenprinted by photo-offset without correction. The accuracy, form ofcitation, designation, nomenclature, and the like, all remain theresponsibility of the author. Readers should note that the appearanceof an abstract does not imply future publication of a regular scientificmanuscript.E-26 POSTER BONE DENSITY & EXERCISE