In-season strength maintenance training increases well-trained cyclists’ performance

We investigated the effects of strength maintenance training on thigh muscle cross-sectional area (CSA), leg strength, determinants of cycling performance, and cycling performance. Well-trained cyclists completed either (1) usual endurance training supplemented with heavy strength training twice a week during a 12-week preparatory period followed by strength maintenance training once a week during the first 13 weeks of a competition period (E + S; n = 6 [♂ = 6]), or (2) usual endurance training during the whole intervention period (E; n = 6 [♂ = 5, ♀ = 1]). Following the preparatory period, E + S increased thigh muscle CSA and 1RM (p < 0.05), while no changes were observed in E. Both groups increased maximal oxygen consumption and mean power output in the 40-min all-out trial (p < 0.05). At 13 weeks into the competition period, E + S had preserved the increase in CSA and strength from the preparatory period. From the beginning of the preparatory period to 13 weeks into the competition period, E + S increased peak power output in the Wingate test, power output at 2 mmol l⁻¹ [la⁻], maximal aerobic power output (W _max), and mean power output in the 40-min all-out trial (p < 0.05). The relative improvements in the last two measurements were larger than in E (p < 0.05). For E, W _max and power output at 2 mmol l⁻¹ [la⁻] remained unchanged. In conclusion, in well-trained cyclists, strength maintenance training in a competition period preserved increases in thigh muscle CSA and leg strength attained in a preceding preparatory period and further improved cycling performance determinants and performance.     

Region-specific differences in Achilles tendon cross-sectional area in runners and non-runners

The present study examined the cross-sectional area (CSA) of the Achilles tendon in subjects who repeatedly exposed their tendons to large loads (habitual runners) compared to control subjects (non-runners). Six male habitual runners [36 (7) years, 70.9 (4.4) kg and 1.84 (0.05) m, ±SD] who had performed distance running (~80 km per week) for the last 5 years were compared to six non-runners [34 (3) years, 81.2 (8.7) kg and 1.81 (0.02) m, ±SD]. Tendon CSA was obtained from MR images obtained with the ankle in a neutral position (90°). The most proximal aspect of the tuberosity of calcaneus was used as a landmark to standardize the levels of images: the most distal image (1) was obtained 10 mm above the proximal tuberosity of calcaneus, and the most proximal image (7) was obtained 70 mm above the proximal tuberosity of calcaneus. There was a significant difference in CSA along the length of the tendon both in runners (P<0.001) and non-runners (P<0.01). In non-runners and runners the CSA of the most distal part was 51% and 85% greater than the most proximal part of the tendon, respectively. Furthermore, there was a difference in tendon CSA between the groups, such that runners had a greater CSA (36%) than non-runners at the most distal part of the tendon (P<0.05). The greater CSA in the distal tendon may reflect differences in structural properties along the length of the human Achilles tendon, while the greater CSA in runners compared to non-runners may indicate a region-specific hypertrophy in response to the habitual loading of running.     

Higher prevalence of exercise-associated hyponatremia in female than in male open-water ultra-endurance swimmers: the 'Marathon-Swim' in Lake Zurich

We investigated the prevalence of exercise-associated hyponatremia (EAH) in 25 male and 11 female open-water ultra-endurance swimmers participating in the ‘Marathon-Swim’ in Lake Zurich, Switzerland, covering a distance of 26.4 km. Changes in body mass, fat mass, skeletal muscle mass, total body water, urine specific gravity, plasma sodium concentration [Na⁺] and haematocrit were determined. Two males (8%) and four females (36%) developed EAH where one female was symptomatic with plasma sodium [Na⁺] of 127 mmol/L. Body mass and plasma [Na⁺] decreased (p < 0.05). The changes in body mass correlated in both male and female swimmers to post-race plasma [Na⁺] (r = −0.67, p = 0.0002 and r = −0.80, p = 0.0034, respectively) and changes in plasma [Na⁺] (r = −0.68, p = 0.0002 and r = −0.79, p = 0.0039, respectively). Fluid intake was neither associated with changes in body mass, post-race plasma [Na⁺] or the change in plasma [Na⁺]. Sodium intake showed no association with either the changes in plasma [Na⁺] or post-race plasma [Na⁺]. We concluded that the prevalence of EAH was greater in female than in male open-water ultra-endurance swimmers.     

The histology and histomorphometry of umbilical cord cross section in preeclampsia and normal pregnancies: a comparative study

ABSTRACT

The umbilical cord is the connecting link between the mother and the fetus and its morphology is an indicator of fetal well-being. Preeclampsia is a disorder of pregnancy associated with new-onset hypertension, which occurs most often after 20 weeks of gestation. There are structural differences in the umbilical cord of normotensive and hypertensive pregnant women. This research aimed to study the histology and histomorphometry of umbilical cord areas in preeclampsia and compare the parameters with normal uncomplicated pregnancies of gestational age 37–40 weeks. A total of 70 umbilical cords were studied from preeclampsia (n = 35) and normal (n = 35) pregnancies. The parameters studied included cross-sectional areas (CSA) of umbilical cord, umbilical vein lumen, umbilical vein wall, umbilical artery lumen, umbilical artery wall, and Wharton’s jelly, including the presence of edema in the vessel walls and Wharton’s jelly and basement membrane thickening. The mean umbilical cord CSA was significantly higher in preeclampsia (p = 0.014). The mean umbilical artery lumen CSA was significantly lower than the normal pregnancy cords (p = 0.006). The mean Wharton’s jelly CSA in preeclampsia was significantly higher than the normal pregnancy cords (p = 0.004). The parameters for umbilical vein lumen CSA, umbilical vein wall CSA, and umbilical artery wall CSA did not show any significant difference. Histological findings were edema (p < 0.001) and thickened basement membranes (p < 0.0001) were considered significant.     

Total blood volume in endurance-trained postmenopausal females: relation to exercise mode and maximal aerobic capacity

We have recently shown that postmenopausal female distance runners demonstrate elevated levels of blood volume compared with sedentary healthy peers. We also found a strong positive relation between blood volume and maximal oxygen consumption. In young adult males, endurance exercise training increases blood volume when performed in the upright, but not in the supine body position. Based on these observations, we hypothesized that among postmenopausal females, the elevation in blood volume would be absent or attenuated in women who train in the horizontal vs. upright body position, and that the lower blood volume in the former would be associated with lower maximal aerobic capacity. Thus, we measured supine resting plasma and total blood volumes (Evans blue dye) and maximal oxygen consumption in postmenopausal women: 10 sedentary controls, 10 swimmers and 10 runners matched for age (60 ± 2; 59 ± 2; 58 ± 2 years, mean ± SE) and hormone replacement use (5 per group). The swimmers and runners were further matched for training volume (4.5 ± 0.2 vs. 4.8 ± 0.6 h week^–1), relative performance (78 ± 5 vs. 75 ± 3% of age-group world record) and fat-free mass (45.5 ± 0.8 vs. 44.9 ± 1.5 kg). Total blood volume and maximal oxygen consumption were highest in the runners (81.2 ± 4; 52.4 ± 3 mL kg^–1, respectively) and progressively lower in the swimmers (68.8 ± 3; 44.2 ± 2) and controls (59.2 ± 2; 37.9 ± 2; all P < 0.05). In the pooled population, blood volume was positively related to maximal oxygen consumption (r= 0.72, P < 0.0001). We conclude that in endurance-trained postmenopausal females matched for training volume and competitive performance: (1) blood volume is lower in those who train in the horizontal (swimmers) compared with the upright position (runners); (2) the lower blood volume is associated with a lower maximal aerobic capacity. Nevertheless, blood volume and maximal oxygen consumption are higher in postmenopausal women who train in the horizontal position than in sedentary controls.     

Effect of heavy strength training on thigh muscle cross-sectional area, performance determinants, and performance in well-trained cyclists

The purpose of this study was to investigate the effect of heavy strength training on thigh muscle cross-sectional area (CSA), determinants of cycling performance, and cycling performance in well-trained cyclists. Twenty well-trained cyclists were assigned to either usual endurance training combined with heavy strength training [E + S; n = 11 (♂ = 11)] or to usual endurance training only [E; n = 9 (♂ = 7, ♀ = 2)]. The strength training performed by E + S consisted of four lower body exercises [3 × 4–10 repetition maximum (RM)], which were performed twice a week for 12 weeks. Thigh muscle CSA, maximal force in isometric half squat, power output in 30 s Wingate test, maximal oxygen consumption (VO_2max), power output at 2 mmol l⁻¹ blood lactate concentration ([la⁻]), and performance, as mean power production, in a 40-min all-out trial were measured before and after the intervention. E + S increased thigh muscle CSA, maximal isometric force, and peak power in the Wingate test more than E. Power output at 2 mmol l⁻¹ [la⁻] and mean power output in the 40-min all-out trial were improved in E + S (P < 0.05). For E, only performance in the 40-min all-out trial tended to improve (P = 0.057). The two groups showed similar increases in VO_2max (P < 0.05). In conclusion, adding strength training to usual endurance training improved determinants of cycling performance as well as performance in well-trained cyclists. Of particular note is that the added strength training increased thigh muscle CSA without causing an increase in body mass.     

Effects of plyometric training on both active and passive parts of the plantarflexors series elastic component stiffness of muscle-tendon complex

The aims of this study were to determine the effects of plyometric training on both active and passive parts of the series elastic component (SEC) stiffness, and on geometrical parameters [i.e., muscle architecture, muscle and tendon cross-sectional area (CSA)] of the plantarflexors muscle–tendon complex to assess possible specific adaptations of the elastic properties. Nineteen subjects were randomly divided into a trained group and a control group. Active and passive components of the SEC stiffness were determined using a fast stretch during submaximal voluntary isometric plantarflexor activity. Geometrical parameters of the triceps surae muscles and the Achilles tendon were determined using ultrasonography. A significant increase in the passive component of the SEC stiffness was found (p < 0.05). In contrast, a significant decrease in the active part of the SEC stiffness was observed (p < 0.05). No significant changes in plantarflexor muscles CSA, architecture and Achilles tendon CSA were seen (p > 0.05). Thus, plyometric training led to specific adaptations within each part of the SEC. Theses adaptations could increase both the efficiency of the energy storage–recoil process and muscular tension transmission leading to an increase in jump performances.     

Endurance rather than sprint running training increases left ventricular wall thickness in female athletes

Competitive athletics is often associated with moderate left ventricular (LV) hypertrophy. The aim of this study was to shed more light on the extent and type of cardiac hypertrophic response to different athletic conditioning in females. Standard two-dimensional M-mode and Doppler echocardiography was performed at rest in Caucasian female sprinters (n = 10) and long-distance runners (n = 10) of similar age (range 16–34 years), training experience (5–18 years) and competitive level, and in age-matched healthy female sedentary controls (n = 10). No differences in echocardiographic parameters were detected between female sprinters and sedentary controls (p > 0.05). Interventricular septum and LV wall (p < 0.05) were thicker, and LV mass was greater (p < 0.01) in long-distance runners as compared with sprinters or sedentary controls. Absolute LV diameter was not increased in long-distance runners (p > 0.05), though relative LV diameter was higher in long-distance runners as compared to sprinters (p < 0.05). As compared with controls, relative wall thickness (the sum of LV wall thickness and interventricular septum thickness divided by LV diameter) was higher (p = 0.004) in long-distance runners. Neither systolic nor diastolic LV parameters were different among the groups (p > 0.05). In conclusion, sprint running training has not been found to induce alterations in cardiac morphology or function at rest in female athletes. Cardiac mass in female long-distance runners is higher mainly due to myocardial wall thickening, while integral myocardial function at rest is not affected as a consequence of either this hypertrophy or sprint training.     

Water polo is associated with an apparent redistribution of bone mass and density from the lower to the upper limbs

The bone response to exercise is site-specific and load-dependent. Recent evidence suggests that an inverse relationship may exist between loaded and unloaded sites, such that the former may benefit at the expense of the latter. The present study examined this possibility in 48 males (21 water polo players, 12 handball players, and 15 sedentary controls). Water polo and handball are alike with respect to the active loading of the upper limbs during overhead throwing; however, the weight-supporting environment of water polo removes the weight-bearing effect from the lower limbs. Bone mineral content (BMC), bone projected area (Ap), and areal bone mineral density (aBMD) of the total body and of various subregions were determined by dual-energy X-ray absorptiometry. After adjusting for age, height, and weight, water polo players had higher arms BMC, Ap, and aBMD (by 22.2, 11.1, and 10.5%, respectively; P < 0.05), but lower legs aBMD (−6.3%; P < 0.05) relative to controls. On the contrary, compared to controls, handball players had higher BMC (from 11.8 to 24.3%), Ap (from 5.2 to 11.7%), and aBMD (from 6.4 to 11.9%) for the total body at all sites. Water polo athletes had increased arms and decreased legs aBMD ratios (regional-to-total) than either handball players or sedentary subjects (P < 0.001). Water polo is associated with an apparent redistribution of bone mass and density from the lower to the upper limbs, with no major effects on the rest of the body.     

Effects of strength,endurance and combined training on muscle strength,walking speed and dynamic balance in aging men

The aim of this study was to examine effects of 21-week twice weekly strength (ST), endurance (ET) and combined (ST + ET 2 + 2 times a week) (SET) training on neuromuscular, endurance and walking performances as well as balance. 108 healthy men (56.3 ± 9.9 years) were divided into three training (ST; n = 30, ET; n = 26, SET; n = 31) groups and controls (C n = 21). Dynamic 1RM and explosive leg presses (1RMleg, 50%1RMleg), peak oxygen uptake using a bicycle ergometer (VO_2peak), 10 m loaded walking time (10WALK) and dynamic balance distance (DYND) were measured. Significant increases were observed in maximal 1RMleg of 21% in ST (p < 0.001) and 22% in SET (p < 0.001) and in explosive 50%1RMleg of 7.5% in ST (p = 0.005) and 10.2% in SET (p < 0.001). VO_2peak increased by 12.5% in ET (p = 0.001) and 9.8% in SET (p < 0.001). Significant decreases occurred in 10WALK in ST (p < 0.001) and SET (p = 0.003) and also in DYND of −10.3% in ST (p = 0.002) and −8% in SET (p = 0.028). The changes in C remained minor in all variables. In conclusion, ST and SET training produced significant improvements in maximal and explosive strength, walking speed and balance without any interference effect in SET. Significant but moderate relationships were observed between strength and dynamic balance and walking speed, while no corresponding correlations were found in the ET group.     

Association between ACE D allele and elite short distance swimming

The influence of ACE gene on athletic performance has been widely explored, and most of the published data refers to an I/D polymorphism leading to the presence (I allele) or absence (D allele) of a 287-bp sequence in intron 16, determining ACE activity in serum and tissues. A higher I allele frequency has been reported among elite endurance athletes, while the D allele was more frequent among those engaged in more power-orientated sports. However, on competitive swimming, the reproducibility of such associations is controversial. We thus compared the ACE genotype of elite swimmers with that of non-elite swimming cohort and of healthy control subjects. We thus sought an association of the ACE genotype of elite swimmers with their competitive distance. 39 Portuguese Olympic swimming candidates were classified as: short (<200 m) and middle (400–1,500 m) distance swimmers, respectively. A group of 32 non-elite swimmers were studied and classified as well, and a control group (n = 100) was selected from the Portuguese population. Chelex 100 was used for DNA extraction and genotype was determined by PCR-RFLP methods. We found that ACE genotype distribution and allelic frequency differs significantly by event distance only among elite swimmers (P ≤ 0.05). Moreover, the allelic frequency of the elite short distance swimmers differed significantly from that of the controls (P = 0.021). No associations were found between middle distance swimmers and controls. Our results seem to support an association between the D allele and elite short distance swimming.     

Oxidative stress, inflammation, and muscle soreness in an 894-km relay trail run

We describe the effects of multi-day relay trail running on muscle soreness and damage, and systemic immune, inflammatory, and oxidative responses. 16 male and 4 female athletes ran 894 km in 47 stages over 95 h, with mean (SD) 6.4 (1.0) stages per athlete and 19.0 (1.7) km per stage. We observed post–pre run increases in serum creatine kinase (qualified effect size extremely large, p = 0.002), IL-6 (extremely large, p < 0.001), urinary 8–isoprostane/creatinine (extremely large, p = 0.04), TNF-α (large, p = 0.002), leukocyte count (very large, p < 0.0001) and neutrophil fraction (very large, p < 0.001); and reductions in hemoglobin (moderate, p < 0.001), hematocrit (moderate, p < 0.001), and lymphocyte fraction (trivial, p < 0.001). An increase in ORAC total antioxidant capacity (TAC, small, p = 0.3) and decrease in urinary 8-OHdG/creatinine (small, p = 0.1) were not statistically significant. During the run, muscle soreness was most frequent in the quadriceps. The threshold for muscle pain (pain-pressure algometry) in the vastus lateralis and gastrocnemius was lower post-run (small, p = 0.04 and 0.03). Average running speed was correlated with algometer pain and leukocyte count (large, r = 0.52), and TAC was correlated with IL-6 (very large, r = 0.76) and 8-isoprostane/creatinine (very large, r = −0.72). Multi-day stage-racing increases inflammation, lipid peroxidation, muscle damage and soreness without oxidative DNA damage. High TAC is associated with reduced exercise-induced lipid peroxidation, but is not related to immune response or muscle damage.     

The association of emotional well-being and marital status with treatment adherence among patients with hypertension

We were interested in examining the relationship between psychosocial factors and hypertension-related behaviors. We hypothesized that lower emotional well-being and unmarried status would be related to higher BP, poorer medication adherence, greater difficulty adhering to diet and exercise, and current smoking. In a cross-sectional design, 636 hypertensive patients completed the Mental Component Summary (MCS) Scale of the SF-12 and rated their difficulty with adherence to diet, exercise, and medication-taking. In logistic regression analyses, lower MCS scores were associated with difficulty adhering to diet (OR = 0.97, p < .05) and exercise (OR = 0.97, p < .01), and current smoking status (OR = 0.98, p < .05). Being married was associated with higher probability of medication adherence (OR = 1.66, p < .01) and a lower probability of being a current smoker (OR = 0.34, p < .0001). Neither MCS scores nor being married were related to BP levels in adjusted analyses. Results emphasize the importance of assessing psychosocial factors to optimize hypertension treatment.     

Effects of vibration training on bone metabolism: results from a short-term bed rest study

The absence of mechanical loading leads to a prompt increase in bone resorption measured by bone resorption markers. There is high potential that vibration training can positively influence bone metabolism in immobilized subjects, reduce the increase in osteoclastic activity and increase bone formation processes. We investigated whether vibration training at 20 Hz with an amplitude of 2–4 mm influences bone metabolism during immobilization. Eight male subjects (26.4 ± 4.9 years; 78.1 ± 9.5 kg) performed a 14 day bed rest in 6°-head down tilt (HDT). Subjects received vibration training for 2 × 5 min/day or a control intervention without vibration (crossover design). Calcium excretion and bone resorption markers C-telopeptide (CTX) and N-telopeptide (NTX) were analyzed from 24 h urine samples. Bone formation markers, bone alkaline phosphatase (bAP) and procollagen-N propeptide (PINP) were analyzed from fasting blood samples. Our results show an increase in bone resorption very early during HDT bed rest in both interventions (CTX: p < 0.01; NTX: p < 0.001). Vibration training did not have any different effect on bone resorption markers (CTX: p = 0.10; NTX: p = 0.58), bone formation markers (PINP: p = 0.21; bAP: p = 0.12) and calcium excretion (p < 0.64) compared to the control condition. Mere vibration training with 20 Hz for 2 × 5 min/day does not prevent increase in bone resorption as measured with the described methods in our short-term HDT bed rest.     

Relationships between muscle strength and muscle cross-sectional area in male sprinters and endurance runners

Summary The relationship between the cross-sectional area (CSA) and maximum voluntary isometric strength of the knee extensor muscles was measured in a group of untrained subjects (control group, n=30), a group of successful marathon runners (n=6) and a group of successful sprinters (n=6). All subjects were male, aged between 20 and 41 years. In the control group muscle strength was found to be positively correlated with lean body mass (p<0.01) and with muscle CSA as determined by computed tomography scanning of the leg at mid-thigh level (p<0.001). However, in spite of these significant relationships, there was considerable variability between subjects. The sprinters were significantly stronger than the endurance runners (p<0.01), but neither of the athletic groups differed significantly from the control group. Muscle CSA was greater in the sprinters than in the marathon runners but this difference was not significant. The ratio of muscle strength to CSA in the control group varied from 7.07 to 13.57. All the trained subjects fell within this normal range, but the sprinters' muscles were stronger per unit CSA than the muscles of the marathon runners (p<0.05). Since it is well established that the leg muscles of sprinters contain a high proportion of fast twitch (FT) muscle fibres whereas endurance runners have a high proportion of slow twitch (ST) fibres, these results suggest that the strength which can be produced by a muscle may depend on its fibre composition. Variation in the distribution of the different fibre types in the untrained population may therefore account at least in part for the wide variability observed in this group.Supported by a grant from Lipha Pharmaceuticals Ltd     

Association of single nucleotide polymorphisms in TPM1 rs11071720, rs3803499, rs12148828, and rs1972041 with the risk of nonsyndromic cleft lip with or without cleft palate in a sample of the Iranian population,a preliminary report

Several lines of evidence support an association between tropomyosin 1 (TPM1) and the risk of nonsyndromic cleft lip with or without cleft palate (NSCL/P). The present study aimed to investigate the association between TPM1 polymorphisms and the risk of NSCL/P in an Iranian population. This case‐control was done on 105 NSCL/P patients and 110 unrelated healthy controls. TPM1 rs11071720, rs3803499, rs12148828, and rs1972041 polymorphisms were genotyped by the polymerase chain reaction‐restriction fragment length polymorphism method. The finding showed that rs11071720 polymorphism significantly increased the risk of NSCL/P in homozygous codominant (odds ratio [OR] = 2.54, 95% confidence interval [CI] = 1.14–5.69, p = 0.023, TT vs. CC), recessive (OR = 2.33, 95% CI = 1.06–5.18, p = 0.021, TT vs. CT + CC), and allele (OR = 1.53, 95% CI = 1.02–2.30, p = 0.030, T vs. C). The rs12148828 polymorphism was associated with protection against NSCL/P in codominant (OR = 0.27, 95% CI = 0.15–0.48, p < 0.001, TC vs. TT) and allele (OR = 0.38, 95% CI = 0.22–0.64, p < 0.001, C vs. T). Regarding rs3803499, the findings proposed that this polymorphism significantly increased the risk of NSCL/P in codominant (OR = 3.86, 95% CI = 1.19–12.56, p = 0.025, CC vs. TT) and recessive (OR = 3.74, 95% CI = 1.09–14.15, p = 0.018, CC vs. CT + TT). No significant association was practical between rs1972041 polymorphism and NSCL/P. In conclusion, the findings proposed that TPM1 polymorphisms may contribute to the etiology of NSCL/P in a sample of the Iranian population.     

Skeletal muscle monocarboxylate transporter content is not different between black and white runners

The superior performance of black African runners has been associated with lower plasma lactate concentrations at sub-maximal intensities compared to white runners. The aim was to investigate the monocarboxylate transporters 1 (MCT1) and MCT4 content in skeletal muscle of black and white runners. Although black runners exhibited lower plasma lactate concentrations after maximum exercise (8.8 ± 2.0 vs. 12.3 ± 2.7 mmol l⁻¹, P < 0.05) and a tendency to be lower at 16 km h⁻¹ (2.4 ± 0.7 vs. 3.8 ± 2.4 mmol l⁻¹, P = 0.07) than the white runners, there were no differences in MCT1 or MCT4 levels between the two groups. For black and white runners together, MCT4 content correlated significantly with 10 km personal best time (r = −0.74, P < 0.01) and peak treadmill speed (r = 0.88, P < 0.001), but MCT1 content did not. Although whole homogenate MCT content was not different between the groups, more research is required to explain the lower plasma lactate concentrations in black runners.     

Relative importance of lean and fat mass on bone mineral density in a group of adolescent girls and boys

The aim of this study was to determine the relative importance of lean mass (LM) and fat mass (FM) on bone mineral density (BMD) in a group of adolescent girls and boys. A total of 65 adolescent boys and 35 adolescent girls participated in this study. Whole body (WB) and lumbar spine (L1–L4) BMD were measured by dual-energy X-ray absorptiometry (DXA). Body composition was assessed using the same technique. In boys, LM was strongly related to WBBMD (r = 0.68; p < 0.001) and to L1–L4 BMD (r = 0.61; p < 0.001), whereas FM was not positively related to BMD and was negatively associated with WB bone mineral apparent density (WBBMAD). In girls, both LM and FM were positively related to WBBMD (r = 0.41; p < 0.05 and r = 0.49; p < 0.01, respectively), whereas only FM was correlated to L1–L4 BMD (r = 0.33; p < 0.05). Finally, in a multiple regression analysis, FM was found to be a better positive determinant of WBBMD than LM in girls, whereas in boys, FM was found to be a negative determinant of WBBMD and L1–L4 BMD. This study suggests that LM is a strong determinant of WBBMD and L1–L4 BMD in boys, and that FM is a stronger determinant of WBBMD than LM in girls.     

Skeletal muscle telomere length in healthy, experienced, endurance runners

Measuring the DNA telomere length of skeletal muscle in experienced endurance runners may contribute to our understanding of the effects of chronic exposure to endurance exercise on skeletal muscle. This study compared the minimum terminal restriction fragment (TRF) length in the vastus lateralis muscle of 18 experienced endurance runners (mean age: 42 ± 7 years) to those of 19 sedentary individuals (mean age: 39 ± 10 years). The runners had covered almost 50,000 km in training and racing over 15 years. Minimum TRF lengths measured in the muscle of both groups were similar (P = 0.805) and within the normal range. Minimum TRF length in the runners, however, was inversely related to their years spent running (r = −0.63, P = 0.007) and hours spent training (r = −0.52, P = 0.035). Therefore, since exposure to endurance running may influence minimum TRF length, and by implication, the proliferative potential of the satellite cells, chronic endurance running may be seen as a stressor to skeletal muscle.