Metabolic responses associated with deer hunting

History and perspectives on interval training in sport, health, and disease

Exercise can be conducted as low-intensity continuous training (LICT) or a variety of higher intensity work/rest formats, collectively called interval training. Interval training was developed for athletes in the early 20th century. It was systemized in Sweden as Fartlek, and in Germany as die interval Method, in the 1930s. Most contemporary forms of interval training evolved from these progenitors. In essence, interval training allows a large volume of high-intensity or race specific training to be performed while controlling the development of fatigue. Adding interval training to LICT done by athletes adds about 2%-4% to performance achievable with LICT, which represents a competitively meaningful difference in performance (e.g., 4:25 vs. 4:00 over 1 mile). More recently, interval training has been applied to health- fitness participants and even to patients with health conditions. Studies indicate that a comparatively low volume of interval training can produce substantial improvement in physiologic capacity, in as little as 20% of training time versus LICT. There are data indicating that interval training can be reasonably pleasant, have good adherence, and is safe, even in patients. Although interval training was originally designed for athletics, the fundamental patterns of work versus recovery are remarkably similar in healthy adults and patients. Although the total volume of training and both absolute and relative intensity and magnitude of homeostatic disturbance are larger in athletes, the overall pattern of effort is the same in fitness participants and patients. Interval training can thus be characterized as an important step in the evolution of exercise training.

Electrocardiographic Responses to Deer Hunting in Men and Women

OBJECTIVE

Deer hunting includes various stimuli resulting in augmented sympathetic activity, increased heart rate (HR) response, and rhythm changes. Collectively, these superimposed stresses may increase an individual's risk for cardiovascular events. We undertook this study to evaluate HR and rhythm responses in multiple phases of deer hunting in men and women with and without cardiovascular disease (CVD).

METHODS

Nineteen participants age 38.3 ± 13.8 years (mean ± SD) with body mass index 29.2 ± 6.9 kg/m(2) followed their normal hunting routine. HR and rhythm were recorded continuously during the hunt using a small leadless electrocardiogram (ECG) patch monitor.

RESULTS

Data were collected on 13 of 19 hunters while hiking. Three hunters recorded HR ≥85% of their age-predicted heart rate maximum (HRmax) for 1 to 2 minutes. Arrhythmias were detected in both participants with CVD and in 8 without CVD. Recorded rhythms included premature atrial, junctional, and ventricular complexes. Six hunters climbed a tree stand; 3 of them recorded HR ≥85% HRmax with sustained elevated HR response for 2 to 3 minutes with premature junctional contractions. Four of 19 participants dragged deer carcasses. During the drag, 1 male hunter recorded an HR of 91% HRmax, and another male hunter without CVD recorded an exercise-induced ischemic ECG. Fifteen of 19 hunters experienced "buck fever" (acute extreme excitation), with 7 reaching ≥85% HRmax for up to 1 minute. Ventricular bigeminy and trigeminy and ventricular couplets were observed in 1 subject during buck fever.

CONCLUSIONS

Men and women with and without CVD recorded substantial increases in HR and clinically relevant arrhythmias while deer hunting.

Cardiovascular demands of deer retrieval methods

OBJECTIVE

The purpose of this study was to compare the cardiovascular (CV) demands of 2 deer retrieval methods.

METHODS

Twelve male participants (weight 86±24 kg, age 21±1 years) performed a maximum treadmill test on day 1 to determine baseline fitness levels. On day 2, all participants first towed, then dragged a 45-kg simulated deer carcass for 457 m at a self-selected pace. The tow condition utilized a shoulder harness system with a 2-m strap connecting the harness to the carcass, allowing the participant to walk upright as he towed the load. The dragging condition required the participants to flex their trunk, grasp the legs of the deer with both hands, and drag the carcass the length of the course. Heart rate and oxygen consumption (VO2) from each trial were measured by indirect calorimetry.

RESULTS

The CV responses of towing were significantly less compared with those of dragging for VO2 peak (P=.001), peak heart rate (P=.003), average heart rate (P=.028), and rating of perceived exertion (P<.001). No significant differences were observed for average VO2 (P=.91) or time to completion (P=.27).

CONCLUSIONS

The results of this study suggest towing a deer with a shoulder harness results in significant reductions in CV demand and lower perceived exertion compared with traditional deer dragging techniques. Deer hunters who are deconditioned or have CV risk factors are strongly encouraged to consider deer retrieval methods utilizing a shoulder harness and tow rope to mitigate the increased demands commonly found with traditional retrieval methods.

Dynamic heart rate response to deer hunting in men and women

The purpose of the present study was to examine the heart rate response and force tension associated with deer hunting activities in men and women. Fifteen men and women (body mass index: 25.6±5.2 kg/m2; age: 27±9 years) participated in this study. Subjects performed a maximal graded exercise test (GXT) to determine maximal heart rate (HRmax). Subjects completed a 0.8 km hike over typical hunting terrain. Following a short rest, subjects completed a 0.4 km drag using a fake deer weighing 56 kg (123 pounds, the weight of the average field dressed deer in Pennsylvania, USA) over similar terrain. HR was measured during the activities using a Polar Heart Rate Monitor. Force tension (TNmean) while dragging the deer was measured using a cable tensiometer. Women on average completed the 0.4 km drag course in 13±3 min, where men on average only needed 6±2 min to complete the drag. Women spent significantly more time ≥85% HRmax (9±4 min), than men (2±3 min) during the drag (P<0.05). Women, on average, completed 71±22% of their drag ≥85% HRmax which was significantly greater than men (37±36%; P<0.05). Throughout the drag, men and women HRpeak corresponded to 90±6% and 99±7%, respectively, of their measured HRmax via GXT (P<0.05). No significant difference was observed in TNmean between men and women during the drag tests. The results from this study indicate that hunting includes high-intensity exercise, with a greater relative stress placed on women. Deer hunters should exercise caution and adequately prepare for the potential demands of this activity.

Consumo de oxigênio de pico em idosas: comparação entre valores medidos e previstos

O objetivo deste estudo foi comparar o consumo de oxigênio de pico (VO2pico) mensurado por meio de teste de esforço e os obtidos por equações preditivas. Participaram deste estudo 116 idosas (66,7 ± 5,8 anos), que realizaram teste ergoespirométrico em esteira. Os valores de VO2pico também foram estimados pela equação do Colégio Americano de Medicina do Esporte (ACSM) e equação de Foster. As comparações foram realizadas por meio da ANOVA para medidas repetidas. A relação entre valores da esteira e equações foi examinada pelo coeficiente de Pearson e método de Bland e Altman. As equações do ACSM e Foster superestimaram significantemente o VO2pico medido (p<0,001; diferença média de 6,9 e 2,7 ml.kg-1.min-1, respectivamente), sendo que a equação ACSM gerou valores superiores aos de Foster (p<0,05). Houve correlação positiva entre o valor do teste e o das equações (r=0,70; p<0,01), mas uma correlação negativa entre idade e VO2pico (r=-0,31; p=0,001). Os achados demonstram que para idosas, equações ergométricas comumente usadas superestimam o VO2pico em relação aos mensurados pela ergoespirometria, apontando para cautela quando da classificação da aptidão cardiorrespiratória por testes ergométricos.

Electrocardiographic responses to deer hunting activities in men with and without coronary artery disease

To evaluate the cardiac demands of hunting deer, continuous ambulatory electrocardiograms were obtained in men with and without coronary artery disease (CAD) and compared with their responses to maximal treadmill testing. A volunteer sample of 25 middle-aged men (mean +/- SD 55 +/- 7 years of age), 17 of whom had known CAD, completed the study. Peak heart rate (HR) during 7 different deer hunting activities was expressed as the mean percentage of the maximal HR (HRmax) attained during treadmill testing. Periods of sustained sinus tachycardia were identified. Arrhythmias and ST-segment depression during deer hunting that were not apparent during treadmill testing were documented. Overall, 22 of 25 subjects demonstrated HR responses >85% HRmax for 1 to 65 minutes. Ten subjects exceeded the HRmax achieved during treadmill testing for 1 to 5 minutes. The relative HR response during ambulatory activity in the field was inversely related to cardiorespiratory fitness, expressed as METs (r = -0.59; p = 0.0020). Three subjects had ischemic electrocardiograms during deer hunting, but not during treadmill testing. Complex arrhythmias in the field not detected by treadmill testing included ventricular bi-trigeminy, ventricular couplets, and 8 runs of ventricular tachycardia (3 to 28 beats) in 3 subjects with documented CAD. In conclusion, deer hunting can evoke sustained HRs, ischemic ST-segment depression, and threatening ventricular arrhythmias in excess of those documented during maximal treadmill testing. The strenuous nature of deer hunting coupled with presumed hyperadrenergia and superimposed environmental stresses may contribute to the excessive cardiac demands associated with this activity.