Melissa W. Roti

Comparison of a Very Low-Carbohydrate and Low-Fat Diet on Fasting Lipids, LDL Subclasses, Insulin Resistance, and Postprandial Lipemic Responses in Overweight Women

Objective: Very low-carbohydrate diets are widely used for weight loss yet few controlled studies have determined how these diets impact cardiovascular risk factors compared to more traditional low-fat weight loss diets. The primary purpose of this study was to compare a very low-carbohydrate and a low-fat diet on fasting blood lipids, LDL subclasses, postprandial lipemia, and insulin resistance in overweight and obese women. Methods: Thirteen normolipidemic, moderately overweight (body fat >30%) women were prescribed two hypocaloric (−500 kcal/day) diets for 4 week periods, a very low-carbohydrate (<10% carbohydrate) and a low-fat (<30% fat) diet. The diets were consumed in a balanced and randomized fashion. Two fasting blood draws were performed on separate days and an oral fat tolerance test was performed at baseline, after the very low-carbohydrate diet, and after the low-fat diet. Results: Compared to corresponding values after the very low-carbohydrate diet, fasting total cholesterol, LDL-C, and HDL-C were significantly (p ≤ 0.05) lower, whereas fasting glucose, insulin, and insulin resistance (calculated using the homeostatic model assessment) were significantly higher after the low-fat diet. Both diets significantly decreased postprandial lipemia and resulted in similar nonsignificant changes in the total cholesterol/HDL-C ratio, fasting triacylglycerols, oxidized LDL, and LDL subclass distribution. Conclusions: Compared to a low-fat weight loss diet, a short-term very low-carbohydrate diet did not lower LDL-C but did prevent the decline in HDL-C and resulted in improved insulin sensitivity in overweight and obese, but otherwise healthy women. Small decreases in body mass improved postprandial lipemia, and therefore cardiovascular risk, independent of diet composition.

Influence of Hydration on Physiological Function and Performance During Trail Running in the Heat

CONTEXT Authors of most field studies have not observed decrements in physiologic function and performance with increases in dehydration, although authors of well-controlled laboratory studies have consistently reported this relationship. Investigators in these field studies did not control exercise intensity, a known modulator of body core temperature. OBJECTIVE To directly examine the effect of moderate water deficit on the physiologic responses to various exercise intensities in a warm outdoor setting. DESIGN Semirandomized, crossover design. SETTING Field setting. PATIENTS OR OTHER PARTICIPANTS Seventeen distance runners (9 men, 8 women; age = 27 +/- 7 years, height = 171 +/- 9 cm, mass = 64.2 +/- 9.0 kg, body fat = 14.6% +/- 5.5%). INTERVENTION(S) Participants completed four 12-km runs (consisting of three 4-km loops) in the heat (average wet bulb globe temperature = 26.5 degrees C): (1) a hydrated, race trial (HYR), (2) a dehydrated, race trial (DYR), (3) a hydrated, submaximal trial (HYS), and (4) a dehydrated, submaximal trial (DYS). MAIN OUTCOME MEASURE(S) For DYR and DYS trials, dehydration was measured by body mass loss. In the submaximal trials, participants ran at a moderate pace that was matched by having them speed up or slow down based on pace feedback provided by researchers. Intestinal temperature was recorded using ingestible thermistors, and participants wore heart rate monitors to measure heart rate. RESULTS Body mass loss in relation to a 3-day baseline was greater for the DYR (-4.30% +/- 1.25%) and DYS trials (-4.59% +/- 1.32%) than for the HYR (-2.05% +/- 1.09%) and HYS (-2.0% +/- 1.24%) trials postrun (P < .001). Participants ran faster for the HYR (53.15 +/- 6.05 minutes) than for the DYR (55.7 +/- 7.45 minutes; P < .01), but speed was similar for HYS (59.57 +/- 5.31 minutes) and DYS (59.44 +/- 5.44 minutes; P > .05). Intestinal temperature immediately postrun was greater for DYR than for HYR (P < .05), the only significant difference. Intestinal temperature was greater for DYS than for HYS postloop 2, postrun, and at 10 and 20 minutes postrun (all: P < .001). Intestinal temperature and heart rate were 0.22 degrees C and 6 beats/min higher, respectively, for every additional 1% body mass loss during the DYS trial compared with the HYS trial. CONCLUSIONS A small decrement in hydration status impaired physiologic function and performance while trail running in the heat.

Effect of chronic caffeine intake on choice reaction time, mood, and visual vigilance

The stimulatory effects of acute caffeine intake on choice reaction time, mood state, and visual vigilance are well established. Little research exists, however, on the effects of chronic caffeine ingestion on psychomotor tasks. Therefore, the purpose of this study was to evaluate the effects of 5 days of controlled caffeine intake on cognitive and psychomotor performance. Three groups of 20 healthy males (age=22+/-3 years, mass=75.4+/-7.9 kg, body fat percentage=11.2+/-5.1%) twice completed a battery of cognitive and psychomotor tasks: after 6 days of 3 mg.kg(-1) day(-1) caffeine equilibration (Day 6), and after 5 days of experimental (0 [G0], 3 [G3], or 6 [G6] mg.kg(-1) day(-1)) caffeine intake (Day 11). Groups were randomized and stratified for age, mass, and body composition; all procedures were double-blind. Cognitive analyses involved a visual four-choice reaction time test, a mood state questionnaire, and a visual vigilance task. Experimental chronic caffeine intake did not significantly alter the number of correct responses or the mean latency of response for either the four-choice reaction time or the visual vigilance tasks. The Vigor-Activity subset of the mood state questionnaire was significantly greater in G3 than G0 or G6 on Day 11. All other mood constructs were unaffected by caffeine intake. In conclusion, few cognitive and psychomotor differences existed after 5 days of controlled caffeine ingestion between subjects consuming 0, 3, or 6 mg.kg(-1) day(-1) of caffeine, suggesting that chronic caffeine intake (1) has few perceptible effects on cognitive and psychomotor well-being and (2) may lead to a tolerance to some aspects of caffeines acute effects.

Examining the influence of hydration status on physiological responses and running speed during trail running in the heat with controlled exercise intensity.

Lopez, RM, Casa, DJ, Jensen, KA, DeMartini, JK, Pagnotta, KD, Ruiz, RC, Roti, MW, Stearns, RL, Armstrong, LE, and Maresh, CM. Examining the influence of hydration status on physiological responses and running speed during trail running in the heat with controlled exercise intensity. J Strength Cond Res 25(11): 2944–2954, 2011—The purpose of this study was to determine the effects of dehydration at a controlled relative intensity on physiological responses and trail running speed. Using a randomized, controlled crossover design in a field setting, 14 male and female competitive, endurance runners aged 30 ± 10.4 years completed 2 (hydrated [HY] and dehydrated [DHY]) submaximal trail runs in a warm environment. For each trial, the subjects ran 3 laps (4 km per lap) on trails with 4-minute rests between laps. The DHY were fluid restricted 22 hours before the trial and during the run. The HY arrived euhydrated and were given water during rest breaks. The subjects ran at a moderate pace matched between trials by providing pacing feedback via heart rate (HR) throughout the second trial. Gastrointestinal temperature (TGI), HR, running time, and ratings of perceived exertion (RPE) were monitored. Percent body mass (BM) losses were significantly greater for DHY pretrial (−1.65 ± 1.34%) than for HY (−0.03 ± 1.28%; p < 0.001). Posttrial, DHY BM losses (−3.64 ± 1.33%) were higher than those for HY (−1.38 ± 1.43%; p < 0.001). A significant main effect of TGI (p = 0.009) was found with DHY having higher TGI postrun (DHY: 39.09 ± 0.45°C, HY: 38.71 ± 0.45°C; p = 0.030), 10 minutes post (DHY: 38.85 ± 0.48°C, HY: 38.46 ± 0.46°C; p = 0.009) and 30 minutes post (DHY: 38.18 ± 0.41°C, HY: 37.60 ± 0.25°C; p = 0.000). The DHY had slower run times after lap 2 (p = 0.019) and lap 3 (p = 0.025). The DHY subjects completed the 12-km run 99 seconds slower than the HY (p = 0.027) subjects did. The RPE in DHY was slightly higher than that in HY immediately postrun (p = 0.055). Controlling relative intensity in hypohydrated runners resulted in slower run times, greater perceived effort, and elevated TGI, which is clinically meaningful for athletes using HR as a gauge for exercise effort and performance.

Influence of betaine consumption on strenuous running and sprinting in a hot environment.

This investigation evaluated the effects of a nutritional supplement (the organic osmolyte betaine) in rehydration solutions, with and without carbohydrate and electrolytes. Ten male runners ((mean ± SD) age, 20 ± 2 years; weight, 70.6 ± 6.8 kg; maximal aerobic power, 63.5 ± 4.1 mL O2·kg−1·min−1) dehydrated to −2.7% of body weight. They next rehydrated to −1.4% of body weight by consuming 1 L fluid during each of four experiments (double-blind, randomized, cross-over design): flavored, non-caloric water (W); W + 5 g·L−1 betaine (W+B); 6% carbohydrate-electrolyte fluid (C); or C + 5 g·L−1 betaine (C+B). Subjects then performed prolonged treadmill running (75 minutes at 65%&OV0312;o2max) plus a performance sprint to volitional exhaustion (3.1-3.8 minutes at 84%&OV0312;o2max) in an environmental chamber (31.1°C, 88.0°F). Only W versus W+B and C versus C+B statistical comparisons were germane to the research questions. Observations indicated that rehydration with fluids containing betaine resulted in significant differences (p < 0.05) of plasma volume, oxygen consumption, plasma lactate concentration, and thermal sensation. The present experiments did not support the use of betaine to improve sprint duration, but nonsignificant trends occurred when betaine trials were compared with non-betaine trials (mean C+B > C by 32 seconds, +16%; mean W+B > W by 38 seconds, +21%). We interpret the increases of both aerobic and anaerobic metabolism (C+B > C) to mean that further investigation of betaine as a nutritional supplement, using other types of exercise, is warranted.

Comparison of Two Fluid Replacement Protocols During a 20-km Trail Running Race in the Heat.

Abstract Lopez, RM, Casa, DJ, Jensen, K, Stearns, RL, DeMartini, JK, Pagnotta, KD, Roti, MW, Armstrong, LE, and Maresh, CM. Comparison of two fluid replacement protocols during a 20-km trail running race in the heat. J Strength Cond Res 30(9): 2609–2616, 2016—Proper hydration is imperative for athletes striving for peak performance and safety, however, the effectiveness of various fluid replacement strategies in the field setting is unknown. The purpose of this study was to investigate how two hydration protocols affect physiological responses and performance during a 20-km trail running race. A randomized, counter-balanced, crossover design was used in a field setting (mean ± SD: WBGT 28.3 ± 1.9° C). Well-trained male (n = 8) and female (n = 5) runners (39 ± 14 years; 175 ± 9 cm; 67.5 ± 11.1 kg; 13.4 ± 4.6% BF) completed two 20-km trail races (5 × 4-km loop) with different water hydration protocols: (a) ad libitum (AL) consumption and (b) individualized rehydration (IR). Data were analyzed using repeated measures ANOVA. Paired t-tests compared pre-race–post-race measures. Main outcome variables were race time, heart rate (HR), gastrointestinal temperature (TGI), fluid consumed, percent body mass loss (BML), and urine osmolality (Uosm). Race times between groups were similar. There was a significant condition × time interaction (p = 0.048) for HR, but TGI was similar between conditions. Subjects replaced 30 ± 14% of their water losses in AL and 64 ± 16% of their losses in IR (p < 0.001). Ad libitum trial experienced greater BML (−2.6 ± 0.5%) compared with IR (−1.3 ± 0.5%; p < 0.001). Pre-race to post-race Uosm differences existed between AL (−273 ± 146 mOsm) and IR (−145 ± 215 mOsm, p = 0.032). In IR, runners drank twice as much fluid than AL during the 20-km race, leading to > 2% BML in AL. Ad libitum drinking resulted in 1.3% greater BML over the 20-km race, which resulted in no thermoregulatory or performance differences from IR.

Regional Surface Electromyography of the Vastus Lateralis During Strength and Power Exercises

Abstract Earp, JE, Stucchi, DT, DeMartini, JK, and Roti, MW. Regional surface electromyography of the vastus lateralis during strength and power exercises. J Strength Cond Res 30(6): 1585–1591, 2016—Neuromuscular activation during and chronic adaptation from exercise are innately linked and both can vary along a muscles length. During high-force and high-speed exercise, intramuscular hypertrophy follows set patterns that provide the greatest biomechanical advantages. However, it is unknown if muscle activity as recorded by surface electromyography (sEMG) will follow these patterns. The purpose of the present study was to compare vastus lateralis intramuscular sEMG during the heavy squat (HS) and unloaded jump squat (JS) exercises. Ten subjects performed HS with 80% of maximum load and unloaded JS to parallel-depth, while intramuscular peak sEMG and mean sEMG were measured at 33% (proximal), 50% (middle), and 67% (distal) thigh length. Muscle activity was compared between regions and exercises using a 3 × 2 repeated measures ANOVA with Bonferoni post hoc corrections. Peak sEMG was greater proximally in JS than HS (p = 0.033), but similar in the middle and distal regions (p = 0.521, 0.594, respectively), whereas mean sEMG was similar between all regions (p = 0.150–0.979). In addition, a main effect was found in which peak and mean sEMG were greater proximally than the middle and distal regions (p = 0.001, 0.006). Muscle activity measured using sEMG displayed dissimilar patterns to previously observed regional hypertrophy. Specifically, although previous research found greater proximal hypertrophy in JS than HS, in the present study peak sEMG was greater in HS than JS. Furthermore, distally where HS elicited greater hypertrophy than JS, no differences in sEMG were present. Thus, regional sEMG appears not to be a viable tool for predicting differences in regional hypertrophy, most likely due to technological constraints and intramuscular differences in muscle structure.