The validity of a portable accelerometer for estimating energy expenditure in bicycle riding.

The purpose of the investigation was to determine the validity of a portable vertical accelerometer and a Large-Scale Integrated Motor Activity Monitor (LSI) for estimating energy expenditure in riding a bicycle at various velocities. Instrument placement was either at the knee or ankle. Energy consumption, i.e. oxygen consumption (VO2) was determined during bicycle rides after steady state metabolism was reached. Standard errors of estimate were used to express the accuracy of estimating VO2 from accelerometer or LSI recordings. The reliability of the vertical accelerometer was found to be satisfactory. The vertical accelerometer was also effective for estimating VO2 in bicycling (standard errors of estimate = 3.3 to 4.4 ml.kg-1.min-1). The accuracy of the LSI was not as good; the standard errors of estimate being = 5.9 to 8.5 ml.kg-1.min-1.

Characteristics and performance of male citizen cross-country ski racers.

Forty-three male citizen or recreational cross-country (X-C) ski racers (aged 31 +/- 4.4 years) were tested to determine their weight (BW) and percent body fat (BF), maximal oxygen uptake (VO2max), quadriceps (Quad), hamstrings (Ham) and upper body (UBS) isokinetic strength (60 degrees, 180 degrees, 240 degrees/s), and Quad endurance. In addition, skiers filled out a questionnaire to determine their skiing experience and to see what other activities they participated in. All these variables were run through a stepwise regression procedure to see which characteristics best predicted performance in a 10 km X-C ski race. The relatively high VO2max of 56.6 ml O2/kg/min and low BF of 10.1% indicate this group to be a very fit subset of the general population. All the skiers were active in other sports on a year-round basis. Of the variables studied, UBS, VO2max, and Quad strength were all significant determinants of 10 km race performance, yielding a multiple R of 0.78. Quad endurance, Ham strength, BW, BF, and experience did not significantly contribute toward the prediction of performance. It is felt that a proper training program for the citizen X-C skier should strive to maximize upper body strength as well as one's aerobic capacity.

Cardiovascular responses to military antishock trouser inflation during standing arm exercise.

Military antishock trousers (MAST) inflated to 50 mmHg were used with 12 healthy males (mean age 28 +/- 1 yr) to determine the effects of lower-body positive pressure on cardiac output (Q), stroke volume (SV), heart rate (HR), systolic blood pressure (SBP), diastolic blood pressure (DBP), mean arterial blood pressure (MABP), total peripheral resistance (TPR), and O2 uptake (VO2) during graded arm-cranking exercise. Subjects were studied while standing at rest and at 25, 50, and 75% of maximal arm-cranking VO2. At each level, rest or work was continued for 6 min with MAST inflated and for 6 min with MAST deflated. Order of inflation and deflation was alternated at each experimental rest or exercise level. Measurements were obtained during the last 2 min at each level. Repeated-measures analysis of variance revealed significant increases (P less than 0.001) in Q, SV, and MABP and a consistent decrease in HR with MAST inflation. There was no apparent change in Q/VO2 between inflated and control conditions. There was no effect of MAST inflation on VO2 or TPR. MAST inflation counteracts the gravitational effect of venous return in upright exercise, restoring central blood volume and thereby increasing Q and MABP from control. HR is decreased consequent to increased MABP through arterial baroreflexes. The associated decrease in TPR is not observed, being offset by the mechanical compression of leg vasculature with MAST inflation.