The association of moderate-to-vigorous and light-intensity physical activity on static balance in middle-aged and older-aged adults.

BACKGROUND: Falls are the leading cause of injury among adults ≥ 65 years of age. Participation in physical activity (PA) is associated with improved balance, though it is impact in the middle-age population is not well understood. AIM: The purpose of the current study was to examine the influence of PA intensity on static balance in middle-aged and older aged individuals. METHODS: Included were middle-aged adults (40-64 years) and older adults (≥ 65 years) from the 2003-2004 years of the National Health and Nutrition Evaluation Survey. Light physical activity (LPA) and moderate-vigorous physical activity (MVPA) were collected via accelerometer and static balance via the Romberg Test of Standing Balance. RESULTS: No significant odds ratio relationship was found between MVPA or LPA and having good static balance in the middle-aged population; 1.04 (95% CI 0.95, 1.13) p = 0.427 and 1.05 (95% CI 0.97, 1.14) p = 0.182, respectively. Whereas, in older adults, every 60-min increase in LPA was significantly associated with 28% higher odds of good balance (95% CI 1.15, 1.41; p < 0.001), and every 10-min increase in MVPA with 25% higher odds of good balance (95% CI 1.08, 1.45; p = 0.006). DISCUSSION: LPA and MVPA were not associated with good static balance in middle-aged adults, but in older adults LPA was significantly associated with good static balance. CONCLUSION: A significant relationship is found between age and fall risk, which is a major concern in the aging population.

Influence of Body Mass on Fitness Performance in Naval Special Warfare Operators.

ABSTRACT: Wood, DE and Swain, DP. Influence of body mass on fitness performance in Naval Special Warfare operators. J Strength Cond Res 35(11): 3120-3127, 2021-U.S. Naval Special Operations Forces have performed some of the U.S. Military's most rigorous missions. The Human Performance Program (HPP) developed a physical performance testing battery to assess and monitor physical fitness. Testing bias relative to body mass has been noted in the past literature, including military physical fitness tests. This retrospective study looked to determine whether there is body mass bias in the HPP fitness assessment and whether an optimum body mass for each fitness test could be determined. Data from 333 subjects (age: 28.4 ± 5.0 years; height: 178.4 ± 6.2 cm; mass: 86.0 ± 9.2 kg) were analyzed to compare body mass with performance on the 8 tests: standing long jump, Pro-Agility test, weighted pull-up, body weight bench press, 1 repetition maximum (1RM) deadlift, 274-m shuttle run, 4.83-km run, and 800-m swim. Linear regression analysis was used to analyze the relationship of body mass to performance; a second-degree polynomial was used to determine best-fit curves for each of the physical fitness tests; analysis of variance was used to examine differences in performance between body mass groups. Significantly better performance for lighter subjects was found in the Pro-Agility test, weighted pull-up, body weight bench press, 274-m shuttle run, and 4.83-km run. Heavier subjects performed better in the 1RM deadlift. Second-degree polynomial regression revealed optimum body mass for the Pro-Agility test, 274-m shuttle run, and 4.83-km run to be 7-16 kg heavier than the lowest body mass. These findings could help professionals better assess and train operators of varying body size.

The Physical Parameters of Tactical Climbing and Performance Characteristics of Naval Special Warfare Operators.

ABSTRACT: Wood, DE and Swain, DP. The physical parameters of tactical climbing and performance characteristics of naval special warfare operators. J Strength Cond Res 35(4): 949-954, 2021-Vertical elevation may be critical for advantage to Special Operation Forces and require strength, power, endurance, and technique. This study sought to (a) study differences in physical capacities of Naval Special Warfare lead climbers from nonlead climbers, (b) compare anthropometrics of lead climbers from nonlead climbers, and (c) catalogue the types and weights of the various climbing systems to assess total system weight to the lead climber's body mass. Climbing surveys were collected and retrospective physical capacity data from 15 SEa, Air and Land lead climbers (age: 31.2 ± 5.1 years; height: 181.4 ± 6.4 cm; mass: 89.4 ± 10.0 kg; body fat: 14.1 ± 3.7%) were compared against previously reported data of 305 nonlead climbers (age: 28.8 ± 5.2 years; height: 177.6 ± 12.0 cm; mass: 85.8 ± 9.7 kg; body fat: 17.3 ± 4.7%). Lead climbers had significantly less body fat percentage (p = 0.017). Lead climbers also performed significantly better on the pro-agility test (p = 0.017) and deadlift (p = 0.002). The total mass reported for the climbing equipment for each tactical scenario was up to 4.9 kg for urban climbing, up to 13.7 kg for alpine climbing, and up to 8.0 kg for maritime climbing. With a typical combat load of 21.4 kg, adding an alpine climbing load exceeds one-third of the lead climbers' own body mass. Strength and conditioning programming for this population should take into consideration the total system weight for testing and training purposes and should also consider climbing-specific strength testing and training to optimize climbing capability.

Ammonia Inhalation Does Not Increase Deadlift 1-Repetition Maximum in College-Aged Male and Female Weight Lifters.

Vigil, JN, Sabatini, PL, Hill, LC, Swain, DP, and Branch, JD. Ammonia inhalation does not increase deadlift 1-repetition maximum in college-aged male and female weight lifters. J Strength Cond Res 32(12): 3392-3397, 2018-Ammonia inhalant use by powerlifters and weight lifters is a prevalent practice with little research support for improved performance. The purpose of this study was to investigate the effects of ammonia as a stimulant on athletic performance during a deadlift 1-repetition maximum (1RM) absolute strength test. Subjects (men: n = 10, mean ± SD age = 21 ± 1 year, mass = 72.5 ± 6.8 kg; and women: n = 10, age = 22 ± 5 years, mass = 66.2 ± 8.1 kg) were required to have at least 2 years of resistance training experience while lacking a history of asthma, lightheadedness, fainting, anaphylaxis, sickle cell traits, and other respiratory disorders. After a baseline 1RM test, subjects were paired by 1RM performance and gender, then randomly assigned in a counterbalanced treatment order to control (water) or ammonia trials after a minimum 72-hour recovery period for another 1RM test involving attempts at 100.0, 102.5, 105.0, and 107.5% of the established 1RM value. Testing was then repeated after the minimum rest period for the remaining trial. Results revealed the expected gender main effect for absolute deadlift 1RM (93.0 ± 29.5 [women]; 152.0 ± 29.5 kg [men]; p < 0.001), but no trial main effect (p = 0.874) or gender by trial interaction effect (baseline = 93.0 ± 15.3, 151.8 ± 42.3 kg; water = 92.0 ± 12.5, 150.9 ± 37.8 kg; ammonia = 92.5 ± 16.4, 153.4 ± 37.9 kg) for women and men, respectively (p = 0.559). Within the limitations of this study, there is no support for the practice of ammonia inhalation to improve deadlift 1RM in training or competition.

Impact Forces of Walking and Running at the Same Intensity.

Moderate-intensity walking (horizontal, WH), vigorous-intensity walking (incline, WI), and vigorous-intensity running (horizontal, R) were compared. The hypothesis is that running creates greater loading forces than walking even at the same aerobic intensity. Young adults (10 M and 10 F; age, 22.8 ± 0.5 years) performed 3 exercise trials in a counter-balanced order: walking 5.5 kph at 0% grade (WH); walking 5.5 kph at 11% (WI); and running at 8.0 kph at 0% (R). Oxygen consumption (V[Combining Dot Above]O2), step frequency, peak vertical ground reaction force (VGRF), and vertical force loading rate were recorded during the last 5 minutes of each trial. Results are mean ± SE. Net V[Combining Dot Above]O2 during WH (10.5 ± 0.3 ml·min·kg) was significantly less than WI (26.3 ± 0.3) and R (25.1 ± 0.7 ml·min·kg). Step frequency was significantly greater during R (163 ± 1.5 steps per minute) than both walking conditions (WH, 128 ± 1.0 steps per minute; WI, 126 ± 1.2 steps per minute). Peak VGRF was significantly greater during running (844 ± 47 N) than both walking conditions (WH, 581 ± 27 N; WI, 565 ± 28 N). Force loading rate was significantly greater with R (8,214 ± 26 N·s) than WH (6,497 ± 15 N·s ) and WI (5,699 ± 16 N·s ), with WH > WI. Vigorous-intensity walking produced no greater loading forces than moderate-intensity walking. However, running at a vigorous intensity produced substantially greater loading forces than walking of the same intensity. These findings suggest that vigorous aerobic exercise may be performed without elevated orthopedic stress, depending on the mode prescribed.

Effect of added mass on treadmill performance and pulmonary function.

Military personnel engage in strenuous physical activity and load carriage. This study evaluated the role of body mass and of added mass on aerobic performance (uphill treadmill exercise) and pulmonary function. Performance on a traditional unloaded run test (4.8 km) was compared with performance on loaded tasks. Subjects performed an outdoor 4.8-km run and 4 maximal treadmill tests wearing loads of 0, 10, 20, and 30 kg. Subjects' pulmonary function (forced expired volume in 1 second [FEV1], forced vital capacity [FVC], and maximal voluntary ventilation [MVV]) was tested with each load, and peak values of heart rate, oxygen consumption ((Equation is included in full-text article.)), ventilation (VE), and respiratory exchange ratio (RER) were measured during each treadmill test. Performance on the 4.8-km run was correlated with treadmill performance, measured as time to exhaustion (TTE), with the strength of the correlation decreasing with load (r = 0.87 for 0 kg to 0.76 for 30 kg). Body mass was not correlated with TTE, other than among men with the 30-kg load (r = 0.48). During treadmill exercise, all peak responses other than RER decreased with load. Pulmonary function measures (FEV1, FVC, and MVV) decreased with load. Body mass was poorly correlated with treadmill performance, but added mass decreased performance. The decreased performance may be in part because of decreased pulmonary function. Unloaded 4.8-km run performance was correlated to unloaded uphill treadmill performance, but less so as load increased. Therefore, traditional run tests may not be an effective means of evaluating aerobic performance for military field operations.

Autonomic response to tactical pistol performance measured by heart rate variability.

This study evaluated changes in autonomic tone during a tactical pistol competition. At rest and during a match, heart rate variability (HRV) was examined in 28 healthy subjects. Heart rate variability time-domain variables (including interbeat interval [IBI]) and frequency-domain variables (low frequency [LF], high frequency [HF], total power [TP]) measured during shooting were subtracted from those measured during rest to produce Δs. The shooting task involved several, rapid tactical maneuvers. Raw time to completion and inaccurate shots (points down [PDs]) were recorded and combined to form a match score where lower values indicated superior shooting performance. Mean (±SD) raw time was 135.9 ± 34.1 seconds, PDs were 78 ± 34, and match score was 175.3 ± 39.8. Shooting decreased IBI (i.e., increased heart rate) and LF. ΔLF, ΔHF, and ΔTP were independent of ΔIBI. Raw time was significantly (p ≤ 0.05) correlated to shooting IBI (r = 0.404) and ΔIBI (r = -0.426). Points down were significantly correlated to ΔTP (r = 0.416) and ΔLF (r = 0.376). Match score was significantly correlated to ΔIBI (r = -0.458), ΔHF (r = 0.467), ΔLF (r = 0.377), and ΔTP (r = 0.451). In conclusion, individuals with a greater decrease in IBI (and thus heart rate) performed better by accomplishing the match faster. Individuals with less change in stress-related HRV measures (LF, HF, and TP) performed better through improved accuracy. Thus, HRV-derived sympathetic response is significantly related to shooting performance and should be used to assess marksmanship effectiveness under duress.

Effect of intensity of aerobic training on insulin sensitivity/resistance in recreationally active adults.

Previous research demonstrates that moderate-intensity aerobic exercise improves insulin effectiveness. Whether higher exercise intensities improve insulin action more so is unclear. The purpose of this study was to evaluate the effect of various levels of aerobic intensity on insulin action in young adult men and women. Forty-five healthy subjects (22.2 ± 3.9 years; 169 ± 9 cm; 74.5 ± 17.8 kg) were matched for age, gender, and VO2max and randomly assigned to moderate-intensity (50% heart rate reserve [HRR]), vigorous-intensity (75% HRR), maximal-intensity intervals (95/50% HRR) or a non-exercising control group. Subjects completed a 6-week training protocol on a stationary bicycle ergometer. Weekly duration and frequency of training varied to ensure equivalent energy expenditure across groups. The homeostasis model assessment (HOMA) and quantitative insulin sensitivity check index (QUICKI) were used to assess insulin effectiveness. Significant increases occurred after training in VO2max in the vigorous-intensity(15.4%) and maximal-intensity(14.2%) groups (p < 0.01) but not the moderate-intensity or control group. There were no significant changes in insulin effectiveness in any exercise group. Training intensity did not significantly affect insulin effectiveness in a young adult population as assessed by HOMA or QUICKI; it did, however, significantly affect VO2max.

Effect of training with and without a load on military fitness tests and marksmanship.

The purpose of this study was to determine whether military-style training performed while carrying a weighted vest and backpack (Load condition) resulted in superior training adaptations (specifically, changes in military fitness and marksmanship) than did more conventional training (No-Load condition). A total of 33 college-aged men and women (16 Load, 17 No-Load) completed all testing and 9 weeks of training (1 h·d, 4 d·wk). No-Load training consisted of military calisthenics, sprints, agility drills, and running. Load training was similar except that running was replaced with stair climbing, and Load increased across the 9 weeks to 20 kg for women and 30 kg for men. Pretraining and posttraining, all subjects performed an uphill treadmill test with full load to determine peak oxygen consumption (VO(2)peak), the marine physical fitness test (PFT) and combat fitness test (CFT) without load, other fitness tests, and an indoor marksmanship test using a laser-fitted carbine. The marksmanship test was performed with full load and done before and immediately after a 200-m shuttle run performed in 60 seconds. Both groups significantly improved their VO(2)peak, PFT, and CFT scores by similar amounts. Pretraining, shooting score decreased significantly after the 200-m run and then rapidly recovered, with no difference between groups. A similar, but nonsignificant, pattern in shooting scores was seen in both groups posttraining. In conclusion, loaded training did not produce measurable advantages compared with unloaded training in this population. A strenuous anaerobic challenge caused a temporary reduction in marksmanship.

Effects of training on physical performance wearing personal protective equipment.

We evaluated the effects of wearing a weighted vest during 6 weeks of military-style training. Forty-three subjects were randomly assigned to a control group or a vest group (carrying 4-5 kg for 2 weeks, and 8-10 kg for 4 weeks), with 37 completing the study (17 vest, 20 control). Both groups performed stair climbing in addition to standard Marine Corps training for 1 hour, four times per week. Pre- and post-tests were performed while wearing military personal protective equipment, with the exception of the Marine Physical Readiness Test (PRT). Both groups significantly improved PRT scores (8.4% 3-mile run, 28-38% calisthenics) and an agility drill (4.4%). Significant improvements in uphill treadmill performance (6.8% vest, 3.0% control) and maximal oxygen consumption (10.7% vest, 6.8% control) were approximately twice as much in the vest versus control group, although these differences did not reach significance (p = 0.16 and 0.13, respectively).

Aerobic Recovery after Radical Prostatectomy: A Case Study.

PURPOSE: This case study examined the recovery after radical prostatectomy (RP) of an endurance-trained 65-yr-old man. METHODS: A maximal incremental exercise test and a 1-h steady-state test were performed just before and 3 months after robotic RP to determine maximal oxygen consumption (V˙O2max) and other cardiorespiratory variables. The patient recorded his training as he prepared for an endurance event that was to occur 3 months after RP, the Norwegian Foot March, a 30-km road march carrying 11.4 kg. RESULTS: In the month before RP, the patient performed 2 to 3 h of vigorous-intensity aerobic exercise per week, fast walking carrying an 11.4-kg pack, with the longest individual session being a 16-km road march. Just before surgery, V˙O2max was 36.7 mL·min·kg, HR during 30 min at 7.2 km·h and 0% grade was 77% of HR reserve (HRR), and during 30 min at 5.3 km·h and 10% grade was 92% HRR. On postsurgery day 44, he did a 19-km road march carrying 11.4 kg, exceeding the training level of the month presurgery. Three months postsurgery, V˙O2max was 42.7 mL·min·kg, and HR during the flat and uphill 30-min sessions at the same absolute intensity as presurgery were 70% and 83% HRR, respectively. He completed the Norwegian Foot March 93 d postsurgery in 4:24:37, with an average HR of 72% HRR. CONCLUSIONS: This case study demonstrates that an aerobically trained prostate cancer patient can return to high-level aerobic training in as little as 7 wk post-RP, and even exceed presurgery fitness. This finding has implications for prognosis given the beneficial effect of vigorous-intensity exercise on prostate cancer progression.

Effect of intensity of aerobic training on VO2max.

PURPOSE: To determine whether various intensities of aerobic training differentially affect aerobic capacity as well as resting HR and resting blood pressure (BP). METHODS: Sixty-one health young adult subjects were matched for sex and VO2max and were randomly assigned to a moderate- (50% VO2 reserve (VO2R), vigorous (75% VO2R), near-maximal-intensity (95% VO2R), or a nonexercising control group. Intensity during exercise was controlled by having the subjects maintain target HR based on HR reserve. Exercise volume (and thus energy expenditure) was controlled across the three training groups by varying duration and frequency. Fifty-five subjects completed a 6-wk training protocol on a stationary bicycle ergometer and pre- and posttesting. During the final 4 wk, the moderate-intensity group exercised for 60 min, 4 d.wk the vigorous-intensity group exercised for 40 min, 4 d.wk and the near-maximal-intensity group exercised 3 d.wk performing 5 min at 75% VO2R followed by five intervals of 5 min at 95% VO2R and 5 min at 50% VO2R. RESULTS: VO2max significantly increased in all exercising groups by 7.2, 4.8, and 3.4 mL.min.kg in the near-maximal-, the vigorous-, and the moderate-intensity groups, respectively. Percent increases in the near-maximal- (20.6%), the vigorous- (14.3%), and the moderate-intensity (10.0%) groups were all significantly different from each other (P < 0.05). There were no significant changes in resting HR and BP in any group. CONCLUSION: When volume of exercise is controlled, higher intensities of exercise are more effective for improving VO2max than lower intensities of exercise in healthy, young adults.

Comparison of cardioprotective benefits of vigorous versus moderate intensity aerobic exercise.

Aerobic fitness, not merely physical activity, is associated with a reduced risk of cardiovascular disease. Vigorous intensity exercise has been shown to increase aerobic fitness more effectively than moderate intensity exercise, suggesting that the former may confer greater cardioprotective benefits. An electronic search of published studies using PubMed was conducted for 2 types of investigations, epidemiologic studies that evaluated the benefits of physical activity of varying intensity levels and clinical trials that trained individuals at different intensities of exercise while controlling for the total energy expenditure. A secondary search was conducted using the references from these studies. The epidemiologic studies consistently found a greater reduction in risk of cardiovascular disease with vigorous (typically > or =6 METs) than with moderate intensity physical activity and reported more favorable risk profiles for individuals engaged in vigorous, as opposed to moderate, intensity physical activity. Clinical trials generally reported greater improvements after vigorous (typically > or =60% aerobic capacity) compared with moderate intensity exercise for diastolic blood pressure, glucose control, and aerobic capacity, but reported no intensity effect on improvements in systolic blood pressure, lipid profile, or body fat loss. In conclusion, if the total energy expenditure of exercise is held constant, exercise performed at a vigorous intensity appears to convey greater cardioprotective benefits than exercise of a moderate intensity.

Change in cutaneous perfusion following 10 weeks of aerobic training in Type 2 diabetes.

A small, but positive, association between aerobic training status or prior maximal exercise and enhanced dorsal foot skin perfusion in active individuals with Type 2 diabetes has been shown. This study, therefore, was designed to examine whether an aerobic training intervention would positively affect cutaneous perfusion in sedentary Type 2 diabetic individuals as well. Nine sedentary participants with Type 2 diabetes (DS) and 10 obese nondiabetic controls (CS) were studied. Prior to the initiation of aerobic training, dorsal foot cutaneous perfusion was measured noninvasively by continuous laser Doppler assessment at baseline and during localized heating to 44 degrees C. These measurements were repeated 48-72 h following 10 weeks of moderate aerobic training performed 3 days per week. Interstitial nitric oxide (NO) levels were measured concurrently in the contralateral foot dorsum. Aerobic training did not significantly enhance baseline skin perfusion, nor were interstitial NO levels different under any condition. At baseline, groups differed only in glycated hemoglobin (HbA1c), fasting serum glucose, HDL-cholesterol, and insulin resistance. At rest, cutaneous perfusion during local heating to 44 degrees C was significantly lower in DS before training, but did not differ significantly from CS afterward. Neither group, however, experienced significant increases in dorsal foot perfusion during local responsiveness to heating to 44 degrees C following 10 weeks of moderate aerobic training, despite slightly lower perfusion in DS before training; these findings were independent of interstitial NO levels. Thus, moderate aerobic training for only 10 weeks does not appear to reverse the impairment in cutaneous perfusion of the foot dorsum in response local heating in a Type 2 diabetic population.

Use of heart rate reserve and rating of perceived exertion to prescribe exercise intensity in diabetic autonomic neuropathy.

OBJECTIVE: Individuals with diabetic autonomic neuropathy (DAN) exhibit an increased resting heart rate but depressed maximal heart rate. Thus, the purpose of this study was to examine the validity of using either percent of heart rate reserve (HRR) or a rating of perceived exertion (RPE) scale to prescribe exercise intensity in diabetic individuals both with and without DAN. RESEARCH DESIGN AND METHODS: The subjects consisted of 23 individuals with type 2 diabetes, ages 45-75 years, with (DAN; n = 13) or without (No DAN; n = 10) clinical signs of DAN, as assessed by heart rate variability using the expiration-to-inspiration ratio of the R-R interval. Peak aerobic capacity was determined using a graded protocol on a cycle ergometer, with RPE, heart rate, and VO(2) values recorded at each stage. RESULTS: The subjects were similar with the exception of depressed autonomic function in DAN subjects. Peak respiratory exchange ratio values were significantly higher (P < 0.05) in the DAN group (1.08 +/- 0.02 vs. 1.02 +/- 0.01 in No DAN subjects), although DAN subjects exhibited a significantly lower (P < 0.05) peak exercise heart rate. A similarly highly linear relationship between %HRR and percent VO(2) reserve (VO(2)R) existed for both groups (r = 0.98). A similar slightly weaker relationship (r = 0.94) was found between RPE and %VO(2)R. CONCLUSIONS: In conclusion, in diabetic individuals, %HRR provides an accurate prediction of %VO(2)R and can be used to prescribe and monitor exercise intensity, regardless of the presence of DAN. The RPE scale is also a valid, albeit slightly less accurate, method to monitor exercise intensity in diabetic individuals.

Is there a threshold intensity for aerobic training in cardiac patients?

PURPOSE: Recent guidelines have recommended the use of a percentage of oxygen uptake reserve (VO2R) for prescribing aerobic exercise intensity for cardiac patients. Moreover, these guidelines suggest that a threshold intensity may exist, below which no improvement in peak oxygen uptake (VO2peak) occurs. The purpose, therefore, was to translate the intensity of aerobic exercise in previous training studies using cardiac patients into %VO2R units, and determine whether a threshold intensity exists. METHODS: Twenty-three studies, using 28 groups of aerobically trained cardiac patients, were identified in which VO2peak was measured before and after training by gas exchange. Intensity of exercise was variously described as a percentage of VO2peak, percentage of peak heart rate (HRpeak), percentage of heart rate reserve (HRR), or percentage of peak workload. These intensities were translated into equivalent units of %VO2R. RESULTS: Of the 28 groups of patients, three failed to show significant improvements in VO2peak. These groups exercised at intensities corresponding to 47-55% of VO2R. However, six other groups exercised at comparable intensities (i.e., 42% to 55% of VO2R) and experienced significant increases in VO2peak. Other confounding variables in these studies were similar, including the initial VO2peak of the subjects, suggesting that the failure of three groups to significantly improve aerobic capacity was due to their small sample size. CONCLUSION: No threshold intensity for aerobic training was identified in cardiac patients, with the lowest intensity studied being approximately 45% of VO2R. It is possible that intensities below this value may be an effective training stimulus, especially in extremely deconditioned subjects, but further research is needed to test that possibility and to determine whether a threshold exists.

VO(2) reserve and the minimal intensity for improving cardiorespiratory fitness.

PURPOSE: The American College of Sports Medicine has stated that aerobic training needs to occur at a minimum threshold intensity of 50% VO(2max) for most healthy adults and at 40% VO(2max) for those with a very low initial fitness. Recently, the concept of VO(2) reserve (%VO(2R), i.e., a percentage of the difference between maximum and resting VO(2)) has been introduced for prescribing exercise intensity. This analysis was designed to determine the threshold intensity for improving cardiorespiratory fitness expressed as %VO(2R) units. METHODS: Previous studies in healthy subjects (N = 18) that evaluated the results of training at low-to-moderate intensities (i.e., < or = 60% VO(2max)) were identified. The original studies described the intensity of exercise variously as %VO(2max), %HRR, %HR(max), or as a specific HR value. In each case, the intensity was translated into %VO(2R) units. RESULTS: Exercise training intensities below approximately 45% VO(2R) were consistently ineffective at increasing VO(2max) in studies that used subjects with mean initial VO(2max) values > 40 mL x min(-1) x kg(-1). In studies using subjects with mean initial VO(2max) values < 40 mL x min(-1) x kg(-1), no intensity was found to be ineffective. For this latter group of subjects, the lowest intensities examined were approximately 30% VO(2R). CONCLUSION: Although evidence for a threshold intensity was not strong, this analysis of training studies supports the use of 45% VO(2R) as a minimal effective training intensity for higher fit subjects and 30% VO(2R) for lower fit subjects.

Validation of a new method for estimating VO2max based on VO2 reserve.

PURPOSE: The American College of Sports Medicine's (ACSM) preferred method for estimating maximal oxygen consumption (VO2max) has been shown to overestimate VO2max, possibly due to the short length of the cycle ergometry stages. This study validates a new method that uses a final 6-min stage and that estimates VO2max from the relationship between heart rate reserve (HRR) and VO2 reserve. METHODS: A cycle ergometry protocol was designed to elicit 65-75% HRR in the fifth and sixth minutes of the final stage. Maximal workload was estimated by dividing the workload of the final stage by %HRR. VO2max was then estimated using the ACSM metabolic equation for cycling. After the 6-min stage was completed, an incremental test to maximal effort was used to measure actual VO2max. Forty-nine subjects completed a pilot study using one protocol to reach the 6-min stage, and 50 additional subjects completed a modified protocol. RESULTS: The pilot study obtained a valid estimate of VO2max (r = 0.91, SEE = 3.4 mL x min(-1) x kg-1) with no over- or underestimation (mean estimated VO2max = 35.3 mL x min(-1) x kg(-1), mean measured VO2max = 36.1 mL x min(-1) x kg(-1)), but the average %HRR achieved in the 6-min stage was 78%, with several subjects attaining heart rates considered too high for submaximal fitness testing. The second study also obtained a valid estimate of VO2max (r = 0.89, SEE = 4.0 mL x min(-1) x kg(-1)) with no over- or underestimation (mean estimated VO2max = 36.7 mL x min(-1) x kg(-1), mean measured VO2max = 36.9 mL x min(-1) x kg(-1), and the average %HRR achieved in the 6-min stage was 64%. CONCLUSIONS: A new method for estimating VO2max from submaximal cycling based on VO2 reserve has been found to be valid and more accurate than previous methods.

Childhood obesity's relationship to time spent in sedentary behavior.

OBJECTIVE: The purpose of this study was to evaluate various types of sedentary behavior children participate in and to look for an association to childhood obesity. METHODS: Questionnaires were used to gather data on physical and sedentary activity, dietary intake, demographics, and anthropometrics of 9- to 12-year-old military dependents and their parents. RESULTS: Using body mass index (BMI), 39.8% of children were obese. A significant relationship was found between childhood obesity and computer usage, television watching, total hours in sedentary behavior, and maternal BMI. An indirect significant relationship with childhood obesity was also shown if a parent was home when the child got home from school and if a father participated in exercise with their child. Caloric intake, total time in physical activity, demographic variables, and father's BMI showed no significant relationship with children's BMI. CONCLUSION: Interventions should be designed targeting total time spent on the computer, total time watching television, and maternal obesity in child obesity programs.

The effects of acute hypoxia and exercise on marksmanship.

PURPOSE: This study evaluated the effects of acute hypoxia and physical exertion on marksmanship. METHODS: At each of five simulated altitudes (162 m, SL; 1015 m, 1K; 2146 m, 2K; 3085 m, 3 K; 3962 m, 4 K), subjects performed four shooting trials: at rest, immediately after a 60-s run with load, and twice more separated by 30-s rest. Arterial oxygen saturation (SaO2), HR, and ventilation rate (VR) were recorded. RESULTS: Both increasing altitude and exercise significantly (P < 0.05) decreased marksmanship. The shooting scores at 4 K were significantly lower than those at all other altitudes. There was a likely trend for scores at 3 K to be lower than those at SL and 1K (P = 0.06 and 0.07, respectively). The shooting score at rest was significantly greater than that in all trials after exercise. Partial recovery of marksmanship after exercise occurred. Altitude and exercise both significantly reduced SaO2 and increased VR. HR did not change with altitude but increased after exercise. There was a strong positive correlation (r = 0.84) between marksmanship and SaO2. There was a strong inverse correlation (r = -0.72) between marksmanship and VR, and a modest inverse correlation (r = -0.54) between marksmanship and HR. CONCLUSIONS: Increasing altitude impaired marksmanship, with a threshold at 3000-4000 m. The decreased marksmanship was closely related to decreased arterial oxygen saturation and increased ventilation, the latter increasing movement of the chest wall.