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Background: Diabetes damages peripheral tissues; however, its effects on the lung are less known. Lung diffusing capacity (DLCO) is influenced by alveolar-capillary membrane conductance (DM) and pulmonary capillary blood volume (VC), both of which are reduced in adults with type 1 diabetes (T1D). Objective: We sought to determine if diabetes duration affects DLCO, DM, VC, and cardiac output (Q). Methods: 24 T1D patients (10.7-52.8 years) and 24 non-diabetic controls were recruited and had DLCO, DM, VC, and Q measured at rest and during exercise (40, 70 and 90% VO2max). Results: When stratified into two groups based on age (young, <20.6 years old), there were no significant differences in DLCO, DM, VC, or Q (all of which were normalized to body surface area [BSA]) in the young group or in the old group. When stratified by diabetes duration (short duration, 0.33-8.9 years vs. long duration, 9.6-28 years), the T1D patients in the long duration group had lower DLCO/BSA and DM/BSA compared to the controls (p < 0.05). There were no differences in any of the variables in the short duration group. Conclusions: This study has shown that duration of diabetes is associated with decrements in diffusing capacity and its components. © 2016 S. Karger AG, Basel [ABSTRACT FROM AUTHOR]

The article discusses research on the development of a user-friendly conversion table for determining lower body positive pressure (LBPP) treadmill speed required to match a non-LBPP treadmill metabolic output. Topics explored include the increasing use of LBPP treadmills that support body weight of users in a sports setting, the assessment of metabolic expenditure on an LBPP treadmill, and the statistical analyses of physiologic data gathered.

The article discusses research which investigated body weight support (BWS) accuracy of the AlterG Anti-Gravity treadmill. Topics explored include the experimental protocol observed such as machine calibration and predicted weight calculation, statistical analyses of predicted and measured mean weights gathered, and the factors that need to be considered by coaches before incorporating the AlterG treadmill in exercise programs.

People intuitively walk at a speed that minimizes energy cost per meter. Therefore, the selective advantages of energetic efficiency are thought to drive individuals' preferred walking speed (PWS). This presumption disregards fuel partitioning, which may, in fact, be significant due to the disparate sizes of the carbohydrate (CHO) and fat reservoirs, coupled with the necessity of CHO for high intensity exercise. Potentially, PWS may reflect CHO conservation more than energetic efficiency per se. This study was designed to determine if PWS over a variety of conditions conforms to the CHO sparing hypothesis. Six subjects walked on a treadmill at five speeds: their PWS and speeds 0.45 and 0.22 m/s below and above PWS, under loads of 0, 10, and 20% of body weight, as well as at grades of -6.25, 0 and +6.25%. Oxygen consumption, carbon dioxide production and respiratory exchange ratio were measured over each 10 min bout to calculate total energy, CHO and fat usage. The subjects' mean (±SD) unloaded, level PWS was 1.32 ± 0.11 m/s. PWS was reduced by the 20% load and uphill grade, but not affected by the 10% load or downhill grade. Carbohydrate provided ≥50% of required energy in all conditions. The CHO oxidation rate was related to speed such that the gain was greater at speeds above than below the PWS; however, differences in CHO oxidation between conditions did not correspond to differences in PWS. We conclude that CHO sparing is not the primary determinant of PWS during externally loaded or grade walking. [ABSTRACT FROM AUTHOR]

The article discusses findings of a study which determined whether pedaling strategy during a 30-minute simulated time trial affected caloric requirements. Due to the success of several cyclists including Lance Armstrong, riding at high cadences has become popular. A definition of optimal pedal rate is presented, referring to a trade-off between the added cost of unloaded pedaling as pedal rate increases and the decreases in peak force experienced by muscles that are distributing the workload.

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This study examined the effects of drafting in swimming on heart rate and blood lactate in collegiate swimmers. Subjects consisted of two groups, one male and one female. Subjects swam eight 400m swims with the swimmers in a straight line. They swam in each position in the line (1,2,3,4) during swims where the subjects were separated by five or ten seconds (5-sec draft, and 10-sec draft, respectively). Heart rates were measured immediately post exercise. Lactate levels were measured two min post-exercise. Heart rates were significantly higher in position one in both the 5-sec and 10-sec draft conditions (p=0.015), but were not different between positions two through four. Lactate levels were significantly higher in position one than in position three or four in both drafting conditions (p=0.001), but positions two through four were not different. Results indicate that whether a person is swimming in a 5-sec or 10-sec interval draft the leader of a multi-person draft appears to expend more energy based on heart rate and lactate data. It can be concluded that there is a drafting effect in swimming, but little apparent change in energy expenditure the further back in the draft the person is swimming. These results may have implications for training swimmers when pool conditions dictate that numerous people swim in the same lane. [ABSTRACT FROM AUTHOR]

A number of methods have been used to evaluate diaphragm or inspiratory muscle function and fatigue in humans. These range from simple measurement of maximal inspiratory pressure (MIP) to transdiaphragmatic pressures elicited by bilateral phrenic nerve stimulation (BPNS). The techniques vary in simplicity and in their level of discomfort for the subject or patient, but also may vary in the information they give, in that a technique such as BPNS removes the voluntary component from the pressure generation. The purpose of this study was to compare three methods of assessing inspiratory fatigue. Six subjects performed 16 minutes of resisted inspiration at approximately 30% of MIP. Maximal inspiratory pressure, BPNS at twitch, 10Hz and 20Hz, and maximal sniff pressure were measured before the bout and at 4, 8, 12 and 16 minutes. By 16 minutes, MIP and BPNS at all frequencies were decreased by approximately 5-25% compared to pre- and 4-min measurements. Further, they varied together, indicating that as voluntary-induced measurements decreased or increased, so did stimulated measurements. Sniff pressures did not change across times in this group of subjects. We conclude from this early data that MIP may be an adequate substitute for BPNS in assessing inspiratory fatigue. [ABSTRACT FROM AUTHOR]

Abdominal exercises, such as sit ups and leg lifts, are used to enhance strength of the core muscles. An overlooked aspect of abdominal exercises is the compression the abdomen, leading to increased diaphragmatic work. We hypothesized that core exercises would produce a variety of transdiaphragmatic pressures. We also sought to determine if some of the easy exercises would produce pressures sufficient for a training stimulus to the diaphragm. We evaluated the effect of 13 different abdominal exercises, ranging in difficulty, on transdiaphragmatic pressure (Pdi), an index of diaphragmatic activity. Six healthy subjects, aged 22 to 53, participated. Each subject was instrumented with two balloon-tipped catheters to obtain gastric and esophageal pressures, from which Pdi was calculated. Prior to initiating the exercises, each subject performed a maximal inspiratory pressure (MIP) maneuver. Resting Pdi was also measured. The exercises were performed from least to most difficult, with five repetitions each. There was a significant difference between the exercises and the MIP Pdi, as well as between the exercises and resting Pdi (p < 0.001). The exercises stratified into three Pdi levels. Seven of the exercises yielded Pdi =50% of the Pdi during the MIP maneuver, which may provide a training stimulus to the diaphragm if used as a regular exercise. The Pdi measurements also provide insight into diaphragm recruitment during different core exercises, and may aid in the design of exercises to improve diaphragm strength and endurance. [ABSTRACT FROM AUTHOR]

Lower body positive pressure (LBPP), or 'anti-gravity' treadmills ® have become increasingly popular among elite distance runners. However, to date, few studies have assessed the effect of body weight support (BWS) on the metabolic cost of running among elite runners. This study evaluated how BWS influenced the relationship between velocity and metabolic cost among 6 elite male distance runners. Participants ran three- 16 minute tests consisting of 4 stages of 4 minutes at 8, 7, 6 and 5 min⋅mile-1 pace (3.35, 3.84, 4.47 and 5.36 m⋅s-1), while maintaining an aerobic effort (Respiratory Exchange Ratio ≤1.00). One test was run on a regular treadmill, one on an anti-gravity treadmill with 40% BWS and one with 20% BWS being provided. Expired gas data were collected and regression equations used to determine and compare slopes. Significant decreases in oxygen uptake (...O2) were found with each increase in BWS (p < 0.001). At 20% BWS, the average decrease in net VO2 was greater than proportional (34%), while at 40% BWS, the average net reduction in VO2 was close to proportional (38%). Across velocities, the slope of the relationship between VO2 and velocity (...O2/Δv) was steeper with less support. The slopes at both the 20% and 40% BWS conditions were similar, especially when compared to the regular treadmill. Variability in VO2 between athletes was much greater on the LBPP treadmill and was greater with increased levels of BWS. In this study we evaluated the effect of body weight support on ...O2 among elite distance runners. We have shown that oxygen uptake decreased with support, but not in direct proportion to that support. Further, because of the high variability in oxygen uptake between athletes on the LBPP treadmill, prediction equations may not be reliable and other indicators (heart rate, perceived exertion or directly measured oxygen uptake) should be used to guide training intensity when training on the LBPP treadmill. [ABSTRACT FROM AUTHOR]

Restriction of expansion of the lungs or chest wall impedes inflation of the lungs during inhalation. Functional changes occurring during such restriction include reduced pulmonary and/or chest wall compliance, decreases in pulmonary function, and ultimately a decrease in exercise performance. Such restriction can be seen in several pathologic conditions such as scoliosis or obesity, as well as occupational situations such as the wearing of bullet-proof vests. This study investigated the hypothesis that tightened football shoulder pads produce decrements in pulmonary function similar to those shown in previous studies involving other external chest-wall restricting devices. In this study, 24 subjects, all members of a collegiate division IAA football team and used to wearing the pads, performed standard pulmonary function tests while wearing no pads (control, CTRL), wearing pads that were not secured (pads loose, PL) and while wearing pads secured "game-tight" (pads tight, PT). The data showed that both forced vital capacity (FVC) and forced expiratory volume in one second (FEV1.0) were significantly decreased in the PT condition compared to either the CTRL or PL condition, with no changes in the FEV1.0/FVC ratio or peak expiratory flow rate. These results are consistent with a restrictive condition and support our hypothesis that tightened shoulder pads reduce pulmonary function. Further studies remain to be performed to determine whether these changes lead to decreased exercise performance and whether equipment modifications can be made to limit alterations in pulmonary function without decreasing the protective value of the pads. Key PointsThe shoulder pads used in American football extend to the xyphoid process and may provide a restriction to breathing. This was tested in the present study in 24 college-level football players with normal resting pulmonary function.The results showed that there was a decrease in FVC of approximately 150 ml and a similar decrease in FEV1.0.Similar decreases in pulmonary function have been shown to provide a limitation to exercise capacity in otherwise healthy adults.Further study is needed to determine whether these changes lead to decrements in performance.

The purpose of this study was to evaluate contractile properties of the tibialis anterior of paralyzed and non-paralyzed subjects. The contractile properties and the fatigability of the tibialis anterior muscle (TA) were tested in 8 spinal cord injured (SCI) and 8 control individuals. The TA was stimulated at frequencies from 10 to 100 Hz to determine a force-frequency curve. A fatigue bout was also performed by stimulating the muscle at 40 Hz every two seconds for three minutes. The SCI muscles produced lower forces overall, but higher forces relative to maximal force at lower frequencies, shifting the force-frequency curve of the SCI group to the left. The half-relaxation time and rate of relaxation at 40 Hz was slower in the SCI muscles than in the control muscles (127 ± 18.4 ms vs. 78 ± 8.7 ms, 6 ± 1.5 kg·s(-1) 20 ± 4.1 kg·s(-1) respectively). In addition, force loss and slowing of relaxation during the fatigue protocol were not significantly different between the two groups due to high variability in the SCI group. The TA of the SCI group had slower contractile properties than the control group and fatigability was not significantly different between the SCI and control group. The protocol may be useful to assess training effects during rehabilitation of paralyzed muscle. Key PointsStimulated contractions were tested on controls and spinal cord injured subjects to determine differences in contractile characteristics of the tibialis anterior (ta) muscle.Forces were lower in the ta of the spinal cord injured subjects compared to the controls.All indices of contractile speed were slower in the spinal cord injured subjects than in the controls.The reason for possible differences in contractile capabilities and other biochemical indices of contractile speed in disused muscle need to be further evaluated.

The purpose of this study was to examine the effect of varying recovery intervals on multiple-bout, short-duration, high-intensity cycling efforts of adult men supplemented with creatine (Cr) or a placebo (Pl). Thirty subjects underwent 3 trials of a maximal cycling protocol (T(0), T(1), T(2)). T(0) included V(O)2 max testing and familiarization with the sprint cycling protocol. T(1) consisted of 8 15-second bouts of sprint cycling exercise. Subjects were randomly assigned to recovery interval groups (1 minute, 3 minutes, 6 minutes), and Cr or Pl groups (0.3 g x kg(-1) x d(-1)). Posttesting (T(2)) took place 7 days after T(1) and consisted of an identical protocol as during T(1). Changes in mean power (MP), peak power (PP), and fatigue index (FI) were compared between trials. MP was significantly increased in Cr 1-minute, Cr 3-minute, and Pl 6-minute groups (p < 0.05). Significant PP increases were demonstrated in Cr 1-minute and Pl 6-minute groups (p < 0.05), and FI significantly increased in Pl 1-minute group (p < 0.05). Results indicate that Cr supplementation is effective in improving recovery from repeated sprint cycling performances when the recovery interval is of a short (<6 minutes) duration.