Jon Linderman

The Fischer 344/NNiaHSd X Brown Norway/BiNia is a better model of sarcopenia than the Fischer 344/NNiaHSd: a comparative analysis of muscle mass and contractile properties in aging male rat models.

Sarcopenia, characterized by profound muscle atrophy and the loss of contractile function, contributes significantly to the development of frailty and functional impairment in older age. Although present in aging humans, rat models have failed to clearly demonstrate a similar degree of this age-associated loss of muscle mass and function. This investigation compared two models of rats raised specifically for aging studies, the Fischer 344/NNiaHSd (F344/N) and the Fischer 344/NNiaHSd X Brown Norway/BiNia (F344/NXBN), and sought to determine which model provides the most accurate representation of human sarcopenia. We found that aging had no effect on F344/N muscle mass or contractile function in the extensor digitorum longus (EDL) and soleus (SOL). Conversely, in the F344/NXBN model, aging was found to decrease EDL and SOL mass and contractile function. These changes were sufficient to satisfy the proposed criteria for the diagnosis of human sarcopenia based upon muscle mass and contractile function. Results indicate that the F344/NXBN provides a better model of the alterations seen in aging human muscle than the F344/N rat model.

ULTRA ENDURANCE CYCLING: A FIELD STUDY OF HUMAN PERFORMANCE DURING A 12 HOUR MOUNTAIN BIKE RACE

ULTRA-ENDURANCE CYCLING: A FIELD STUDY OF HUMAN PERFORMANCE DURING A 12HOUR MOUTAIN BIKE RACE. Jon Linderman, Tim Demchak, Julie Dallas, Janet Buckworth. JEPonline. 2003;6(3):10-19. To investigate changes in physiological and psychological function during ultraendurance events, 6 healthy cyclists (31.5±1.6 years) were studied during a 12-hour mountain bike race. Subjects covered 119-170 km, at average velocities of 11-14 km/hour. During the first two hours of the event heart rates averaged 155-157 beats/min, declined significantly during the third hour (142±14 beats/min; p<0.05), and was largely unchanged throughout the remaining nine hours of the race. Subjects consumed 15503300 Kcals during the event with an average of 662±76 g of carbohydrate. Although subjects consumed 45006400 mL of fluid during the race, hydration status, assessed from changes in body weight, indicated a dehydration indirectly quantified as a ~4% decrease in body weight preto post race (2.3±1.4 kg; p<0.05). Using the 10-point Borg Scale subjects rating of perceived exertion (RPE) increased hourly from 4.0±1.3 after the first hour of competition to 9.2±1.0 during the twelfth hour of competition (p<0.05). Profile of moods state (POMS) administered during the event revealed declines in vigor preto post-race (11.5±2.3 vs. 3.8±1.7; p<0.05), with concomitant increases in fatigue scores (5.3±2.8 vs. 19.3±0.5; p<0.05). Results of the present investigation suggest greater declines in mental than physiological function during prolonged offroad cycling competition.

GENDER DIFFERENCES IN CARDIOVASCULAR RESPONSE TO ISOMETRIC EXERCISE IN THE SEATED AND SUPINE POSITIONS 999

ABSTRACT Donald R Melrose. Gender Differences In Cardiovascular Response To Isometric Exercise In The Seated And Supine Positions. JEP online . 2005;8(4):29-35. The purpose of this study was to 1) determine if the cardiovascular responses to isometric exercise differ between genders, and 2) determine if posture affects cardiovascular responses to isometric n women and 15 men (age 22.6±4.2 yrs) performed two randomized (seated or supine) maximal IHG trials at 40 %MVC one week apart. Blood pressure (BP) and heart rate (HR) measurements were collected at rest (RT), the first minute of exercise (M1), prior to failure (PF), and at 30 s of recovery following failure (RC). Mean arterial pressure (MAP), pulse pressure (PP), and rate pressure product (RPP) were calculated from BP and HR data. Analyses showed significant time by gender interactions for diastolic blood pressure (DBP) and MAP. Males had significantly higher DBP than females at M1 (105.46±14.97 vs. 92.59±13.14 mmHg), PF (122.46±11.23 vs. 109.50±13.72 mmHg) and RC (85.83±4.11 vs. 73.46 ± 8.35 mmHg) and higher MAP measurements than females at M1 (120.32 ± 13.76 vs. 105.43 ± 13.76 mmHg), PF (136.44 ± 8.65 vs. 24.31 ±13.34 mmHg), and RC (100.44 ±8.21 vs. 87.67 ±8.26 mmHg). DBP, MAP, and HR were significantly higher in the seated position than in the supine position for both genders. It was concluded that 1) men significantly increase MAP and DBP upon initiation of submaximal IHG exercise through recovery regardless of posture, 2) women have significantly lower blood pressure measurements than men during submaximal IHG exercise regardless of posture, and 3) posture has a significant affect on cardiovascular response during submaximal IHG exercise.

Body mass index associations between mother and offspring from birth to age 18: the Fels Longitudinal Study

Parental obesity is a known determinant of childhood obesity. Previous research has shown a strong maternal influence on body mass index (BMI) during infancy and early childhood.