Trunk, Pelvis, Hip, and Knee Kinematics, Hip Strength, and Gluteal Muscle Activation During a Single-Leg Squat in Males and Females With and Without Patellofemoral Pain Syndrome

STUDY DESIGN: Controlled laboratory study using a cross-sectional design. OBJECTIVES: To determine whether there are any differences between the sexes in trunk, pelvis, hip, and knee kinematics, hip strength, and gluteal muscle activation during the performance of a single-leg squat in individuals with patellofemoral pain syndrome (PFPS) and control participants. BACKGROUND: Though there is a greater incidence of PFPS in females, PFPS is also quite common in males. Trunk kinematics may affect hip and knee function; however, there is a lack of studies of the influence of the trunk in individuals with PFPS. METHODS: Eighty subjects were distributed into 4 groups: females with PFPS, female controls, males with PFPS, and male controls. Trunk, pelvis, hip, and knee kinematics and gluteal muscle activation were evaluated during a single-leg squat. Hip abduction and external rotation eccentric strength was measured on an isokinetic dynamometer. Group differences were assessed using a 2-way multivariate analysis of variance (sex by PFPS status). RESULTS: Compared to controls, subjects with PFPS had greater ipsilateral trunk lean (mean +/- SD, 9.3 degrees +/- 5.30 degrees versus 6.7 degrees +/- 3.0 degrees; P = .012), contralateral pelvic drop (10.3 degrees +/- 4.7 degrees versus 7.4 degrees 3.8 degrees; P = .003), hip adduction (14.8 degrees +/- 7.8 degrees versus 10.8 degrees +/- 5.6 degrees; P<.0001), and knee abduction (9.2 degrees +/- 5.0 degrees versus 5.8 degrees +/- 3.4 degrees; P<.0001) when performing a single-leg squat. Subjects with PFPS also had 18% less hip abduction and 17% less hip external rotation strength. Compared to female controls, females with PFPS had more hip internal rotation (P<.05) and less muscle activation of the gluteus medius (P = .017) during the single-leg squat. CONCLUSION: Despite many similarities in findings for males and females with PFPS, there may be specific sex differences that warrant consideration in future studies and when clinically evaluating and treating females with PFPS. J Orthop Sports Phys Ther 2012;42(6):491-501, Epub 8 March 2012. doi:10.2519/jospt.2012.3987

Study of postures in sugarcane cutters in the Pontal of Paranapanema-SP, Brazil

The expansion of sugarcane monoculture in Brazil in the last decades has pointed out to the necessity of considering the question of sugarcane cutters occupational health. In this work we present a cross-sectional study aiming to examine the occupational posture of a group of sugarcane cutters, which work in a cane field located in the region of Pontal do Paranapanema-SP, Brazil. The study was made using the Ergonomic Analysis of Work - EAW methodology and the postural analysis method by Win-OWAS. Through the obtained records of postures, it was observed that during a workday the sugarcane cutters remain standing erect on two legs or in one leg 66% of the time and that their trunk remain tilted and in rotation, according to 63% of the positions categorized. It was also observed that the sugarcane cutter trunk performs repetitive and boundless movements during his routine of work, which can expose this individual to additional wear of their musculoskeletal functions. The activities in which the individual engages have favorable or adverse influence on his posture. The repetitive movements involved in specialized occupations are equivalent to repeated exercises, thus may be responsible for the excessive development of certain muscle groups. The study suggests that the postures adopted by sugarcane cutters can overload their musculoskeletal system and predispose the cutters to work-related musculoskeletal diseases.

Spinal cord injury as a trigger to develop periodic leg movements during sleep: an evolutionary perspective

The primary trigger to periodic limb movement (PLM) during sleep is still unknown. Its association with the restless legs syndrome (RLS) is established in humans and was reported in spinal cord injury (SCI) patients classified by the American Spinal Injury Association (ASIA) as A. Its pathogenesis has not been completely unraveled, though recent advances might enhance our knowledge about those malfunctions. PLM association with central pattern generator (CPG) is one of the possible pathologic mechanisms involved. This article reviewed the advances in PLM and RLS genetics, the evolution of CPG functioning, and the neurotransmitters involved in CPG, PLM and RLS. We have proposed that SCI might be a trigger to develop PLM.

Effects of ATP-induced leg vasodilation on VO2 peak and leg O2 extraction during maximal exercise in humans

[EN] During maximal whole body exercise VO2 peak is limited by O2 delivery. In turn, it is though that blood flow at near-maximal exercise must be restrained by the sympathetic nervous system to maintain mean arterial pressure. To determine whether enhancing vasodilation across the leg results in higher O2 delivery and leg VO2 during near-maximal and maximal exercise in humans, seven men performed two maximal incremental exercise tests on the cycle ergometer. In random order, one test was performed with and one without (control exercise) infusion of ATP (8 mg in 1 ml of isotonic saline solution) into the right femoral artery at a rate of 80 microg.kg body mass-1.min-1. During near-maximal exercise (92% of VO2 peak), the infusion of ATP increased leg vascular conductance (+43%, P<0.05), leg blood flow (+20%, 1.7 l/min, P<0.05), and leg O2 delivery (+20%, 0.3 l/min, P<0.05). No effects were observed on leg or systemic VO2. Leg O2 fractional extraction was decreased from 85+/-3 (control) to 78+/-4% (ATP) in the infused leg (P<0.05), while it remained unchanged in the left leg (84+/-2 and 83+/-2%; control and ATP; n=3). ATP infusion at maximal exercise increased leg vascular conductance by 17% (P<0.05), while leg blood flow tended to be elevated by 0.8 l/min (P=0.08). However, neither systemic nor leg peak VO2 values where enhanced due to a reduction of O2 extraction from 84+/-4 to 76+/-4%, in the control and ATP conditions, respectively (P<0.05). In summary, the VO2 of the skeletal muscles of the lower extremities is not enhanced by limb vasodilation at near-maximal or maximal exercise in humans. The fact that ATP infusion resulted in a reduction of O2 extraction across the exercising leg suggests a vasodilating effect of ATP on less-active muscle fibers and other noncontracting tissues and that under normal conditions these regions are under high vasoconstrictor influence to ensure the most efficient flow distribution of the available cardiac output to the most active muscle fibers of the exercising limb.

Cardiac output and leg and arm blood flow during incremental exercise to exhaustion on the cycle ergometer

[EN] To determine central and peripheral hemodynamic responses to upright leg cycling exercise, nine physically active men underwent measurements of arterial blood pressure and gases, as well as femoral and subclavian vein blood flows and gases during incremental exercise to exhaustion (Wmax). Cardiac output (CO) and leg blood flow (BF) increased in parallel with exercise intensity. In contrast, arm BF remained at 0.8 l/min during submaximal exercise, increasing to 1.2 +/- 0.2 l/min at maximal exercise (P < 0.05) when arm O(2) extraction reached 73 +/- 3%. The leg received a greater percentage of the CO with exercise intensity, reaching a value close to 70% at 64% of Wmax, which was maintained until exhaustion. The percentage of CO perfusing the trunk decreased with exercise intensity to 21% at Wmax, i.e., to approximately 5.5 l/min. For a given local Vo(2), leg vascular conductance (VC) was five- to sixfold higher than arm VC, despite marked hemoglobin deoxygenation in the subclavian vein. At peak exercise, arm VC was not significantly different than at rest. Leg Vo(2) represented approximately 84% of the whole body Vo(2) at intensities ranging from 38 to 100% of Wmax. Arm Vo(2) contributed between 7 and 10% to the whole body Vo(2). From 20 to 100% of Wmax, the trunk Vo(2) (including the gluteus muscles) represented between 14 and 15% of the whole body Vo(2). In summary, vasoconstrictor signals efficiently oppose the vasodilatory metabolites in the arms, suggesting that during whole body exercise in the upright position blood flow is differentially regulated in the upper and lower extremities.

Leg and arm lactate and substrate kinetics during exercise

[EN] To study the role of muscle mass and muscle activity on lactate and energy kinetics during exercise, whole body and limb lactate, glucose, and fatty acid fluxes were determined in six elite cross-country skiers during roller-skiing for 40 min with the diagonal stride (Continuous Arm + Leg) followed by 10 min of double poling and diagonal stride at 72-76% maximal O(2) uptake. A high lactate appearance rate (R(a), 184 +/- 17 micromol x kg(-1) x min(-1)) but a low arterial lactate concentration ( approximately 2.5 mmol/l) were observed during Continuous Arm + Leg despite a substantial net lactate release by the arm of approximately 2.1 mmol/min, which was balanced by a similar net lactate uptake by the leg. Whole body and limb lactate oxidation during Continuous Arm + Leg was approximately 45% at rest and approximately 95% of disappearance rate and limb lactate uptake, respectively. Limb lactate kinetics changed multiple times when exercise mode was changed. Whole body glucose and glycerol turnover was unchanged during the different skiing modes; however, limb net glucose uptake changed severalfold. In conclusion, the arterial lactate concentration can be maintained at a relatively low level despite high lactate R(a) during exercise with a large muscle mass because of the large capacity of active skeletal muscle to take up lactate, which is tightly correlated with lactate delivery. The limb lactate uptake during exercise is oxidized at rates far above resting oxygen consumption, implying that lactate uptake and subsequent oxidation are also dependent on an elevated metabolic rate. The relative contribution of whole body and limb lactate oxidation is between 20 and 30% of total carbohydrate oxidation at rest and during exercise under the various conditions. Skeletal muscle can change its limb net glucose uptake severalfold within minutes, causing a redistribution of the available glucose because whole body glucose turnover was unchanged.

Arterial O2 content and tension in regulation of cardiac output and leg blood flow during exercise in humans

[EN] A universal O2 sensor presumes that compensation for impaired O2 delivery is triggered by low O2 tension, but in humans, comparisons of compensatory responses to altered arterial O2 content (CaO2) or tension (PaO2) have not been reported. To directly compare cardiac output (QTOT) and leg blood flow (LBF) responses to a range of CaO2 and PaO2, seven healthy young men were studied during two-legged knee extension exercise with control hemoglobin concentration ([Hb] = 144.4 +/- 4 g/l) and at least 1 wk later after isovolemic hemodilution ([Hb] = 115 +/- 2 g/l). On each study day, subjects exercised twice at 30 W and on to voluntary exhaustion with an FIO2 of 0.21 or 0.11. The interventions resulted in two conditions with matched CaO2 but markedly different PaO2 (hypoxia and anemia) and two conditions with matched PaO2 and different CaO2 (hypoxia and anemia + hypoxia). PaO2 varied from 46 +/- 3 Torr in hypoxia to 95 +/- 3 Torr (range 37 to >100) in anemia (P < 0.001), yet LBF at exercise was nearly identical. However, as CaO2 dropped from 190 +/- 5 ml/l in control to 132 +/- 2 ml/l in anemia + hypoxia (P < 0.001), QTOT and LBF at 30 W rose to 12.8 +/- 0.8 and 7.2 +/- 0.3 l/min, respectively, values 23 and 47% above control (P < 0.01). Thus regulation of QTOT, LBF, and arterial O2 delivery to contracting intact human skeletal muscle is dependent for signaling primarily on CaO2, not PaO2. This finding suggests that factors related to CaO2 or [Hb] may play an important role in the regulation of blood flow during exercise in humans.

Carga óptima para el desarrollo de la potencia máxima en jóvenes tenistas durante ejercicios de media sentadilla y press banca

Programa de doctorado: Ciencias de la actividad física, salud y rendimiento deportivo

Assessing periodicity of periodic leg movements during sleep

Periodic leg movements (PLM) during sleep consist of involuntary periodic movements of the lower extremities. The debated functional relevance of PLM during sleep is based on correlation of clinical parameters with the PLM index (PLMI). However, periodicity in movements may not be reflected best by the PLMI. Here, an approach novel to the field of sleep research is used to reveal intrinsic periodicity in inter movement intervals (IMI) in patients with PLM.

Reproducibility and day time bias correction of optoelectronic leg volumetry: a prospective cohort study

Background Leg edema is a common manifestation of various underlying pathologies. Reliable measurement tools are required to quantify edema and monitor therapeutic interventions. Aim of the present work was to investigate the reproducibility of optoelectronic leg volumetry over 3 weeks' time period and to eliminate daytime related within-individual variability. Methods Optoelectronic leg volumetry was performed in 63 hairdressers (mean age 45 ± 16 years, 85.7% female) in standing position twice within a minute for each leg and repeated after 3 weeks. Both lower leg (legBD) and whole limb (limbBF) volumetry were analysed. Reproducibility was expressed as analytical and within-individual coefficients of variance (CVA, CVW), and as intra-class correlation coefficients (ICC). Results A total of 492 leg volume measurements were analysed. Both legBD and limbBF volumetry were highly reproducible with CVA of 0.5% and 0.7%, respectively. Within-individual reproducibility of legBD and limbBF volumetry over a three weeks' period was high (CVW 1.3% for both; ICC 0.99 for both). At both visits, the second measurement revealed a significantly higher volume compared to the first measurement with a mean increase of 7.3 ml ± 14.1 (0.33% ± 0.58%) for legBD and 30.1 ml ± 48.5 ml (0.52% ± 0.79%) for limbBF volume. A significant linear correlation between absolute and relative leg volume differences and the difference of exact day time of measurement between the two study visits was found (P < .001). A therefore determined time-correction formula permitted further improvement of CVW. Conclusions Leg volume changes can be reliably assessed by optoelectronic leg volumetry at a single time point and over a 3 weeks' time period. However, volumetry results are biased by orthostatic and daytime-related volume changes. The bias for day-time related volume changes can be minimized by a time-correction formula.