Christopher C. Cheatham

Comparisons of cubed ice, crushed ice, and wetted ice on intramuscular and surface temperature changes

CONTEXT Many researchers have investigated the effectiveness of different types of cold application, including cold whirlpools, ice packs, and chemical packs. However, few have investigated the effectiveness of different types of ice used in ice packs, even though ice is one of the most common forms of cold application. OBJECTIVE To evaluate and compare the cooling effectiveness of ice packs made with cubed, crushed, and wetted ice on intramuscular and skin surface temperatures. DESIGN Repeated-measures counterbalanced design. SETTING Human performance research laboratory. PATIENTS OR OTHER PARTICIPANTS Twelve healthy participants (6 men, 6 women) with no history of musculoskeletal disease and no known preexisting inflammatory conditions or recent orthopaedic injuries to the lower extremities. INTERVENTION(S) Ice packs made with cubed, crushed, or wetted ice were applied to a standardized area on the posterior aspect of the right gastrocnemius for 20 minutes. Each participant was given separate ice pack treatments, with at least 4 days between treatment sessions. MAIN OUTCOME MEASURE(S) Cutaneous and intramuscular (2 cm plus one-half skinfold measurement) temperatures of the right gastrocnemius were measured every 30 seconds during a 20-minute baseline period, a 20-minute treatment period, and a 120-minute recovery period. RESULTS Differences were observed among all treatments. Compared with the crushed-ice treatment, the cubed-ice and wetted-ice treatments produced lower surface and intramuscular temperatures. Wetted ice produced the greatest overall temperature change during treatment and recovery, and crushed ice produced the smallest change. CONCLUSIONS As administered in our protocol, wetted ice was superior to cubed or crushed ice at reducing surface temperatures, whereas both cubed ice and wetted ice were superior to crushed ice at reducing intramuscular temperatures.

Cardiovascular responses during prolonged exercise at ventilatory threshold in boys and men

PURPOSE The purpose of this study was to examine the cardiovascular responses during prolonged exercise in boys and men at an intensity set relative to ventilatory threshold (VT). METHODS Eight boys (10-13 yr) and 10 men (18-25 yr) completed an orientation trial, a maximal exercise test, and a 40-min submaximal exercise bout at an intensity equal to the VO2 at VT (approximately 64.5% VO2max). RESULTS Heart rate (HR) was higher and stroke volume (SV) was lower in the boys compared with the men (P < or = 0.05). From 10 to 40 min, HR significantly increased 9.5% and 13.6% and SV significantly decreased 8.8% and 11.6% in the boys and men, respectively. Despite the tendency for the changes in HR and SV to be greater in the men, the group-by-time interaction was not significant. Cardiac output was greater in the men (P < or = 0.05) but remained constant over time (P > 0.05). In men, mean arterial blood pressure was higher (P < or = 0.05) and decreased 4.2% over time. In boys, mean arterial blood pressure remained constant, which resulted in a significant group-by-time interaction. Total peripheral resistance (TPR) was significantly higher in the boys and remained constant over time (P > 0.05). From 0 to 40 min, the decrease in plasma volume was significantly greater in the men (-10.2%) than the boys (-5.7%) but was unrelated to the changes in SV in either group (P > 0.05). CONCLUSION In conclusion, the cardiovascular responses during prolonged exercise are similar in boys and men, although there is a tendency for the magnitude of cardiovascular drift to be greater in the men.

Resistance Training for Adolescents

The benefits and possible detriment of resistance training have been noted extensively in the literature. Although the benefits of resistance training are well known, many professionals fail to heed scientific advice or follow appropriate recommendations for resistance training in adolescents. When developing a resistance training program for adolescents, be cognizant of any pre-existing health conditions and experience level of the adolescent. For strength training, the adolescent should begin with exercises that involve all major muscle groups with relatively light weight, one to three sets of 6 to 15 repetitions, 2 to 3 non-consecutive days per week. As the adolescent becomes more experienced, gradually increase loads and add multijoint exercises. Each exercise session should be properly supervised for safety, and to provide feedback on technique and form, regardless of the resistance training experience of the adolescent. This article reviews the guidelines for resistance training for health-related fitness for adolescents.

The immunological and metabolic responses to exercise of varying intensities in normoxic and hypoxic environments.

Blegen, M, Cheatham, C, Caine-Bish, N, Woolverton, C, Marcinkiewicz, J, and Glickman, E. The immunological and metabolic responses to exercise of varying intensities in normoxic and hypoxic environments. J Strength Cond Res 22(5): 1638-1644, 2008-The purpose of this study was to determine the effects of varying intensities of exercise in normoxic and hypoxic environments on selected immune regulation and metabolic responses. Using a within-subjects design, subjects performed maximal tests on a cycle ergometer in both normoxic (PiO2 = 20.94%) and hypoxic (PiO2 = 14.65%) environments to determine &OV0312;O2max. On separate occasions, subjects then performed four randomly assigned, 1-hour exercise bouts on a cycle ergometer (two each in normoxic and hypoxic environments). The hypoxic environment was created by reducing the O2 concentration of inspired air using a commercially available hypoxic chamber. The intensities for the exercise bouts were predetermined as 40 and 60% of their normoxic &OV0312;O2max for the normoxic exercise bouts and as 40 and 60% of their hypoxic &OV0312;O2max for the hypoxic exercise bouts. Blood samples were collected preexercise, postexercise, 15 minutes postexercise, 2 hours postexercise, and 24 hours postexercise for the determination of interleukin-1 (IL-1), tumor necrosis factor-α (TNF-α), glucose, glycerol, free fatty acids, epinephrine, norepinephrine, and cortisol. There were no significant differences (p < 0.05) between condition or intensity for IL-1 or TNF-α. Significant differences (p < 0.05) between intensities were demonstrated for epinephrine, norepinephrine, and cortisol (p < 0.05). A significant difference was identified between normoxic and hypoxic environments with respect to nonesterifed fatty acids (0.45 ± 0.37 vs. 0.58 ± 0.31 mEq·L−1, respectively; p = 0.012). During prolonged exercise at 40 and 60% of their respective &OV0312;O2max values, hypoxia did not seem to dramatically alter the response of the selected immune system or metabolic markers. Exercise training that uses acute hypoxic environments does not adversely affect immune regulation system status and may be beneficial for those individuals looking to increase endurance performance.

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.

Hierarchical Linear Model: Thinking Outside the Traditional Repeated-Measures Analysis-of-Variance Box

Longitudinal designs are common in the field of athletic training. For example, in the Journal of Athletic Training from 2005 through 2010, authors of 52 of the 218 original research articles used longitudinal designs. In 50 of the 52 studies, a repeated-measures analysis of variance was used to analyze the data. A possible alternative to this approach is the hierarchical linear model, which has been readily accepted in other medical fields. In this short report, we demonstrate the use of the hierarchical linear model for analyzing data from a longitudinal study in athletic training. We discuss the relevant hypotheses, model assumptions, analysis procedures, and output from the HLM 7.0 software. We also examine the advantages and disadvantages of using the hierarchical linear model with repeated measures and repeated-measures analysis of variance for longitudinal data.

Fluid Replacement Attenuates Physiological Strain Resulting From Mild Hypohydration Without Impacting Cognitive Performance

PURPOSE The impact of mild hypohydration on physiological responses and cognitive performance following exercise-heat stress (EHS) were examined compared with conditions when fluids were ingested ad libitum (AL) or replaced to match sweat losses (FR). METHODS Twelve unacclimatized, recreationally-active men (22.2 ± 2.4 y) completed 50 min cycling (60%VO2peak) in the heat (32°C; 65% RH) under three conditions: no fluid (NF), AL, and FR. Before and after EHS, a cognitive battery was completed: Trail making, perceptual vigilance, pattern comparison, match-to-sample, and letter-digit recognition tests. RESULTS Hypohydration during NF was greater compared with AL and FR (NF: -1.5 ± 0.6; AL: -0.3 ± 0.8; FR: -0.1 ± 0.3% body mass loss) resulting in higher core temperature (by 0.4, 0.5 °C), heart rate (by 13 and 15 b·min-1), and physiological strain (by 1.3, 1.5) at the end of EHS compared with AL and FR, respectively. Cognitive performance (response time and accuracy) was not altered by fluid condition; however, mean response time improved (p < .05) for letter-digit recognition (by 56.7 ± 85.8 ms or 3.8%; p < .05) and pattern comparison (by 80.6 ± 57.4 ms or 7.1%; p < .001), but mean accuracy decreased in trail making (by 1.2 ± 1.4%; p = .01) after EHS (across all conditions). CONCLUSIONS For recreational athletes, fluid intake effectively mitigated physiological strain induced by mild hypohydration; however, mild hypohydration resulting from EHS elicited no adverse changes in cognitive performance.

THE INFLUENCE OF ETHNICITY ON THERMOSENSITIVITY DURING COLD WATER IMMERSION

PURPOSE This investigation evaluated the influence of ethnicity, Caucasian (CAU) vs. African American (AA), on thermosensitivity and metabolic heat production (HP) during cold water immersion (20 degrees C) in 15 CAU (22.7 +/- 2.7 yr) vs. 7 AA (21.7 +/- 2.7 yr) males. METHODS Following a 20-min baseline period (BASE), subjects were immersed in 20 degrees C water until esophageal temperature (Tes) reached 36.5 degrees C or for a maximum pre-occlusion (Pre-OCC) time of 40 min. Arm and thigh cuffs were then inflated to 180 and 220 mm Hg, respectively, for 10 min (OCC). Following release of the inflated cuffs (Post-OCC), the slope of the relationship between the decrease in Tes and the increase in HP was used to define thermosensitivity (beta). RESULTS ANOVA revealed no significant difference in thermosensitivity between CAU and AA (CAU = 3.56 +/- 1.54 vs. AA = 2.43 +/- 1.58 W.kg(-1). degrees C(-1)). No significant differences (p > 0.05) were found for Tsk (CAU = 24.2 +/- 1.1 vs. AA = 25.1 +/- 1.1 degrees C) or HP (p > 0.05; CAU = 2.5 +/- 0.8 vs. AA = 36.5 +/- 1.8 W.kg(-1)). However, a significant (p < 0.05) main effect for ethnicity for Tes was observed (CAU = 36.7 +/- 1.8 vs. AA = 36.5 +/- 1.8 degrees C). CONCLUSION These data suggest, despite a differential response in Tes between AA and CAU groups, the beta of HP during cold water immersion is similar between CAU and AA. Therefore, these data demonstrate that when faced with a cold challenge, there is a similar response in HP between CAU and AA that is accompanied by a differential response in Tes.

Laboratory and Field Techniques for Measuring Performance

As a scientist, coach, athlete, or other fitness-type professional, knowledge of tests to measure specific physiologic characteristics that may ultimately contribute to performance in a sport or event is imperative. Baseline measurements of these factors influencing performance are critical for many different reasons. First, it is difficult to get to a predetermined end point if the baseline is unknown. Second, these specific physiologic characteristic, once measured, can be evaluated and used as a guide to develop appropriate training strategies for continued improvement. As such, this chapter explores and details the most widely used laboratory and field techniques used to measure human performance. Performance can be thought of as the way an individual or something functions. There are many levels of performance such as poor, average, or elite. Many times, performance is measured by the outcome of the game or event with wins and losses. So what determines an athlete’s ability to perform, or more importantly, excel at his or her sport? Of particular interest in this chapter are the physiologic components that comprise a portion of sport performance. Technical skill and tactical awareness are not considered here but are extremely important to overall sport performance. Certainly, genetic endowment is at the top of the list of physiologic parameters that affect sport performance. As has often been said, we must choose our parents wisely and realize that genetic predisposition to exercise performance is uncontrollable. Along with genetics, the overall health and nutritional status of an athlete can affect their performance. These factors of health and nutritional status are controllable and must be optimized. Another factor and arguably the most recognized influential and controllable component of performance is training. A tremendous amount of scientific study along with trial and error have produced increasingly better performances across the athletic spectrum through the improvement of training programs. A cornerstone to these improved training programs is the ability to monitor an athlete’s progress. This monitoring can be achieved by properly selecting and administering specific laboratory and field tests based on sport-specific physiologic demands.

The Effects of Nicotine on the Metabolic and Hormonal Responses During Acute Cold Exposure

Abstract Objective.—To examine the effects of nicotine on the metabolic and hormonal responses during acute cold exposure. Methods.—Participants in this study included 6 men and 5 women between the ages of 19 and 25 years. Each subject performed 2 cold-air trials (CATs) consisting of a 30-minute baseline (BASE) period and a 120-minute exposure to 10°C air. One CAT was performed after a nicotine (NIC) dosing using a 21-mg transdermal patch, whereas the other CAT was performed after a placebo (PL) treatment. Blood samples for metabolic and hormonal measurements were obtained at the end of BASE and immediately after the cold exposure. Results.—When examining the sexes separately, there was no difference in norepinephrine between PL and NIC (P = .066). There was also no difference in epinephrine between PL and NIC in either sex (P = .634). From BASE to 120 minutes of the CAT, there was a significant decrease in cortisol (P = .036), but this response was similar between the 2 treatments (P = .077). Glucose and glycerol concentrations were not different between the PL and NIC treatments. At BASE, nonesterified fatty acid (NEFA) concentration was lower during PL compared with NIC (P = .021); however, at 120 minutes of the CAT, NEFA was greater during PL compared with NIC (P = .035). Conclusions.—During 120 minutes of cold exposure, NIC resulted in alterations in the responses in NEFA, whereas the other blood measurements were not significantly different between the 2 groups.