Submaximal Testing to Estimate Aerobic Capacity Using a Matrix C5x Stepmill.

The primary purpose of this study was to determine if the Matrix C5x stepmill's preprogrammed submaximal test is able to accurately predict maximal oxygen uptake. Sixteen participants completed a maximal treadmill test and a preprogrammed submaximal test on a Matrix C5x stepmill. Oxygen uptake was measured using a Cosmed K5 during both tests. Maximal oxygen uptake (VO2max) was calculated from submaximal data using a multi-stage calculation and compared against measured VO2max from the maximal test and estimated VO2max from the submaximal stepmill test. METs were also measured during the submaximal test and compared to the METs estimated by the stepmill and METs calculated using submaximal stepping equations. Measured VO2max (39.18 α 6.6 ml.kg-1.min-1) was significantly higher (p < 0.001) than estimated VO2max (28.06 α 3.2 ml.kg-1.min-1) and calculated VO2max (35.58 α 8.0 ml.kg-1.min-1). Measured METs were significantly (p = 0.04) higher than estimated METs in all stages, and higher than calculated METs in stage 1 of the submaximal test. The C5x did not provide accurate estimations of METs or maximal oxygen uptake. Calculating maximal oxygen uptake from submaximal stepmill data may provide an alternative, although development of a new equation may be warranted.

Peak Loads Associated With High-Impact Physical Activities in Children.

Physical activities involving impact loading are important for improving bone strength and mineral density in children. There is little research quantifying impact loads associated with various high-impact activities. PURPOSE: Examine the magnitude of peak ground reaction forces (pGRF) across different jumping activities in children. METHODS: Eight children between 8 and 12 years (9.63 [1.49] y; 1.42 [0.08] m; 33.69 [4.81] kg), performed 5 trials of a broad jump, countermovement jump, jumping jack, leap jump, and drop jump on a force plate. The pGRF were determined during the landing phase of each activity and expressed in units of body weight (BW). A repeated-measures analysis of variance was employed to assess differences in pGRF across activities. RESULTS: Drop jump exhibited the greatest pGRF (3.09 [0.46] BW) in comparison with the vertical jumping jack (2.56 [0.21] BW; P < .001) and countermovement jump (2.45 [0.22] BW; P = .001), as well as the horizontal broad jump (2.25 [0.2] BW; P = .003), and leap jump (2.01 [0.1] BW; P = .002). CONCLUSION: Peak loads between 2 and 3.1 BW were exhibited across each jump activity, which is moderate compared with magnitudes in most jump interventions seeking to improve bone health. All conditions except drop jump exhibited loading <3 BW, suggesting these activities may not produce sufficient loads to improve bone outcomes.

Top 10 research questions related to physical activity and bone health in children and adolescents.

Evidence strongly supports a positive, causal effect of physical activity on bone strength and suggests long-term benefits of childhood physical activity to the prevention of osteoporosis. The contribution of healthy bone development in youth is likely to be as important to fracture prevention as the amount of late adulthood bone loss. Families, schools (particularly physical education), and communities are key settings for health promotion focused on bone-enhancing physical activity. However, little research has explored the topic of health promotion and physical education as they pertain to bone health, so best practices are not known. Based on our understanding of the literature, we present the top 10 research questions in health promotion and physical education that should be answered to advance bone-enhancing physical activity in children and adolescents.

Anterior glenohumeral laxity and stiffness after a shoulder-strengthening program in collegiate cheerleaders.

CONTEXT: Approximately 62% of all cheerleaders sustain some type of orthopaedic injury during their cheerleading careers. Furthermore, the occurrence of such injuries has led to inquiry regarding optimal prevention techniques. One possible cause of these injuries may be related to inadequate conditioning in cheerleaders. OBJECTIVE: To determine whether a strength and conditioning program produces quantifiable improvements in anterior glenohumeral (GH) laxity and stiffness. DESIGN: Descriptive laboratory study. SETTING: University laboratory. PATIENTS OR OTHER PARTICIPANTS: A sample of 41 collegiate cheerleaders (24 experimental and 17 control participants) volunteered. No participants had a recent history (in the past 6 months) of upper extremity injury or any history of upper extremity surgery. INTERVENTION(S): The experimental group completed a 6-week strength and conditioning program between the pretest and posttest measurements; the control group did not perform any strength training between tests. MAIN OUTCOME MEASURE(S): We measured anterior GH laxity and stiffness with an instrumented arthrometer. We conducted a group × time analysis of variance with repeated measures on time (P < .05) to determine differences between groups. RESULTS: A significant interaction was demonstrated, with the control group having more anterior GH laxity at the posttest session than the strengthening group (P = .03, partial η2 = 0.11). However, no main effect for time (P = .92) or group (P = .97) was observed. In another significant interaction, the control group had less anterior GH stiffness at the posttest session than the strengthening group (P = .03, partial η2 = 0.12). Main effects for time (P = .02) and group (P = .004) were also significant. CONCLUSIONS: Cheerleaders who participate in a shoulder-strengthening program developed less anterior GH laxity and more stiffness than cheerleaders in the control group.

Event standardization of sit-to-stand movements.

BACKGROUND AND PURPOSE: Unlike gait analysis, no commonly accepted method for studying sit-to-stand (STS) movements exists. Most previous studies describing STS events used various methods to identify movement events while restricting sitting positions and movements. The present study observed natural rising from a sitting position using a simple method for measuring this common task. The purposes of this study were to compare commonly performed STS movements and to propose a standard system for defining identifiable sequential events. SUBJECTS AND METHODS: Ground reaction forces of 100 adults who were healthy (50 male, 50 female) were recorded using a force platform as each participant performed 4 methods of rising from sitting on a standard chair. The 4 STS conditions were: with arms free, with hands on knees, using armrests, and with arms crossed. RESULTS: For each subject, 11 recorded events from the vertical, fore-aft, and lateral dimensions were identified for all arm-use conditions. The only significant and clinically relevant force difference among arm-use conditions was that the armrests condition produced less average force than the other 3 conditions during the seat-off and vertical peak force events. Among average event times, the armrests condition showed significantly longer time to the vertical peak force event than the other conditions. DISCUSSION AND CONCLUSION: Because these events occurred invariably in sequential order for every individual for all arm-use conditions in a relatively large sample of observations during natural STS movements, this method may be useful for establishing a standard method to assess and compare patient functionality and allow comparisons among STS research studies.

Physical fitness profile of Army ROTC cadets.

One role of Army Reserved Officer's Training Corps (ROTC) programs is to physically prepare cadets for the demands of a military career. Cadets participate in physical training 3 days per week as part of their military science curriculum. Limited research has been conducted on the fitness level of ROTC cadets; therefore, the purpose of this study was to profile the physical fitness status of a cadre of ROTC cadets. Forty-three cadets (30 men and 13 women) performed Army Physical Fitness Test (APFT) assessments (2-mile run, 2-minute maximum push-ups and sit-ups) and clinical assessments of fitness (Bruce protocol Vo(2)max, underwater weighing, and 1 repetition maximum [1RM] bench press tests). Mean +/- standard deviations were calculated to provide the physical fitness profile for each parameter. Male cadets (21 +/- 2.2 years; height 177.4 +/- 6.6 cm; mass 79.2 +/- 9.4 kg) scored 49.6 +/- 6.1 ml.kg(-1).min(-1) for Vo(2)max, 14.8 +/- 4.2% fat, 86.5 +/- 24.9 kg 1RM bench press, 2-mile run of 13.97 +/- 1.4 minutes, 70.5 +/- 12.8 sit-ups, and 60.2 +/- 13.2 push-ups. Female cadets (20 +/- 2.4 years; height 165.1 +/- 8.0 cm; mass 63.5 +/- 10.0 kg) scored 40.8 +/- 3.9 ml.kg(-1).min(-1) for Vo(2) max, 23.9 +/- 3.8% fat, 35.3 +/- 8.2 kg 1RM bench press, 2-mile run of 17.0 +/- 1.6 minutes, 65.0 +/- 12.9 sit-ups, and 33.3 +/- 11.2 push-ups. The mean scores were above the 83rd percentile on all APFT items and average (percent fat) to above average (Vo(2)max and men's bench press scores) when compared with peer-age and sex-corrected norms. Only the women's bench press score was below average. With the exception of the women's bench press, these ROTC cadets possessed average to above average levels of fitness.

Physiologic profile of the fitness status of collegiate cheerleaders.

Cheerleading, traditionally considered a nonathletic activity, has evolved into a competitive sport requiring high levels of fitness. Despite the trend of cheerleaders performing increasingly difficult and athletic skills, very little is known about their fitness levels. The purpose of this study was to provide a physiological profile of the fitness status of a squad of collegiate cheerleaders. Eighteen cheerleaders (11 men and 7 women) participated in this study. Each subject completed a Bruce protocol maximal treadmill test, underwater weighing, 1 repetition maximum bench press, sit-and-reach test, push-ups, curl-ups, and isokinetic strength testing. The mean and SD were calculated to provide the physical fitness profile for each parameter. A comparison to normative data demonstrated that cheerleaders have a high level of fitness and scores similar to other collegiate athletes.

Ratings of perceived exertion and muscle activity during the bench press exercise in recreational and novice lifters.

This study examined ratings of perceived exertion (RPE) and electromyography (EMG) during resistance exercise in recreational and novice lifters. Fourteen novice (age = 21.5 +/- 1.5 years) and 14 recreationally trained (age = 21.9 +/- 2.2 years) women volunteered to perform the bench press exercise at 60 and 80% of their 1 repetition maximum (1RM). RPE and EMG were measured during both intensities. Statistical analyses revealed that active muscle RPE increased as resistance exercise intensity increased from 60% 1RM to 80% 1RM (12.32 +/- 1.81 vs. 15.14 +/- 1.74). Integrated EMG also increased as resistance exercise intensity increased from 60% 1RM to 80% 1RM (in the pectoralis major; 98.62 +/- 17.54 vs. 127.98 +/- 29.02). No significant differences in RPE or EMG were found between novice and recreational lifters. These results indicate that RPE is related to the relative exercise intensity lifted as well as muscle activity during resistance exercise for both recreational and novice lifters. These results support the use of RPE as a method of resistance exercise intensity estimation for both types of lifters.

Effect of exercise-induced changes in residual lung volume on the determination of body composition.

The transient increase in residual lung volume (RV) as a result of exercise has been well documented. An accurate assessment of exercise-induced RV would be important when hydrostatic weighing (HW) is performed after exercise. The purpose of this study was to determine whether accurate HW measures could be performed after exercise when changes in RV are measured. Subjects (n = 32) performed pulmonary function (vital capacity [VC]-estimated RV), oxygen dilution-determined RV, and HW measures before and after either a maximal treadmill test (n = 16) or seated rest (n = 16). Two-way analysis of variance (p