Biomechanics of sprint running. A review.

Understanding of biomechanical factors in sprint running is useful because of their critical value to performance. Some variables measured in distance running are also important in sprint running. Significant factors include: reaction time, technique, electromyographic (EMG) activity, force production, neural factors and muscle structure. Although various methodologies have been used, results are clear and conclusions can be made. The reaction time of good athletes is short, but it does not correlate with performance levels. Sprint technique has been well analysed during acceleration, constant velocity and deceleration of the velocity curve. At the beginning of the sprint run, it is important to produce great force/power and generate high velocity in the block and acceleration phases. During the constant-speed phase, the events immediately before and during the braking phase are important in increasing explosive force/power and efficiency of movement in the propulsion phase. There are no research results available regarding force production in the sprint-deceleration phase. The EMG activity pattern of the main sprint muscles is described in the literature, but there is a need for research with highly skilled sprinters to better understand the simultaneous operation of many muscles. Skeletal muscle fibre characteristics are related to the selection of talent and the training-induced effects in sprint running. Efficient sprint running requires an optimal combination between the examined biomechanical variables and external factors such as footwear, ground and air resistance. Further research work is needed especially in the area of nervous system, muscles and force and power production during sprint running. Combining these with the measurements of sprinting economy and efficiency more knowledge can be achieved in the near future.     

Force-, EMG-, and elasticity-velocity relationships at submaximal,maximal and supramaximal running speeds in sprinters

Summary The relationships between ground reaction forces, electromyographic activity (EMG), elasticity and running velocity were investigated at five speeds from submaximal to supramaximal levels in 11 male and 8 female sprinters. Supramaximal running was performed by a towing system. Reaction forces were measured on a force platform. EMGs were recorded telemetrically with surface electrodes from the vastus lateralis and gastrocnemius muscles, and elasticity of the contact leg was evaluated with spring constant values measured by film analysis. Data showed increases in most of the parameters studied with increasing running speed. At supramaximal velocity (10.36±0.31 m×s⁻¹; 108.4±3.8%) the relative increase in running velocity correlated significantly (P<0.01) with the relative increase in stride rate of all subjects. In male subjects the relative change in stride rate correlated with the relative change of IEMG in the eccentric phase (P<0.05) between maximal and supramaximal runs. Running with the towing system caused a decrease in elasticity during the impact phase but this was significant (P<0.05) only in the female sprinters. The average net resultant force in the eccentric and concentric phases correlated significantly (P<0.05−0.001) with running velocity and stride length in the maximal run. It is concluded that (1) increased neural activation in supramaximal effort positively affects stride rate and that (2) average net resultant force as a specific force indicator is primarily related to stride length and that (3) the values in this indicator may explain the difference in running velocity between men and women.     

Pancreatic acinar ultrastructure in human acute pancreatitis

Summary Ultrastructural alterations in pancreatic acini from six patients operated for acute necrotizing pancreatitis are described. One of the patients suffered from biliary tract disease, the rest had excessive alcohol intake as the presumed aetiology. Areas of the pancreatic parenchyma showing oedematous inflammation in light microscopy were studied in the electron microscope. Findings in acinar cells included changes in zymogen granules and an increased autophagocytosis in addition to unspecific organelle alterations. Zymogen granules showed increase in size and number, loss or variation of electron-density and peripheral dissolution. Increased autophagic activity was indicated by several autophagic vacuoles and residual bodies. Acinar lumina were dilated showing effacement of microvilli and invaginations in the luminal plasma membrane of the acinar cells. In acinar lumina and in the interstitium fibrillar material was observed, with an increasing frequency in those areas showing severe cellular disintegration. These findings suggest: 1) an increased activity of zymogen granules, 2) an increased autophagocytosis, and 3) penetration of acinar luminal contents into the interstitium.     

Work stress,nonwork stress,and health

This paper examines the interface between work stress and nonwork stress and how it relates to health. Results indicate that the way people feel at work is largely a function of conditions at work. Similarly, the way people feel outside of work is largely a function of things that occur outside the job. Both work and nonwork stress are independently associated with physical and mental health, although the relationship between nonwork stress and health is slightly stronger. Excessive demands or stresses in one domain can interfere with life in the other. Such conflict operates equally in both directions. When present it can be an added source of stress and adversely affect health. Taken together these findings suggest that the stress people experience at work is not simply a reflection of their "personal problems." This has implications for the design of health promotion and stress prevention programs in the workplace.     

Phase I trial of systemic oxaliplatin combination chemotherapy with hepatic arterial infusion in patients with unresectable liver metastases from colorectal cancer.

PURPOSE: To determine the maximum-tolerated dose (MTD) of concurrent systemic oxaliplatin (Oxal) combinations plus hepatic arterial infusion (HAI) in patients with unresectable hepatic metastases from colorectal cancer. PATIENTS AND METHODS: Thirty-six patients (89% previously treated) with unresectable liver metastases were treated with concurrent HAI and systemic Oxal plus irinotecan (CPT-11; group A) or Oxal, fluorouracil (FU), and leucovorin (LV; group B). Systemic chemotherapy was administered every 2 weeks concurrent with 2 weeks of HAI floxuridine (FUDR) and dexamethasone (Dex) every 28 days. RESULTS: The MTD for patients in group A was Oxal 100 mg/m(2), CPT-11 150 mg/m(2), and FUDR 0.12 mg/kg x 30 mL divided by pump flow rate. The MTD for group B was Oxal 100 mg/m(2), LV 400 mg/m(2), and FU 1,400 mg/m(2) by continuous infusion over 48 hours, with the same FUDR dose as in group A. Grade 3 or 4 toxicities in groups A and B included diarrhea (24% and 20%), neutropenia (10% and 7%), neurotoxicity (24% and 20%), and bilirubin more than 3 mg/mL (5% and 7%, respectively). The complete and partial response rate totaled 90% for group A and 87% for group B. Median survival time was 36 and 22 months for groups A and B, respectively. Seven patients in group A were ultimately able to undergo liver resection. CONCLUSION: Combination therapy with HAI FUDR and Dex plus systemic Oxal combinations may be safely administered to patients with colorectal cancer. The high response rate (88%) and the possibility of conversion to resectability, despite disease progression on prior systemic regimens, suggest that these combinations should be evaluated in larger studies as first- or second-line therapy in patients with hepatic metastases from colorectal cancer.     

Anomalous boron isotope effects on electronic structure and lattice dynamics of CuB2O4

Copper metaborate had a unique crystal structure and exhibited noteworthy magnetic phase transitions at 21 and 10 K. The electronic structure and lattice dynamics of copper metaborate Cu¹¹B₂O₄ single crystals were investigated and compared with the optical properties of CuB₂O₄, to assess the boron isotope effect. The optical absorption spectrum at room temperature revealed two charge-transfer bands at approximately 4.30 and 5.21 eV with an extrapolated direct optical band gap of 3.16 ± 0.07 eV. Compared with the data on CuB₂O₄, the electronic transitions were shifted to lower energies upon the replacement of a heavier boron isotope. The band gap was also determined to be lower in Cu¹¹B₂O₄. Anomalies in the temperature dependence of the optical band gap were observed below 21 K. Furthermore, 38 Raman-active phonon modes were identified in the room-temperature Raman scattering spectrum of Cu¹¹B₂O₄, which were also observed in CuB₂O₄ with a shift to lower frequencies. No broadening caused by isotopic changes was observed. As the temperature decreased, phonon frequencies shifted to higher wavenumbers and the linewidth decreased. Anomalous softening in the Raman peaks below 21 K was also revealed.

Copper metaborate had a unique crystal structure and exhibited noteworthy magnetic phase transitions at 21 and 10 K.     

The Effect of High‐Mobility Group Box 1 in Rat Steatotic and Nonsteatotic Liver Transplantation From Donors After Brain Death

High‐mobility group box 1 (HMGB1) has been described in different inflammatory disorders, and the deleterious effects of brain death (BD) may counteract the protection conferred by ischemic preconditioning (IP), the only surgical strategy that is being applied in clinical liver transplantation. Our study examined how HMGB1 may affect preconditioned and unpreconditioned steatotic and nonsteatotic liver grafts from donors after BD (DBDs) for transplantation. HMGB1 was pharmacologically modulated in liver grafts from DBDs, and HMGB1‐underlying mechanisms were characterized. We found that BD decreased HMGB1 in preconditioned and unpreconditioned livers and was associated with inflammation and damage. Exogenous HMGB1 in DBDs activates phosphoinositide‐3‐kinase and Akt and reduces hepatic inflammation and damage, increasing the survival of recipients. Combination of IP and exogenous HMGB1 shows additional benefits compared with HMGB1 alone. This study provides new mechanistic insights into the pathophysiology of BD‐derived liver graft damage and contributes to the development of novel and efficient strategies to ultimately improve liver graft quality.     

Acute leukocyte,cytokine and adipocytokine responses to maximal and hypertrophic resistance exercise bouts

The purpose of this study was to examine the acute immune response (circulating levels of leukocytes, cytokines and adipocytokines) to maximal resistance (MAX, 15 × 1RM) and hypertrophic resistance (HYP, 5 × 10RM) exercise bouts. Twelve healthy men (age = 28.2 ± 3.5 years, weight = 78.6 ± 10.4 kg, height 178.8 ± 5.0 cm, fat percentage = 16.5 ± 3.5 %) participated in the study. Blood was sampled before, immediately after and 15 and 30 min after exercise. Leukocytes (WBC) significantly increased immediately after HYP (p < 0.01), whereas in MAX, increases in WBC became significant after 30 min (p < 0.05). Lymphocytes increased only after HYP (p < 0.001), while MAX induced lymphopenia during recovery (p < 0.01). Monocyte chemoattractant protein-1 (MCP-1) decreased (p < 0.05) and interleukin-1 receptor antagonist (IL-1ra) increased after HYP, which were not observed after MAX. Adipsin and resistin decreased after both exercise bouts (p < 0.05), which suggest that heavy resistance exercise is at least transiently beneficial for adipocytokine profile. Immediate mechanical stress seemed similar as no differences in myoglobin response were observed. The higher magnitude of metabolic demand reflected in higher lactate response in HYP could be the reason for the significantly high responses in WBC, IL-1ra and decrease in MCP-1.