Scott W. Arnett

Aerobic reserve and physical functional performance in older adults

BACKGROUND older adults can be limited in their performance of daily tasks due to an inadequate aerobic capacity. Aerobic capacity below minimum physiological thresholds required to maintain independence leaves older adults with little, or no, aerobic reserve. OBJECTIVE the aim of this study was to measure functional performance and aerobic reserve in older adults during the serial performance of daily tasks. SUBJECTS twenty-nine (n = 29) men and women (n = 23 females) 70-92 years of age participated in this study. METHODS performance based physical function was assessed using the Continuous-Scale Physical Functional Performance test (CS-PFP). A Cosmed K4b(2) portable metabolic system was used to measure VO(2PEAK) and oxygen uptake during the serial performance of a battery of daily tasks (VO(2PFP)). Aerobic reserve was calculated as the difference between VO(2PEAK) and VO(2PFP). RESULTS the correlation coefficient between aerobic reserve and functional performance was r = 0.50(P = 0.006). Participants utilized 32.2 +/- 8.1%, 42.7 +/- 10.8%, and 50.3 +/- 12.3% of VO(2PEAK) for the low, moderate, and high workloads of the CS-PFP, respectively. CONCLUSIONS light housework and carrying groceries require 40 to 50% of peak oxygen consumption. This information can be used by clinicians and health professionals working with older adults as a guide to how much aerobic fitness is needed to perform ADLs and maintain independence. These can then be used as guides for assessment and for setting training goals in older adults.

Exercise Intensity and Lymphocyte Subset Apoptosis

This investigation assessed the lymphocyte subset response to increasing intensity. Participants completed an exertion test (VO(2max)), and later performed a 10-min run at 76% VO(2max), 5-min at 87%, and run to exhaustion at 100% intensity. Blood was sampled at rest, following each intensity, and 1-h post. Cell concentration, apoptosis (annexin V) and migration (CX₃CR1) were evaluated in CD4+, CD8+, and CD19+ subsets. Relative data were analyzed using 1-way ANOVA with significance at P≤0.05. Absolute changes from rest (Δ baseline) were calculated for exercise conditions. CX₃CR1 displayed relative changes 1-h post, (CD8+ Pre=58%, Post=68%, 1 h-Post=37%, P=0.04) (CD19+ Pre=1.9%, Post=3.2%, 1 h-Post=5.2%, P=0.02). No relative changes were noted for subsets and annexin V. Absolute changes revealed that CD4+/annexin V+ and CD8+/annexin V+ significantly increased at 76%,(P<0.01). Significant absolute increases were observed in CD4+/CX₃CR1 at 87% VO2max, and at 87% and 100% VO2max in CD8+/CX₃CR1 (P<0.01). Subsets respond differently with intensity with respect to cell count, and markers of apoptosis and cell migration. CD4+ and CD8+ appear to be prone to apoptosis with moderate exercise, but significant increases in migration at higher intensities suggests movement of these cells from the vasculature in postexercise measurements.

Repeated high-intensity Wingate cycle bouts influence markers of lymphocyte migration but not apoptosis

Studies have shown significant changes in lymphocytes during continuous exercise, but little has been shown on the effect of repeated high intensity bouts. This study was designed to examine the effect of repeated intermittent bouts on lymphocyte subset cell count, apoptosis, and migration. A series of 6 Wingate anaerobic cycle tests were performed by participants (N = 8) with blood samples attained before, immediately following, and after a designated recovery period (excess postexercise oxygen consumption (EPOC)) to observe lymphocyte changes. Lymphocyte subsets (CD4+, CD4/CD45RA+, CD8+, CD8+/CD45RA+, CD19+) were assessed for apoptosis (annexin V+) and cellular migration (CX(3)CR1). Our results indicate that the CD8+ and CD8+/CD45RA+ subsets were significantly influenced by the repetitive Wingate cycling protocol such that cell counts increased with exercise, and then decreased at EPOC termination (p = 0.016). The observed postexercise decrease in CD8+ and CD8+/CD45RA+ cells was accompanied by a significant change in the CX(3)CR1 cell migration receptor (p = 0.019), but not apoptosis (p = 0.87). This indicates that with repetitive high-intensity cycling, the response in CD8+ cells following the bout is likely due to cell migration rather than cell death.

Finger-stick Blood Sampling Methodology for the Determination of Exercise-induced Lymphocyte Apoptosis

Exercise is a physiological stimulus capable of inducing apoptosis in immune cells. To date, various limitations have been identified with the measurement of this phenomenon, particularly relating to the amount of time required to isolate and treat a blood sample prior to the assessment of cell death. Because of this, it is difficult to determine whether reported increases in immune cell apoptosis can be contributed to the actual effect of exercise on the system, or are a reflection of the time and processing necessary to eventually obtain this measurement. In this article we demonstrate a rapid and minimally invasive procedure for the analysis of exercise-induced lymphocyte apoptosis. Unlike other techniques, whole blood is added to an antibody panel immediately upon obtaining a sample. Following the incubation period, red blood cells are lysed and samples are ready to be analyzed. The use of a finger-stick sampling procedure reduces the volume of blood required, and minimizes the discomfort to subjects.

Specificity of training modalities on upper-body one repetition maximum performance: free weights vs. hammer strength equipment.

Lyons, TS, McLester, JR, Arnett, SW, and Thoma, MJ. Specificity of training modalities on upper-body one repetition maximum performance: free weights vs. hammer strength equipment. J Strength Cond Res 24(11): 2984-2988, 2010-The purpose of this study was to determine whether a relationship exists between 1-repetition maximum (1RM) performed on hammer strength (HS) machines compared to free weights (FWs) and also to develop regression equations that can accurately predict 1RM when switching from exercise modality to another. Thirty-one trained male subjects performed 1-RM lifts (1RMs) on 3 HS externally loaded machines and 3 comparable FW exercises. Subjects performed 2 1RM tests during each laboratory session, with at least 48-72 hours of recovery between each. One repetition maximum data were used to (a) determine the relationship between 1RM performed on HS vs. FW and (b) to develop regression equations that can accurately predict 1RMs when switching from 1 exercise modality to another. Statistics revealed significant differences (p < 0.05) between 1RMs performed on the HS equipment as compared to its corresponding (FW) exercise. For all exercises, 1RMs were significantly greater on the HS equipment. Regression equations were developed for all exercises, except when predicting the HS shoulder press and the HS preacher curls from their free weight counterparts, where no variables existed that could significantly predict their respective 1RMs. As 1 RMs were significantly greater when using the HS equipment compared to when using FWs, those transitioning from HS exercise to FW exercise should exercise caution.

The effects of a lateral in-flight perturbation on lower extremity biomechanics during drop landings

One potential ACL injury situation is due to contact with another person or object during the flight phase, thereby causing the person to land improperly. Conversely, athletes often have flight-phase collisions but do land safely. Therefore, to better understand ACL injury causation and methods by which people typically land safely, the purpose of this study was to determine the effects of an in-flight perturbation on the lower extremity biomechanics displayed by females during typical drop landings. Seventeen collegiate female recreational athletes performed baseline landings, followed by either unexpected laterally-directed perturbation or sham (nonperturbation) drop landings. We compared baseline and perturbation trials using paired-samples t tests (P < .05) and 95% confidence intervals for lower-extremity joint kinematics and kinetics and GRF. The results demonstrated that perturbation landings compared with baseline landings exhibited more extended joint positions of the lower extremity at initial contact; and, during landing, greater magnitudes for knee abduction and hip adduction displacements; peak magnitudes of vertical and medial GRF; and maximum moments of ankle extensors, knee extensors, and adductor and hip adductors. We conclude that a lateral in-flight perturbation leads to abnormal GRF and angular motions and joint moments of the lower extremity.

Cognitive awareness of carbohydrate intake does not alter exercise-induced lymphocyte apoptosis

OBJECTIVE: The purpose of this investigation was to determine whether cognitive awareness of carbohydrate beverage consumption affects exercise‐induced lymphocyte apoptosis, independent of actual carbohydrate intake. INTRODUCTION: Carbohydrate supplementation during aerobic exercise generally protects against the immunosuppressive effects of exercise. It is not currently known whether carbohydrate consumption or simply the knowledge of carbohydrate consumption also has that effect. METHODS: Endurance trained male and female (N  =  10) athletes were randomly assigned to one of two groups based on either a correct or incorrect cognitive awareness of carbohydrate intake. In the incorrect group, the subjects were informed that they were receiving the carbohydrate beverage but actually received the placebo beverage. Participants completed a 60‐min ride on a cycle ergometer at 80% VO2peak under carbohydrate and placebo supplemented conditions. Venous blood samples were collected at rest and immediately after exercise and were used to determine the plasma glucose concentration, lymphocyte count, and extent of lymphocyte apoptosis. Cognitive awareness, either correct or incorrect, did not have an effect on any of the measured variables. RESULTS: Carbohydrate supplementation during exercise did not have an effect on lymphocyte count or apoptotic index. Independent of drink type, exercise resulted in significant lymphocytosis and lymphocyte apoptosis (apoptotic index at rest  =  6.3±3% and apoptotic index following exercise  =  11.6±3%, P<0.01). CONCLUSION: Neither carbohydrate nor placebo supplementation altered the typical lymphocyte apoptotic response following exercise. While carbohydrate supplementation generally has an immune‐boosting effect during exercise, it appears that this influence does not extend to the mechanisms that govern exercise‐induced lymphocyte cell death.

Effects of a Simulated Tennis Match on Lymphocyte Subset Measurements

Tennis is an activity requiring both endurance and anaerobic components, which could have immunosuppressive effects postexercise. Purpose The purpose of this investigation was to determine the effect of a simulated tennis match on apoptotic and migratory markers on lymphocyte subsets. Method Male high school (n = 5) and college (n = 3) tennis players (M age = 18.9 ± 3.3 years) completed 10 sets of a tennis protocol including serves, forehand strokes, and backhand groundstrokes with 1-min rest periods between sets. Apoptosis antigen 1 receptor (CD95) and chemokine receptor fractalkine (CX3CR1) expression was analyzed on helper T lymphocytes (CD4+), cytotoxic T lymphocytes (CD8+), and B lymphocytes (CD19+) twice, at resting baseline and immediately after all 10 sets of the tennis protocol. Results An increase was observed in each lymphocyte subtype (p < .02, effect size = .41), and comparison of absolute changes revealed increases in CD4+/CD95+, CD8+/CD95+, and CD8+/CX3CR1 lymphocytes following the tennis protocol (p < .01, effect size = .43), but not in CD19+ cells. Conclusions A simulated tennis match has adequate intensity to induce immune modulations in terms of increased cell death and cellular migration in T lymphocyte subsets. Lymphocytopenia following tennis play is influenced by both apoptotic and migratory mechanisms.

The effects of an unanticipated side-cut on lower extremity kinematics and ground reaction forces during a drop landing

Abstract Unanticipated direction to cut after landing may alter the lower extremity landing biomechanics when performing landing motions. These alterations may potentially increase the risk of ACL injury. The purpose of this study was to determine if an unanticipated side-cut affects lower extremity landing biomechanics in females. Eighteen recreational female athletes participated in two blocks of testing: the first block of testing consisted of three acceptable trials of anticipated dominant limb and non-dominant limb 45-degree diagonal cutting after landing, which were performed in a counterbalanced order. The second block of testing consisted of three acceptable trials of unanticipated dominant limb and non-dominant limb diagonal cutting after landing. Data analysis mainly focused on the dominant limb landing biomechanics. Unanticipated side-cut landing, compared (paired t-test, p < 0.05) to the anticipated landings, resulted in less hip abduction and tibial internal rotation angle at initial contact (IC) and a lower maximum ankle inversion angle and a greater maximum knee abduction angle, and knee and hip displacement. Also, greater posterior GRF and a longer time to peak medial GRF were exhibited. These outcomes indicate that athletes may adapt their landing mechanics to land unsafely when encountering an unanticipated event.

Effect of a simulated tactical occupation task on physiological strain index, stress and inflammation

Background. This study aimed to evaluate the physiological strain index (PSI) along with specific immune system markers in response to a simulated firefighting occupation workload. Methods. Ten healthy male adults completed a 6-min simulated fire stair climb (SFSC) at 60 steps/min. The protocol consisted of four conditions, some including wearing a 34.04-kg vest to simulate personal protective equipment (PPE) and/or inclusion of a color-word interference test (CWIT) as a distracting mechanism. The PSI was evaluated by continuously monitoring the heart rate and core temperature. Salivary cortisol (CORT) was measured at baseline, mid SFSC and post SFSC. C-reactive protein (CRP) was evaluated at baseline and 1 h post SFSC. Results. Repeated-measures analysis of variance showed a significantly different PSI across conditions (p = 0.001). A significantly elevated PSI was exhibited during all 6 min of SFSC for both PPE and PPE + CWIT conditions. Neither CORT (p = 0.116) nor CRP (p = 0.700) was significantly different across conditions or from baseline. Conclusion. These findings suggest that firefighters are potentially at a substantial degree of physiological stress from exercise and the weight of gear alone. Further work should be conducted to further evaluate the usefulness of the PSI as a means to monitor firefighters during fire suppression.