The energy cost of women walking and running in shoes and boots.
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Adult↗
Biomedical subjects
J J Knapik
Publications and source records attributed to J J Knapik.
Effects of virus infection on physical performance in man.
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Body Temperature↗
The energy cost and heart-rate response of trained and untrained subjects walking and running in shoes and boots.
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Adult↗
Isometric, isotonic, and isokinetic torque variations in four muscle groups through a range of joint motion.
The purpose of this investigation was to describe and examine variations in maximal torque produced by knee extension, knee flexion, elbow extension, and elbow flexion through a range of joint motion. Subjects were young, healthy men (n = 16) and women (n = 15). Torque was measured isometrically and isokinetically using a modified Cybex apparatus. Isotonic torque was calculated from a one-repetition maximum using a modified N-K device. Joint angles were monitored with an electrogoniometer. Torque-joint angle curves were constructed for both men and women for each muscle group. Isometric torque was highest, followed by isotonic and isokinetic torque. Torque declined with increasing isokinetic velocity. The angle of peak torque was found to be highly variable in individual subjects. Variations in torque curves were explained in terms of mechanical characteristics of the musculoskeletal system. Muscle group capability was generally found to be well matched to the mechanical requirements of the movement.
Adult↗
Isokinetic, isometric and isotonic strength relationships.
Relationships among isokinetic, isometric and isotonic strength measurements in knee and elbow extension and flexion were examined in 16 young, healthy men. Isokinetic and isometric torque measurements were obtained from modified Cybex II apparatus. Isokinetic torque values were obtained at velocities of 36 degrees/sec, 108 degrees/sec, and 180 degrees/sec. An electrogoniometer was used to monitor joint angle. A device similar to a Noland-Kuckhoff (NK) table was employed to determine maximal isotonic capabilities using a 1 repetition maximum procedure. Correlations among the 3 testing modes at joint angles of peak isometric torque were generally high (mean = 0.78, range = 0.97 to 0.47) for all 4 muscle groups. The amounts of common variance suggested that all 3 strength testing modes were measuring a similar phenomenon which could be termed maximal voluntary strength. Within a particular muscle group correlations decreased as isokinetic velocities and joint angles became more widely separated.
Adult↗
Effects of travel across time zones (jet-lag) on exercise capacity and performance.
Eighty-one healthy male soldiers, aged 18-34, were studied for 5 d before and 5 d after an eastward deployment across six time zones to determine the effects of translocation on exercise capacity and performance. Fatigue, weakness, headache, sleepiness, irritability, and other commonly reported symptoms occurred in the majority of subjects. Most, but not all, of the symptoms were diminished or absent by the fifth day following the translocation. Cardiorespiratory function and perception of effort during both submaximal and maximal treadmill exercise were unaffected. Isometric strength of the upper torso, legs, and trunk extensor muscles also was not changed. Dynamic strength and endurance of elbow flexors declined significantly. Dynamic knee extensor strength and endurance scores exhibited a progressive decrement prior to translocation and were inconsistent suggesting that the stress of repetitive testing outweighed any jet-lag effects on performance capacity. Performance times for a 270 m sprint were increased for the first 4 d following translocation as were times for a 2.8 km run on the second and third days and for a 110 m lift and carry on the third day after deployment. Times for a 6.5 m rope climb did not change. These findings indicate that certain symptoms and physiological capacities are affected as a result of multiple time zone translocation. However, the specific mechanisms involved, the factors influencing the magnitude of any physiological alterations, and the ultimate impact of these capacity changes on actual physical performance remain to be clarified.
Adaptation, Physiological↗
Height, weight, percent body fat, and indices of adiposity for young men and women entering the U.S. Army.
The purpose of this investigation was to describe the height (H), weight (W), and percent body fat (%BF) of young men and women (ages 17-35 years) entering the U.S. Army and to determine an index of adiposity that fit criteria described in the literature. H and W were measured with a digital scale and anthropometer, respectively. %BF was calculated from four skinfolds thickness. Men and women were both separated into four age categories. Very little difference in H was found with increasing age. W and %BF increased progressively with age in the males but no increase in either parameter was seen within the three youngest age groups of women. For males, W/H2 was found to be the most appropriate index of adiposity of those studied, having a correlation with %BF of 0.75 and a standard error of estimate of +/- 3.4 %BF. W/H1.5 was the most appropriate index for females, having a correlation with %BF of 0.69 and a standard error of estimate of +/- 3.2 %BF. It was suggested that these indices could be used to replace or supplement the current H-W charts used in the Army. A table for predicting %BF from these indices has been provided.
Adipose Tissue↗
Comparison of isokinetic measurements with test repetitions.
The purpose of this study was to examine changes in peak torque of the knee extensor muscles for a group of subjects. In each of three sessions, six maximal isokinetic contractions (trials) were elicited from 12 men and 4 women without isokinetic testing experience. No significant differences occurred over sessions and trials, but there was a significant interaction effect. Significant quadratic trends occurred in Sessions 1 and 3. In Session 1, the first trial was the highest; in Session 3, the first trial was the lowest. In Session 1, Trial 1 was significantly higher than Trial 3. No significant trend was found in Session 2. The results demonstrated that peak torque did not change when test sessions occurred two weeks apart. The pattern of peak torque values differed, however. If inexperienced subjects are tested in one session only, at least one maximal trial should be given before criterion scores are obtained.
Adult↗
Sparing effect of chronic high-altitude exposure on muscle glycogen utilization.
Substrate utilization during heavy [approximately 85% maximum O2 consumption (VO2max)] bicycle exercise was examined in eight low-altitude residents at sea level (SL) and after acute (2 h) and chronic (18 days) high-altitude (HA) exposure at 4,300 m. Mean VO2max was approximately 27% lower at acute HA than at SL and did not change significantly with continued HA exposure. Biopsies from the vastus lateralis muscle and venous blood samples were obtained before and after 30 min of exercise, whereas determinations of the respiratory exchange ratio (R) were made at 10-min intervals during each of the submaximal bouts. Resting levels of serum-free fatty acids at acute and chronic HA were, respectively, two and three times higher than SL but were unchanged with exercise. Exercise did not alter resting serum glycerol levels at SL or during acute HA, but during chronic HA resting glycerol levels were increased 11-fold. Although mean blood lactate concentrations following exercise at SL and acute HA were not significantly different, postexercise lactate concentrations were 87% lower after chronic HA. During exercise at SL and acute HA, muscle glycogen utilization and R were not different. At chronic HA, muscle glycogen utilization and R were 41 and 15% lower, respectively. These data suggest that after chronic HA exposure, increased mobilization and use of free fatty acids during exercise resulted in sparing of muscle glycogen.
Adaptation, Physiological↗
Isokinetic and isometric torque relationships in the human body.
To study the relationship between isokinetic and isometric torque, maximum voluntary contractions were elicited from 352 male volunteers. Knee extensors, knee flexors, elbow extensors, and elbow flexors were tested isometrically and at isokinetic velocities of 30 degrees/sec, 90 degrees/sec, and 180 degrees/sec on a modified Cybex II apparatus. Isokinetic torque declined with increasing velocity of contraction. Intercorrelations of the isometric and isokinetic torque showed a moderate to high relationship between these 2 modes of testing. A higher relationship was noted between the isometric tests and the low-velocity isokinetic tests and between isokinetic velocities that were closest together. The correlations decreased as the isokinetic velocities became more widely separated. These data suggest that the torque elicited at low-velocity isokinetic contractions can be predictive of the torque elicited during isometric contractions. Faster velocities are less related to isometric strength.
Adolescent↗
The influence of U.S. Army Basic Initial Entry Training on the muscular strength of men and women.
The influence of U.S. Army Basic Initial Entry Training on the maximum voluntary isometric strength (MVIS) and anthropometric parameters of men and women was investigated. Significant increases in weight and lean body mass (LBM) and decreases in percent body fat were found for both sexes during training. Significant increases in the MVIS of the upper torso (UT), leg extensors (LE), and trunk extensors (TE) were also found for both sexes. Females and males improved about the same amount on the LE (12.4% and 9.7%, respectively) but females improved significantly more than males on the UT (9.3% and 4.2%, respectively) and TE (15.9% and 8.1%, respectively). The greater gains in the females were presumably due to their lower initial strength levels and the consequently greater relative training stimulus. When strength was expressed relative to LBM, both sexes were able to exert similar amounts of strength on the LE and TE, suggesting that differences in strength between the sexes may primarily be a function of muscle mass.
Adolescent↗
The influence of physical fitness training on the manual material handling capability of women.
This study examined the influence of a generalized physical fitness training program on manual material handling (MMH) capability. Thirteen healthy women trained for 14 weeks, performing progressive resistance training three days per week and running with interval training two days per week. Subjects attended 85 +/- 6% of the sessions. Compared to values obtained before training, subjects increased the maximum mass they could lift from floor to knuckle height by 19% (68-81 kg, p < 0.001) and from floor to chest height by 16% (49-57 kg, p < 0.001). They improved by 17% their ability to lift 15 kg as many times as possible in 10 min(167-195 lifts, p < 0.001), while perception of effort (measured with the Borg Rating of Perceived Exertion) did not change. Total body mass did not change, but body fat mass was reduced by 9% (18.8-17.2 kg, p = 0.036) and fat-free mass increased by 6% (48.2-51.0 kg, p < 0.001). A short-term physical fitness program, conducted about 1 h per day, five days per week, can substantially improve women's MMH capability and provide favorable changes in body composition (increased fat-free mass and decreased body fat.
Adult↗
Preseason strength and flexibility imbalances associated with athletic injuries in female collegiate athletes.
One hundred thirty-eight female collegiate athletes, participating in eight weightbearing varsity sports, were administered preseason strength and flexibility tests and followed for injuries during their sports seasons. Strength was measured as the maximal isokinetic torque of the right and left knee flexors and knee extensors at 30 and 180 deg/sec. Flexibility was measured as the active range of motion of several lower body joints. An athletic trainer evaluated and recorded injuries occurring to the athletes in practice or competition. Forty percent of the women suffered one or more injuries. Athletes experienced more lower extremity injuries if they had: 1) a right knee flexor 15% stronger than the left knee flexor at 180 deg/sec; 2) a right hip extensor 15% more flexible than the left hip extensor; 3) a knee flexor/knee extensor ratio of less than 0.75 at 180 deg/sec. There was a trend for higher injury rates to be associated with knee flexor or hip extensor imbalances of 15% or more on either side of the body. These data demonstrate that specific strength and flexibility imbalances are associated with lower extremity injuries in female collegiate athletes.
Adolescent↗
Validity of self-assessed physical fitness.
This study compared self-ratings of components of physical fitness with objective measures of physical fitness. We made comparisons in two groups of male infantry soldiers (n = 96 and n = 276) and one group of older male military officers (n = 241). To obtain self-ratings of physical fitness, we asked subjects, "Compared to others of your age and sex, how would you rate your (a) endurance, (b) sprint speed, (c) strength, (d) flexibility?" Subjects responded to each of the four questions on a five-point scale. Self-ratings of endurance were systematically related to three measures of aerobic capacity, including VO2max, peak VO2, and two-mile run time (r = 0.29 to 0.53). Self-ratings of sprint speed showed only weak relationships to measures of anaerobic capacity assessed by the Wingate test, push-ups, and sit-ups (r = 0.10 to 0.17). Strength ratings were systematically related to measures of maximal strength (r = 0.28 to 0.53). Upper body strength measures were more closely associated with the self-ratings of strength than were measures of lower body strength. Responses to the flexibility question were systematically related to measures of hip/low back flexibility (r = 0.30 and 0.48) but not to other measures of flexibility. Apparently, physically active subjects can approximately classify their aerobic capacity, muscle strength, and some types of flexibility.
Age Factors↗
Cigarette smoking, physical fitness, and injuries in infantry soldiers.
Reliable data on the impact of physical training on light infantry units in terms of injuries and time loss are sparse. This study evaluated a light infantry unit (n = 181) prospectively and followed it throughout one year of infantry training and operations. Fifty-five percent of the soldiers (n = 101) experienced one or more injuries. Eighty-eight percent of the injuries were training-related conditions, which resulted in 1,103 days of limited duty. Lower extremity overuse injuries were the most common type of injury documented. Fractures accounted for the greatest number of days of limited duty. Risk factors for training-related injuries identified by this study were cigarette smoking, high percentage of body fat, extremely high or low body mass index, low endurance levels, and low muscular endurance levels (sit-ups). Logistic regression showed that cigarette smoking and low endurance levels were independent risk factors for training injuries. These data indicate that the incidence of training-related injuries in infantry units is high. A number of modifiable injury risk factors were identified, suggesting that many of these injuries may be preventable.
Adult↗