Stephen F. Crouse’s research while affiliated with Texas A&M University and other places

Choline plays many important roles, including the synthesis of acetylcholine, and may affect muscle responses to exercise. We previously observed correlations between low choline intake and reduced gains in strength and lean mass following a 12-week resistance exercise training (RET) program for older adults. To further explore these findings, we conducted a randomized controlled trial. Three groups of 50-to-69-year-old healthy adults underwent a 12-week RET program (3x/week, 3 sets, 8–12 reps, 70% of maximum strength (1RM)) and submitted >48 diet logs (>4x/week for 12 weeks). Participants’ diets were supplemented with 0.7 mg/kg lean/d (low, n = 13), 2.8 mg/kg lean/d (med, n = 11), or 7.5 mg/kg lean/d (high, n = 13) of choline from egg yolk and protein powder. The ANCOVA tests showed that low choline intake, compared with med or high choline intakes, resulted in significantly diminished gains in composite strength (leg press + chest press 1RM; low, 19.4 ± 8.2%; med, 46.8 ± 8.9%; high, 47.4 ± 8.1%; p = 0.034) and thigh-muscle quality (leg press 1RM/thigh lean mass; low, 12.3 ± 9.6%; med/high, 46.4 ± 7.0%; p = 0.010) after controlling for lean mass, protein, betaine, and vitamin B12. These data suggest that low choline intake may negatively affect strength gains with RET in older adults.

Red meat is stigmatized as an unhealthy protein choice; however, its impacts on vascular function have not been evaluated. We aimed to measure the vascular impact of adding either low-fat (~5% fat) ground beef (LFB) or high-fat (~25% fat) ground beef (HFB) to a habitual diet in free-living men. Twenty-three males (39.9 ± 10.8 years, 177.5 ± 6.7 cm, 97.3 ± 25.0 kg) participated in this double-blind crossover study. Assessment of vascular function and aerobic capacity were measured at entry and in the last week of each intervention and washout period. Participants then completed two 5-week dietary interventions (LFB or HFB; 5 patties/week) in a randomized order with a 4-week washout. Data were analyzed via 2 × 2 repeated-measures ANOVA (p < 0.05). The HFB intervention improved FMD relative to all other time points, while lowering systolic (SBP) and diastolic blood pressure (DBP) relative to entry. Neither the HFB nor the LFB altered pulse wave velocity. The addition of either low- or high-fat ground beef did not negatively alter vascular function. In fact, consuming HFB improved FMD and BP values, which may be mediated by lowering LDL-C concentrations.

We hypothesized that consumption of high-fat (HF) ground beef (24% fat) would not affect plasma concentrations of high-density lipoprotein cholesterol (HDL-C) or low-density lipoprotein (LDL-C), whereas low-fat (LF) ground beef (5% fat) would decrease HDL-C and LDL-C concentrations. In a randomized 2-period crossover, controlled feeding trial, 25 men (mean age and body mass index, 40 years and 31.2) consumed 115-g HF or LF patties, 5/week for 5 weeks with a 4-week washout. The HF treatment increased % energy from fat (p = 0.006) and saturated fat (p = 0.004) and tended (p = 0.060) to depress % energy from carbohydrates. The HF and LF treatments decreased the plasma concentrations of HDL-C (p = 0.001) and LDL-C (p = 0.011). Both ground beef treatments decreased the abundance of HDL3a and increased the abundance of HDL3 (p ≤ 0.003); the LF treatment also decreased the abundance of HDL2b and HDL2a (p ≤ 0.012). The HF and LF treatments decreased the abundance of LDL3 and LDL4 (p ≤ 0.024) and the HF treatment also decreased LDL5 (p = 0.041). Contrary to our hypothesis, the HF treatment decreased plasma HDL-C and LDL-C concentrations despite increased saturated fat intake, and both treatments decreased the abundance of smaller, denser LDL subfractions.

Objectives Choline is an essential micronutrient for many physiological processes related to exercise training including biosynthesis of acetylcholine. Though dietary choline intake has been studied in relation to endurance training and performance, none have studied it during resistance exercise training (RET) in older adults. The objective of the study was to examine the relationship between choline intake and muscle responses to RET in older adults. Methods Forty-six, 60–69-year-old individuals (M=19, F=27) underwent 12 weeks of RET (3x/week, 3 sets, 8–12 reps, 75% of maximum strength [1RM], 8 exercises). Body composition (DEXA) and 1RM tests were performed before and after training. After analyzing 1,656 diet logs (3x/week, 46 participants, 12 weeks), participants’ mean choline intakes were categorized into three groups: Low (2.9–5.5 mg/kg lean/d), Med-Low (5.6–8.0 mg/kg lean/d), or Adequate (8.1–10.6 mg/kg lean/d). These correspond to <50%, ∼63%, and ∼85% of Adequate Intake (AI) for choline, respectively. Results Gains in composite strength (leg press + chest press 1RM) were significantly lower in the Low group compared with the other groups (Low: 30.9 ± 15.1%, Med-Low: 70.3 ± 48.5%, Adequate: 81.9 ± 68.4%; p=0.004). ANCOVA with cholesterol, protein, or other nutrients did not alter this result. Reduced gains in lean mass were also observed in the Low group, compared with higher choline intake of 5.6–10.6 mg/kg lean/d (1.3 ± 0.6% vs. 3.2 ± 0.6%, p<0.05). Conclusion These data suggest that this population of older adults does not consume adequate choline and lower choline intake is negatively and independently associated with muscle responses to RET.

The purpose of this study was to develop an equation to predict strength for seven common resistance training exercises using anthropometric and demographic measures. One-hundred forty-seven healthy adults (74 males, 73 females, 35±12yr, 174±10cm, 88±19kg) volunteered to participate. Body composition values (regional/total) and body dimensions were assessed using dual-energy x-ray absorptiometry (DEXA). Subjects underwent maximal strength assessment for: Leg Press, Chest Press, Leg Curl, Lat Pulldown, Leg Extension, Triceps Pushdown, and Biceps Curl. Multiple linear regression with stepwise removal was used to determine the best model to predict maximal strength for each exercise. Independent predictor variables identified (p<0.05) were height (cm); weight (kg); BMI; age; sex (0=F,1=M); regional lean masses (LM,kg); fat mass (FM,kg); fat free mass (FFM,kg); percent fat (%BF); arm, leg, and trunk lengths (AL, LL, TL;cm); and shoulder width (SW,cm). Analyses were performed with and without regional measures to accommodate scenarios where DEXA is unavailable. All models presented were significant (p<0.05, R2=0.68-0.83), with regional models producing the greatest accuracy. Results indicate that maximal strength for individual resistance exercises can be reasonably estimated in adults.

We tested a PEEP (4.2 cmH2O) mouthpiece (PMP) on maximal cycling performance in healthy adults. Experiment-1, PMP vs. non-PMP mouthpiece (CON) [N=9 (5♂), Age=30±2 yr]; Experiment-2, PMP vs. no mouthpiece (NMP) [N=10 (7♂), Age=27±1 yr]. At timepoint 1 in both experiments (mouthpiece condition randomized) subjects performed graded cycling testing (GXT) (Corival® cycle ergometer) to determine V˙O2peak (ml*kg*min⁻¹), O2pulse (mlO2*bt⁻¹ ), GXT endurance time (GXT-T(s)), and V˙O2(ml*kg*min⁻¹)-at-ventilatory-threshold (V˙O2 @VT). At timepoint 2 72 h later, subjects completed a ventilatory-threshold-endurance-ride [VTER(s)] timed to exhaustion at V˙O2 @VT power (W). One week later at timepoints 3 and 4 (time-of-day controlled), subjects repeated testing protocols under the alternate mouthpiece condition. Selected results (paired T-test, *<0.05): Experiment 1 PMP vs. CON, respectively: V˙O2peak= 45.2±2.4* vs. 42.4±2.3; V˙O2@VT= 33.7±2.0 vs. 32.3±1.6; GXT-TTE=521.7±73.4* vs. 495.3±72.8; VTER=846.2±166.0 vs. 743.1±124.7; O2pulse=24.5±1.4* vs. 23.1±1.3. Experiment 2 PMP vs. NMP, respectively: V˙O2peak=43.3±1.6* vs. 41.7±1.6; V˙O2@VT=31.1±1.2* vs. 29.1±1.3; GXT-TTE=511.7*±49.6 vs. 486.4±49.6; VTER 872.4±134.0 vs. 792.9 ± 122.4; O2pulse=24.1±0.9* vs. 23.4±0.9. Results demonstrate that the PMP conferred a significant performance benefit to cyclists completing high intensity cycling exercise.