The purpose of this randomized controlled clinical trial was to determine the effect of a 14-week high-intensity interval training (HIIT) intervention with weight stability on metabolic flexibility, insulin sensitivity, and cardiorespiratory fitness in sedentary, premenopausal, nondiabetic, overweight/obese African American women. Twenty-eight subjects were allocated to one of two groups: HIIT, which performed three sessions per week of four high-intensity cycling intervals, or a control group (CON), which maintained their normal level of physical activity. Diet was controlled for all subjects to ensure weight stability. Pre- and postintervention (pre/post), subjects completed an incremental cycling test to limit of tolerance and, following a 10-day high-fat controlled feeding period, a euglycemic-hyperinsulinemic clamp to determine insulin sensitivity and substrate oxidation. Nine members of HIIT (age, 29 ± 4 yr; body mass, 90.1 ± 13.8 kg) and eleven members of CON (age, 30 ± 7 yr; body mass, 85.5 ± 10.7 kg) completed the study. HIIT experienced an increased limit of tolerance (post, 1,124 ± 202 s; pre, 987 ± 146 s; P < 0.05), gas exchange threshold (post, 1.29 ± 0.34 liters/min; pre, 0.97 ± 0.23 liters/min; P < 0.05), and fat oxidation at the same absolute submaximal work rate compared with CON (P < 0.05 for group-by-time interaction in all cases). However, changes in peak oxygen consumption (V̇o2peak), insulin sensitivity, free fatty acid suppression during insulin stimulation, and metabolic flexibility were not different in HIIT compared with CON. High-intensity interval training with weight stability increased exercise fat oxidation and tolerance in subjects at risk for diabetic progression, but did not improve insulin sensitivity or fat oxidation in the postabsorptive or insulin-stimulated state.

SUMMARY— The effects of temperature and humidity on postmortem and associated muscle properties during growth of “stress susceptible” pigs were evaluated. Exposure to ambient temperatures of 32 and 21°C for alternating 3‐day periods caused rapid post‐mortem glycolysis, high percent light reflectance, and increased light to dark fiber ratios in the longissimus dorsi muscle as compared to constant (27°C) temperature, but only in moderate (38–42% relative) humidity environments. The above events due to temperature acclimation were masked when the humidity was low (17–23% relative). Humidity effects that were independent of temperature acclimation resulted in high percent light reflectance and high muscle temperature in the post‐mortem muscle of pigs reared in low humidity. No significant differences were found in lactic dehydrogenase or succinic dehydrogenase enzyme activities of longissimus dorsi or gluteus medius muscles.

Suppressed development of edible portion in carcasses from cattle fed hay during the early feeding period (216-340 kg live weight) was followed by compensatory growth during the intermediate (341-409 kg live weight) and final (410-454 kg live weight) periods. However, when silage in the early feeding period was followed by corn concentrate in the intermediate period, no increased 'edible portion' development was achieved beyond that produced by continuous silage. The final feeding period (corn concentrate) resulted in a decline in ' edible portion' percentage in cattle that previously received concentrate in the intermediate period whereas those that previously received silage remained at about the same percentage.Cattle fed hay during the early period had less (P < 0-01) carcass weight, less (P< 0'01) fat cover, and more (P < 0-01) reticulo-rumen weight than those fed corn silage for the same period, regardless of slaughter weight.In the heavy (409 and 454 kg) slaughter groups, cattle fed silage in the early period had higher (P < 0-05) marbling scores than those fed hay. Feeding silage in the intermediate period resulted in lower colour (P < 0-01) and firmness (P < 0-01) scores in the longissimus dorsi muscle than feeding concentrate at that time. The dietary regimes used in these studies resulted in widely varying growth rates among treatments with consequential differences in the average age of the animal groups at slaughter. Therefore, the treatment effects observed seem to be easily explicable on the basis of age differences.

SUMMARYStudies were conducted on the muscle properties of pigs reared in one of several combinations of environmental temperature and humidity. Longissimus dorsi muscle of pigs reared in alternating temperatures (29 and 18°C) was inferior in structure to that of pigs reared in 29 or 18°C constant temperatures if the relative humidity was low (30%). High relative humidity (85%) during growth tended to improve muscle structure and tenderness (68 and 72°C cooking temperature), regardless of environmental temperature. Breed‐treatment interactions for muscle structure score indicated that Poland China and Hampshire pigs differed in response to environment. Breed comparisons over all treatments revealed that muscle from Poland China pigs was less tender than muscle from Hampshire pigs when it was heated to 60°C. The data on tenderness suggest that the major environmental effects were exerted on the muscle constituents which are susceptible to high cooking temperatures (protein hardening range) whereas the breed differences were evident at low cooking temperatures (collagen shrinkage range).

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