E. L. Glickman-Weiss

Chronic stretching and running economy

Research demonstrates an inverse relationship between the range of motion of selected joint movements (flexibility) and running economy. Since stretching exercises have been shown to increase joint range of motion, stretching exercises may be contraindicated for endurance running performance. Hence, this study investigated the influence of a 10‐week program of stretching exercises on the oxygen costs of a 10 min sub‐maximal (approx. 70% peak VO2) treadmill run. Thirty‐two (16 female, 16 male) physically active, treadmill accommodated, college students participated in the study. All participants maintained their current activity level, with half the participants (8 female, 8 male) adding a 40 min, 3 days per week session of thigh and calf muscle stretching exercises. After 10 weeks, the stretching group (STR) exhibited a significant (P<0.05) increase (3.1±2.2 cm) in the sit‐and‐reach, while the non‐stretching group (CON) experienced no significant (P>0.05) change (0.0±0.4 cm). However, neither the STR nor the CON exhibited a significant (P>0.05) change in the O2 cost for the submaximal run. It is concluded, therefore, that a chronic stretching program does not necessarily negatively influence running economy.

Creatine supplementation alters the response to a graded cycle ergometer test.

Abstract To determine the effects of creatine supplementation on cardiorespiratory responses during a graded exercise test (GXT) 36 trained adults (20 male, 16 female; 21–27 years old) performed two maximal GXTs on a cycle ergometer. The first GXT was done in a non-supplemented condition, and the second GXT was done following 7 days of ingesting either 5 g creatine monohydrate, encased in gelatin capsules, four times daily (CS, 13 male, 6 female), or the same number of glucose capsules (PL, 7 male, 10 female). CS significantly (P < 0.05) improved total test time [pre-CS=1217 (240) s, mean (std. dev.) versus post-CS=1289 (215) s], while PL administration had no effect (P > 0.05) on total test time [pre-PL=1037 (181) s versus post-PL=1047 (172) s]. In addition, both oxygen consumption (V˙O2) and heart rate at the end of each of the first five GXT stages were significantly lower after CS, but were unchanged after PL. Moreover, the ventilatory threshold occurred at a significantly greater V˙O2 for CS [pre-CS=2.2 (0.4) l · min−1 or 66% of peak V˙O2 versus post-CS=2.6 (0.5) l · min−1 or 78% of peak V˙O2; pre-PL=2.6 (0.9) l · min−1 or 70% peak V˙O2 versus post-PL=2.6 (1.1) l · min−1 or 68% of peak V˙O2]. Neither CS nor PL had an effect on peak V˙O2 [pre-CS=3.4 (0.7) l · min−1 versus post-CS=3.3 (0.7) l · min−1; pre-PL=3.7 (1.1) l · min−1 versus post-PL=3.7 (1.1) l · min−1]. Apparently, CS can alter the contributions of the different metabolic systems during the initial stages of a GXT. Thus, the body is able to perform the sub-maximal workloads at a lower oxygen cost with a concomitant reduction in the work performed by the cardiovascular system.

A thermal perception scale for use during resting exposure to cold air.

The present investigation introduces a thermal perception scale (TS) for use during protracted resting cold exposure. The scale contains categories ranging consecutively from 0, i.e., Nothing at all, to 10, i.e., Very, very cold. Eight Caucasian men were randomly exposed to ambient air in a climatically controlled environmental chamber of 8°, 12°, and 27° C for 120 min. on 3 separate occasions and monitored for rectal temperature (Tre), mean skin temperature (T̄sk), ventilation (VE), and oxygen consumption (VO2). The terminal perceptual categories were anchored for 8 subjects and a standard set of instructions was presented prior to each trial. The anchor Temperature was the room air in the anteroom which was 27° C, representing 0, i.e., “Nothing at all,” to extend the scale so that subsequent judgments on the scale were expressed in relation to this category. In addition, the subjects were also asked to imagine the coldest that they have ever experienced and this was designed to anchor “Very, very cold.” The relations between scale scores and the thermoregulatory variables were examined wirh a simple linear regression and coefficients of correlation and determination for each subject. High coefficients of determination between T̄sk, VO2, and VE indicated that, for individual subjects, the scores on the scale were related to VE, T̄sk, and VO2. High reliability coefficients for TS were also reported. In addition, the ratings and VO2 relation tended to be similar between subjects. Therefore, this scale appears to be a valid and reliable tool for measuring the perception of cold when at rest in air.

A SUBMAXIMAL TREADMILL TEST FOR DEVELOPING TARGET RATINGS OF PERCEIVED EXERTION FOR OUTPATIENT CARDIAC REHABILITATION

For patient populations whose heart rates cannot be used to regulate exercise intensity, the Borg Rating of Perceived Exertion (RPE) Scale is the preferred way to prescribe exercise intensity. Individual perceptual variations are best quantified by measuring perceptual intensity during maximal exercise testing; however, many situations require a submaximal protocol. Here, a submaximal treadmill procedure for establishing individualized target Ratings of Perceived Exertion is described. Target ratings of exertion were developed for outpatient cardiac rehabilitation patients using the new method and compared to target Ratings of Perceived Exertion obtained using standard techniques. A total of 144 target ratings at intensities ranging from 50% to 85% VO2max were compared. Over-all, the average difference between the two methods was 0.27 units and was not significant at any intensity. Therefore, the Treadmill Slope Method appears to be a valid submaximal test for generating target Ratings of Perceived Exertion for outpatient cardiac rehabilitation patients.

Three-point method of prescribing exercise with ratings of perceived exertion is valid for cardiac patients.

It is often difficult to use heart rate to prescribe exercise for cardiac patients due to the effects of medications and procedures such as cardiac transplantation. Ratings of Perceived Exertion (RPE) is the preferred method of regulating exercise intensity in these situations. An RPE-based exercise prescription has previously depended on perceptual data from a maximal Graded Exercise Test (GXT). Recently, using 13 healthy subjects, we validated a Three-point RPE for prescribing exercise using RPE which can be used when ratings from a GXT are not available. Currently, we examined the accuracy of this method for developing target RPEs for patients in Phase II cardiac rehabilitation. Such target RPEs did not differ from those obtained using standard procedures. We conclude that the Three-point Method is valid for preparing RPE-based exercise prescriptions for Phase II cardiac rehabilitation patients.

The effect of capsaicin on the thermal and metabolic responses of men exposed to 38°C for 120 minutes.

Objective To determine the thermoregulatory response of humans to heat following an ingestion of capsaicin. Methods The thermoregulatory responses of 7 men (aged 22–28 years) to a 2-hour exposure to 38°C (50% relative humidity) were compared following ingestion of either placebo or capsaicin. The capsaicin dose (2mg·kg −1 ) was ingested 1 hour prior to the heat exposure, and all subjects were encouraged to overhydrate for 48 hours prior to each trial. Core temperature, mean skin temperature, cardiac output, and oxygen consumption were measured every 30 minutes. In addition, the changes (pre-exposure vs postexposure) in body mass and plasma volume were calculated. Results As expected, core temperature, cardiac output, and oxygen consumption all increased significantly ( P (P >.05) between the placebo and capsaicin trials, except for mean skin temperature. The treatment effect for mean skin temperature was significant (P =.013), with the capsaicin response (34.7°C) registering lower than the placebo measurement (35.1°C). Conclusions It appears that humans respond differently than animals to capsaicin ingestion. For humans, ingesting a 2-mg·kg −1 dose of capsaicin 1 hour prior to heat exposure does not alter a persons ability to thermoregulate in the heat.

The effects of gender and menstrual phase on carbohydrate utilization during acute cold exposure.

OBJECTIVE The purpose of this study was to evaluate the effects of gender and menstrual cycle on the percent of carbohydrate (CHO) utilized during cold water immersion (20 degrees C). Previous research has suggested that males and females utilize CHO differently during submaximal exercise. This study examined whether this differential response is replicated during a submaximal elevation in metabolism, as demonstrated during thermogenesis (i.e., shivering during acute cold exposure). METHODS Male and female subjects between the ages of 18 and 30 years were recruited for this study. Female subjects underwent the experimental trial once during the follicular phase and once during the luteal phase of their menstrual cycle. Subjects were immersed to the first thoracic vertebra until esophageal temperature reached 36.5 degrees C or for a maximum preocclusion period of 40 minutes. Peripheral temperature homeostasis via cuff occlusion (right arm and left leg) took place for 10 minutes, after which the pressure cuffs were released (postocclusion) and the subjects remained in the water for an additional 10 minutes. The following variables were measured: respiratory exchange ratio, percent of CHO utilization, and oxygen consumption (Vo2). RESULTS Analysis of variance demonstrated no significant difference between genders or phases of the menstrual cycle in respiratory exchange ratio, percent CHO utilization, or Vo2 during cold water immersion. A significant difference was observed between men and women for absolute Vo2. CONCLUSIONS These data suggest that although men and women differ with respect to absolute aerobic metabolism, this distinction does not cause a differential response with respect to substrate utilization during acute cold exposure.

Thermal sensation and substrate utilization differs among low- and high-fat women exposed to 17°C water

Objective Thermal sensation and the physiological responses of women (follicular phase) exposed to 17°C immersion for 120 minutes were investigated. Methods The subjects were divided into 2 groups by percent body fat (low fat [LF] = 21%±2% [mean ± SD] vs high fat [HF] = 30%±3%). A 2-way analysis of variance was used to determine differences between the groups in metabolism, metabolism derived from carbohydrate, metabolism derived from fat, blood glucose, rectal temperature, skin temperature, and thermal sensation. Results As anticipated, pooled metabolism increased across the 120-minute immersion. Metabolism derived from carbohydrate was significantly higher in the LF than in the HF group and increased across time. Blood glucose decreased significantly across time, yet there was no group difference, suggesting that the LF group may have utilized a greater proportion of intramuscular glycogen. The HF group demonstrated a higher rectal temperature compared to their LF counterparts. Overall, rectal temperature demonstrated a group × time interaction as immersion continued. However, rectal temperature for all subjects remained above 35°C. Surprisingly, the HF group perceived significantly greater thermal discomfort than did their LF counterparts. Conclusions Since intramuscular glycogen utilization is associated with shivering thermogenesis, the suspected greater utilization of this fuel by the LF group may have contributed to less thermal discomfort than in the HF group. However, since glycogen utilization was not directly measured, this speculation cannot be validated. It is also possible that the modified thermal sensation scale we used may not be an adequate marker of thermal discomfort in females with a high percentage of body fat (28% to 35%) exposed to cold water immersion.

Relationship between thermoregulatory parameters and DEXA-estimated regional fat

The present investigation utilized dual-energy X-ray absorptiometry (DEXA) as a means of assessing the relation between regional percent body fat and selected thermoregulatory variables. Tissue insulation (I) , rectal temperature ( T re ), mean skin temperature ( T ¯ sk ), and regional distribution of fat (i.e., arm, leg, trunk, abdomen) were examined utilizing a sample of seven Caucasian males ( X ¯ ± SE age=23.7 ± 1.9 years) who were exposed to 8°C air for 120 min. The strongest relationships between I , T ¯ sk , T re , and the fatness variables were determined utilizing the all-possible regressions procedure. The strongest relationship existed between the combination of abdominal and leg adiposity and I ( R 2 = 0.958, p T ¯ sk was described using the linear combination of trunk, abdominal, and arm fatness ( R 2 = 0.979, p T re used the combination of trunk, abdominal, and leg fatness ( R 2 = 0.946, p > .05). Based on these data utilizing the DEXA, one may describe important relationships between thermoregulatory variables and distribution of percent fat. Also, abdominal fatness was repeatedly influential in describing relationships between body fatness and thermoregulatory variables.

Does shivering thermogenesis enhance the individual's ability to maintain rectal temperature during immersion in cold water?

Shivering thermogenesis may enable individuals to maintain rectal temperature during acute cold exposure. This data analysis revisited this hypothesis and compared previously published data with unpublished data from our laboratory on those subjects that were terminated from cold water immersion early because of a reduction in rectal temperature (T(re)) - 35 degrees C. T(re), mean skin temperature (T(sk)), and oxygen uptake (VO2) were recorded at 5, 30, 60, and 90 min of immersion and were used to calculate 3delta readings for each exposure, that is, deltaT(30) minus T5, T60 minus T(30), and T(90) minus T(60). Single group t-tests were used to examine differences in deltaT(re), deltaT(sk), and deltaVO2 between the published data (PD) group and the individual subjects who were terminated early (TE) at each of three water temperatures (18 degrees C, 22 degrees C, 26 degrees C). For deltaVO2 the TE subjects were dichotomized by fatness (low percent fat, 8%-12%; or high percent fat, 18%-22%) to account for the VO2 differences between these groups (i.e., fatness) during cold water immersion. deltaT(re) was significantly (p < 0.05) decreased in TE subjects compared with PD subjects at all timepoints for 18 degrees C and 26 degrees C. At 22 degrees C, the TE subject exhibited a significantly greater (p < 0.05) decrease in deltaT(re) than the PD group at 90 min of immersion only. No significant (p > 0.05) differences in deltaT(sk) between the PD and TE groups were detected for any of the exposure temperatures over all time points. No difference (p > 0.05) between PD subjects and TE subjects for deltaVO2 was exhibited at any time point at any temperature. It appears that with respect to the TE group, elevations in VO2 were comparable to the PD group, but the TE group was unable to maintain T(re) during cold water immersion. In conclusion, from these data it appears that shivering thermogenesis does in part enhance the individuals ability to maintain T(re); however, as evidenced in the TE group, it also appears that the alterations in shivering thermogenesis for certain individuals may not be great enough to offset heat loss.