The energy cost of walking or running on sand

Summary Oxygen uptake ( O₂) at steady state, heart rate and perceived exertion were determined on nine subjects (six men and three women) while walking (3–7 km · h^–1) or running (7–14 km · h^–1) on sand or on a firm surface. The women performed the walking tests only. The energy cost of locomotion per unit of distance (C) was then calculated from the ratio of O₂ to speed and expressed in J · kg^–1 · m^–1 assuming an energy equivalent of 20.9 J · ml O₂ ^–1. At the highest speedsC was adjusted for the measured lactate contribution (which ranged from approximately 2% to approximately 11% of the total). It was found that, when walking on sand,C increased linearly with speed from 3.1 J · kg^–1 · m^–1 at 3 km · h^–1 to 5.5 J · kg^–1 · m^–1 at 7 km · h^–1, whereas on a firm surfaceC attained a minimum of 2.3 J · kg^–1 · m^–1 at 4.5 km · h^–1 being greater at lower or higher speeds. On average, when walking at speeds greater than 3 km · h^–1,C was about 1.8 times greater on sand than on compact terrain. When running on sandC was approximately independent of the speed, amounting to 5.3 J · kg^–1 · m^–1, i.e. about 1.2 times greater than on compact terrain. These findings could be attributed to a reduced recovery of potential and kinetic energy at each stride when walking on sand (approximately 45% to be compared to approximately 65% on a firm surface) and to a reduced recovery of elastic energy when running on sand.     

The Internet and health promotion: a content analysis of the official websites of Italian Public Health Authorities

The current spread of Internet has made possible unprecedented access to health information, with important potential consequences on the world of health. Through an analysis of the official websites of the Italian Local Health Authorities (LHAs), we aimed to evaluate their characteristics and their completeness. The sample frame comprised 177 official websites out of a total of 187 Italian LHAs working in the study period; they were analysed according to the content analysis method. Almost all LHAs have a working official website. Almost all the websites have pages dedicated to prevention services, while only six websites have a forum. Health promotion content is more often present, more accessible and more extensive in Northern Italy. The analysis of the Italian case shows that LHA websites provide “cold” information, not making the most of interactive online instruments. Considering the important role played by these organisations at the national level, more effort is needed to fulfil their role of health communication providers.     

Torque and surface mechanomyogram parallel reduction during fatiguing stimulation in human muscles

The purpose of the study was to verify, by means of torque and mechanomyogram (MMG) compared analysis, the validity of MMG as a tool to investigate the contractile changes due to localized muscular fatigue induced by stimulation protocols usually employed for sport training and rehabilitation programs. Ten healthy sedentary subjects participated in the study. Torque produced by the dominant biceps brachii (BB) and vastus lateralis (VL) during transcutaneous stimulated contractions has been recorded by a load cell strapped to the subjects’ wrist and distal one-third of the tibia, respectively. MMG was detected over the muscle bellies during a monopolar supramaximal stimulation of the main motor point. After potentiation, the fatiguing stimulation was administered. It consisted of 50 cycles, with 2 s of 50 Hz and 25 s of 2 Hz. Averaged normalized values of peak torque (pT) and MMG peak-to-peak (MMG-pp) of the subjects group decreased from their initial 100% values to 55% (pT) and 60% (MMG-pp) for BB and to 43% (pT) and 47% (MMG-pp) for VL. The pT% and MMG-pp% changes throughout the stimulation protocol presented high correlation (BB: R=0.95, P<0.001; VL: R=0.94, P<0.001). This correlation suggests that MMG could be used to follow muscle mechanical fatigue development when torque output is not or hardly detectable such as during electrical stimulation programs employed for sport training or rehabilitation protocols.     

The influence of exercise intensity on the power spectrum of heart rate variability

Summary The power spectral analysis of R-R interval variability (RRV) has been estimated by means of an autoregressive method in seven sedentary males at rest, during steady-state cycle exercise at 21 percent maximal oxygen uptake. (% V _{O 2max}), SEM 2%, 49% V_{O 2max}, SEM 2% and 70% V_{O 2max}, SEM 2% and during recovery. The RRV, i.e. the absolute power of the spectrum, decreased 10, 100 and 500 times in the three exercise intensities, returning to resting value during recovery. In the RRV power spectrum three components have been identified: (1) high frequency peak (HF), central frequency about 0.24 Hz at rest and recovery, and 0.28 Hz, SEM 0.02, 0.37 Hz, SEM 0.03 and 0.48 Hz, SEM 0.06 during the three exercise intensities, respectively; (2) low frequency peak (LF), central frequency about 0.1 Hz independent of the metabolic state; (3) very low frequency component (VLF), <0.05 Hz, no peak observed. The HF peak power, as a percentage of the total power (HF%), averaged 16%, SEM 5% at rest and did not change during exercise, whereas during recovery it decreased to 5%–10%. The LF% and VLF% were about 50% and 35% at rest and during low exercise intensity, respectively. At higher intensities, LF% decreased to 16% and VLF% increased to 70%. During recovery a return to resting values occurred. The HF component may reflect the increased respiratory rate and the LF peak changes the resetting of the baroreceptor reflex with exercise. The hypothesis is made that VLF fluctuations in heart rate might be partially mediated by the sympathetic system.     

Bladder cancer, GSTs, NAT1, NAT2, SULT1A1, XRCC1, XRCC3, XPD genetic polymorphisms and coffee consumption: a case–control study

The aim of the study was to investigate NAT1, NAT2, GSTM1, GSTT1, GSTP1, SULT1A1, XRCC1, XRCC3 and XPD genetic polymorphisms, coffee consumption and risk of bladder cancer (BC) through a hospital-based case–control study. The study population included 197 incident BC cases and 211 controls. The association between genetic polymorphisms, coffee drinking and BC risk was assessed by logistic regression taking into account age, education, tobacco smoking and occupational exposures to polycyclic aromatic hydrocarbons and aromatic amines. No association was found between the genetic polymorphisms investigated and BC risk according to coffee consumption apart of a significant increased BC risk among GSTP1 105-114 Val carriers heavy coffee drinkers (>3 cups/day) (OR 3.18, 95%CI 1.06–9.55). In conclusion our findings suggest a very limited role, if any, of genetic polymorphisms investigated in modulating the BC risk in coffee drinkers.     

Time color map and histogram of electromyography (EMG) sample amplitudes: possible tools for global electromyogram analysis by images

Purpose

To present a method for surface electromyogram (EMG) analysis by images.

Methods

12 healthy sedentary males were studied. Surface EMG (from lateral deltoid) was recorded (1000 samples/s) and analysed during self-selected angular speed shoulder abduction/adduction actions, made at 40% of 1 revolution maximum, up to exhaustion. EMG was rectified and normalized to its maximum (100%). Histogram of sample amplitudes: the 0–100% amplitude range was divided in 20 levels (step 5%). Each sample was assigned to its bin for the histogram generation 2D time color map: the amplitude range was divided in five colored levels: blue (0–20%), green (21–40%), yellow (41–60%), orange (61–80%), red (81–100%). Along the time bar each ms was colored according to the sample relative amplitude. The whole colored bar was divided into 100 ms slices. These short color bars were graphically stacked one on top of each other and interpolated on the x/y plane using a standard contour plotting procedure. The spike shape analysis (SSA) was performed and the average rectified value (ARV) was calculated.

Results

From the first to the last action the histogram median amplitude increased from 34.33 ± 12.36 to 46.74 ± 14.04%. On the 2D map the areas of activity hues enlarged in both directions showing more regular recurrence of longer electrical events. As expected, the ARV increased and the SSA reflected the spikes changes at fatigue.

Conclusions

Histogram of the EMG sample amplitudes and 2D time color map provide data, at a glance, about the regularity of the EMG spikes occurrence and their amplitude distribution. This is a different, adjunct information with respect to the one provided by traditional EMG time domain analysis measurements.

     

Marketing and pricing strategies of online pharmacies

Internet and e-commerce have profoundly changed society, the economy, and the world of health care. The web offers opportunities to improve health, but it may also represent a big health hazard since it is a basically unregulated market with very low consumer protection. In this paper we analyze marketing and pricing strategies of online pharmacies (OPs). Our analysis shows that OPs use strategies that would be more suitable for a commodity market than for drugs. These strategies differentiate according to variety (brand or generic), quality, quantity, and target group. OPs are well aware that the vacuum in the legislation allows them to reach a target of consumers that pharmacies cannot normally reach, such as those who would like to use the drug without consulting a physician (or, even worse, against the physician's advice). In this case, they usually charge a higher price, reassure the users by minimizing on the side effects, and induce them to bulk purchase through sensible price discounts.This analysis suggests that the selling of drugs via the Internet can turn into a “public health risk”, as has been pointed out by the US Food and Drug Administration.     

Muscular sound and force relationship during isometric contraction in man

Summary The contracting muscle generates a low frequency sound detectable at the belly surface, ranging from 11 to 40 Hz. To study the relationship between the muscular sound and the intensity of the contraction a sound myogram (SMG) was recorded by a contact sensor from the biceps brachii of seven young healthy males performing 4-s isometric contractions from 10% to 100% of the maximal voluntary contraction (MVC), in 10% steps. Simultaneously, the electromyogram (EMG) was recorded as an index of muscle activity. SMG and EMG were integrated by conventional methods (iSMG and iEMG). The relationship between iSMG and iEMG vs MVC% is described by parabolic functions up to 80% and 100% MVC respectively. Beyond 80% MVC the iSMG decreases, being about half of its maximal value at 100% MVC. Our results indicate that the motor unit recruitment and firing rate affect the iSMG and iEMG in the same way up to 80% MVC. From 80% to 100% MVC the high motor units' discharge rate and the muscular stiffness together limit the pressure waves generated by the dimensional changes of the active fibres. The muscular sound seems to reflect the intramuscular visco-elastic characteristics and the motor unit activation pattern of a contracting muscle.     

Effect of accelerometer location on mechanomyogram variables during voluntary,constant-force contractions in three human muscles

To understand better the features of the mechanomyogram (MMG) with different force levels and muscle architectures, the MMG signals detected at many points along three muscles were analysed by the application of a linear array of MMG sensors (up to eight) over the skin. MMG signals were recorded from the biceps brachii, tibialis anterior and upper trapezius muscles of the dominant side of ten healthy male subjects. The accelerometers were aligned along the direction of the muscle fibres. One accelerometer was located over the distal muscle innervation zone, and the other six or seven accelerometers were placed over the muscle, forming an array of sensors with fixed distances between them. The array covered almost the entire muscle length in all cases. MMG signals detected from adjacent accelerometers had similar shapes, with correlation coefficients ranging from about 0.5 to about 0.9. MMG amplitude and characteristic spectral frequencies significantly depended on accelerometer location. The MMG amplitude was maximum at the muscle belly for the biceps brachii and the tibialis anterior. Higher MMG characteristic spectral frequencies were associated with higher amplitudes in the case of the biceps brachii, whereas the opposite was observed for the tibialis anterior muscle. In the upper trapezius, the relationship between characteristic spectral frequencies, MMG amplitude and contraction force depended on the accelerometer location. This suggested that MMG spectral features do not only reflect the mechanical properties of the recruited muscle fibres but depend on muscle architecture and motor unit territorial distribution. It was concluded that the location of the accelerometer can have an influence on both amplitude and spectral MMG features, and this dependence should be considered when MMG signals are used for muscle assessment.