Recovery of hormonal, blood lipid, and hematological profiles from a North Pole expedition.

INTRODUCTION: This study examined the recovery patterns of hormonal, blood lipid, and hematological profiles following strenuous physical loading, continuous extreme cold exposure and energy deficit induced by a North Pole expedition. METHODS: Seven men completed an 850-km North Pole expedition in temperatures varying from -3 degrees C to -47 degrees C. Daily energy intake was approximately 23 MJ x d(-1) and was composed of approximately 60% fat. Blood samples were collected 2 wk before (Pre) the expedition and after 2 wk (Post 1), and 2 mo (Post 2). Additional samples were collected on the first (R1), third (R3), and fifth (R5) return days. RESULTS: Mean weight loss upon return was 10 kg. Energy expenditure was estimated to be 29.6 MJ x d(-1). Declines in cortisol (-237.29 nmol x L(-1)), total testosterone (-5.08 nmol x L(-1)), bioavailable testosterone (-0.37 nmol x L(-1)) and free thyroxin (-5.82 pmol x L(-1)) returned to normal values at R5 or Post 1 (P < 0.05). The increase in sex hormone-binding globulin (+17.5 nmol x L(-1)) rapidly returned to the pre-expedition concentration at R3 (P < 0.05). Significantly greater values were observed at Post 1 in the lipid (high-density lipoprotein +1.86 mmol x L(-1); low-density lipoprotein +4.23 mmol x L(-1)) and hematological (WBC +1.28 x 10(3)/L; platelets +51.86 x 10(3)/L) profiles (P < 0.05). RBC, hemoglobin, and hematocrit were all lower at Post 1 (P < 0.05). CONCLUSION: Although the expedition generated extreme physical stress, this was not directly reflected on hormonal recovery times as it was similar to other much less strenuous events. Despite important variations, all hormones returned to baseline values within 2 wk. Nonetheless, physical stress would appear to have more long-term effects on blood lipid and hematological profiles.

Effects of aerobic and strength training on aerobic capacity, muscle strength, and gene expression of lymphomonocytes in patients with stable CAD.

This study examined the effectiveness, suitability, and safety of a mixed interval-type aerobic and strength training program (MIAST) on physical fitness in patients with stable coronary artery disease (CAD) without history of myocardial infarction (MI). Twenty-three patients with stable CAD were randomly assigned to a MIAST (n = 12; mean age 58.6 years) or control (n = 11; 63.3 years) group. The MIAST group participated in the progressive training program twice a week for 21 weeks. Peak oxygen uptake (VO2peak), workload, and exercise time were measured as were maximal muscle strength, serum lipids, glucose concentration, and the cross-sectional area (CSA) of knee extensors. The safety and suitability of the program were assessed by wireless electrocardiogram (ECG) monitoring and exercise diaries. VO2peak (6.9%; P < 0.05) and exercise time (11.2%; P < 0.05) improved significantly after 12 weeks of training in the MIAST group compared to the control group. Muscle strength (19.9%; P < 0.05) and CSA (2.2%; P < 0.05) increased, and serum lipids and blood glucose tended to decrease after the training. The successful training program (increase in maximal oxygen uptake) increased the gene expression of oxygen metabolism and decreased the gene expression of inflammation pathways in lymphomonocytes. The MIAST program, including interval-type aerobic and strength training, was safe, did not cause any adverse effects, and led to significant improvements in physical fitness in patients with stable CAD.

Resistance exercise-induced hormonal responses in men, women, and pubescent boys.

PURPOSE: This study was designed to investigate the acute plasma catecholamine (CA) response to resistance exercise and its association with serum testosterone (TES), cortisol (COR), and growth hormone (GH) concentration changes. METHODS: Six men, six women, and six adolescent boys (14 +/- 0 yr) performed five sets of 10 knee extensions with 40% of one-repetition maximum followed by two sets performed to exhaustion. Arterialized venous blood was sampled before, during, and after the exercise for the hormone analysis. External work performed (Wext), average EMG normalized for maximal EMG, exercise-induced maximal voluntary contraction decline, and plasma volume change (deltaPV) were also determined. RESULTS: No differences between groups were observed in Wext relative to lean body mass, average EMG, or in exercise-induced fatigue. Plasma norepinephrine (NE) concentrations were similar in the three groups. However, peak plasma epinephrine (E) increase from preexercise was about twice as high in boys (5.0 +/- 2.6 nmol.L-1 as in men (2.5 +/- 0.8 nmol.L-1] and in women (2.1 +/- 0.6 nmol.L-1) (P < 0.05). The deltaPV could explain a significant increase in serum TES concentration in men, and increases in GH concentrations in every group, but not that of COR observed only in boys. No correlation between the CA concentration changes and those of the other hormones were observed even if the groups were combined. CONCLUSION: No associations between the CA and the other hormone responses were observed. However, the results may suggest a trend for higher stress response to this particular exercise in the boys than in adults.

EMG, heart rate, and accelerometer as estimators of energy expenditure in locomotion.

PURPOSE: Precise measures of energy expenditure (EE) during everyday activities are needed. This study assessed the validity of novel shorts measuring EMG and compared this method with HR and accelerometry (ACC) when estimating EE. METHODS: Fifty-four volunteers (39.4 ± 13.9 yr) performed a maximal treadmill test (3-min loads) including walking with different speeds uphill, downhill, and on level ground and one running load. The data were categorized into all, low, and level loads. EE was measured by indirect calorimetry, whereas HR, ACC, and EMG were measured continuously. EMG from quadriceps (Q) and hamstrings (H) was measured using shorts with textile electrodes. Validity of the methods used to estimate EE was compared using Pearson correlations, regression coefficients, linear mixed models providing Akaike information criteria, and root mean squared error (RMSE) from cross-validation at the individual and population levels. RESULTS: At all loads, correlations with EE were as follows: EMG(QH), 0.94 ± 0.03; EMG(Q), 0.91 ± 0.03; EMG(H), 0.94 ± 0.03; HR, 0.96 ± 0.04; and ACC, 0.77 ± 0.10. The corresponding correlations at low loads were 0.89 ± 0.08, 0.79 ± 0.10, 0.93 ± 0.07, 0.89 ± 0.23, and 0.80 ± 0.07, and at level loads, they were 0.97 ± 0.03, 0.97 ± 0.05, 0.96 ± 0.04, 0.95 ± 0.08, and 0.99 ± 0.02, respectively. Akaike information criteria ranked the methods in accordance with the individual correlations. CONCLUSIONS: It is shown for the first time that EMG shorts can be used for EE estimations across a wide range of physical activity intensities in a heterogeneous group. Across all loads, HR is a superior method of predicting EE, whereas ACC is most accurate for level loads at the population level. At low levels of physical activity in changing terrains, thigh muscle EMG provides more accurate EE estimations than those in ACC and HR if individual calibrations are performed.

Muscle activity and inactivity periods during normal daily life.

Recent findings suggest that not only the lack of physical activity, but also prolonged times of sedentary behaviour where major locomotor muscles are inactive, significantly increase the risk of chronic diseases. The purpose of this study was to provide details of quadriceps and hamstring muscle inactivity and activity during normal daily life of ordinary people. Eighty-four volunteers (44 females, 40 males, 44.1±17.3 years, 172.3±6.1 cm, 70.1±10.2 kg) were measured during normal daily life using shorts measuring muscle electromyographic (EMG) activity (recording time 11.3±2.0 hours). EMG was normalized to isometric MVC (EMG(MVC)) during knee flexion and extension, and inactivity threshold of each muscle group was defined as 90% of EMG activity during standing (2.5±1.7% of EMG(MVC)). During normal daily life the average EMG amplitude was 4.0±2.6% and average activity burst amplitude was 5.8±3.4% of EMG(MVC) (mean duration of 1.4±1.4 s) which is below the EMG level required for walking (5 km/h corresponding to EMG level of about 10% of EMG(MVC)). Using the proposed individual inactivity threshold, thigh muscles were inactive 67.5±11.9% of the total recording time and the longest inactivity periods lasted for 13.9±7.3 min (2.5-38.3 min). Women had more activity bursts and spent more time at intensities above 40% EMG(MVC) than men (p<0.05). In conclusion, during normal daily life the locomotor muscles are inactive about 7.5 hours, and only a small fraction of muscle's maximal voluntary activation capacity is used averaging only 4% of the maximal recruitment of the thigh muscles. Some daily non-exercise activities such as stair climbing produce much higher muscle activity levels than brisk walking, and replacing sitting by standing can considerably increase cumulative daily muscle activity.

Muscle loading and activation of the shoulder joint during humeral external rotation by pulley and variable resistance.

BACKGROUND: The aim of the study was to evaluate differences in the loading of glenohumeral joint muscles between a cable pulley machine (CP) and variable resistance machine (VR) during axial humeral external rotation. METHODS: Eleven healthy male subjects took part in the study. Intramuscular electromyography from five muscles of the shoulder (medial deltoid, supraspinatus, infraspinatus and upper part of the trapezius), torque and power output was measured at different rotation angles and with different loads (10%, 50% and 100% of 1RM). Also the compressive and shear force in the glenohumeral joint was analyzed at the horizontal level at angles of rotation. External rotation was performed with a self-selected velocity on the scapular plane. FINDINGS: In the CP the range of movement became narrower than in the VR with increasing workload (P<0.05). The activity of the infraspinatus did not grow in the CP after 50% load, while it did in the VR (P<0.01). The upper part of the trapezius was activated less in the CP than in the VR (P<0.01) machine when using 50% and 100% loads. In comparison with the CP, the shear forces that pull the head of the humerus in a posterior direction were more evenly distributed in the VR than in the CP at different angles of rotation (P<0.001). INTERPRETATION: The VR seems to make a broader range of motion possible, lager activation the primary external rotators and evenly distributed shear forces than the CP. However, performing the exercise with VR and high load also activates the upper part of the trapezius. RELEVANCE: These findings can be used in the development of exercise designs, methods and equipment for shoulder injury rehabilitation.

Hormonal responses during a prolonged military field exercise with variable exercise intensity.

The purpose of the present study was to test the hypothesis that the magnitude of hormonal concentration alterations during a prolonged military field exercise with constant energy intake (EI) is influenced by changes in energy deficit (ED) induced by varying the exercise intensity. Basal serum hormone concentrations were measured in a group of healthy young male volunteers (n = 7) during a 20-day field exercise. During the first week of the exercise, the average ED was 4,000 kcal/day (P-I), in the second week only 450 kcal/day (P-II), and in the last week 1,000 kcal/day (P-III). During the first 5 days of the field exercise, significant increases in cortisol (COR, +32%) and growth hormone (GH, +616%) concentrations were observed, while insulin (INS, -70%), total testosterone (TES, -27%), free testosterone (TES(free), -26%) decreased. However, after these initial responses, COR and GH returned to the pre-exercise level by the beginning of P-II. Also TES and TES(free) recovered to the pre-exercise level by the beginning of P-III, and INS by the end of P-III. The concentration of TES (+29%) increased above the pre-exercise level by the beginning of P-III. Serum thyroxin (T(4)) concentration was significantly lesser (-12%) and urine urea concentration significantly higher (+78%) after the field exercise than before it. Therefore, it can be concluded that the lower levels of ED in the second and third phase (ED <1,000 kcal/day) allowed recovery of hormonal changes observed in the first phase with ED much greater than 1,000 kcal/day.

Estimation of maximal heart rate using the relationship between heart rate variability and exercise intensity in 40-67 years old men.

Large interindividual variation in maximal heart rate (HRmax) may not be accounted for by age alone. In order to evaluate a novel method in the prediction of HRmax, this study examined the profile of HR variability (HRV) during exercise in 40-67 years old men (n = 74). R-R intervals were recorded during supine rest and during a graded exercise test by cycle ergometry until exhaustion. A third-degree polynomial function was fitted to the HRV data recorded during exercise to represent the HRV profile of each subject. The instantaneous beat-to-beat R-R interval variability (SD1), high (HF) and low frequency power decreased between all consecutive exercise intensities (P < 0.033). The relationship between HRmax and a variable illustrating the declining rate of HF (HRHF50%) was stronger (r = 0.50, P < 0.001) than between HRmax and age (r = -0.36, P < 0.01). The regression analysis showed that a more accurate estimation of HR(max) was attained when HRV was used in the equation in addition to age: HRmax = 160.633-0.603(age) + 0.441(HRHF50%) (SEE = 9.8 bpm vs. 11.6 bpm in the equation based on age alone). The decline of HRV during incremental exercise seems to be useful for accurate estimation of maximal heart rate.

Hormonal responses to a resistance exercise performed under the influence of delayed onset muscle soreness.

Hormonal responses to an unaccustomed knee-extension exercise (E1; 5 times 10 repetitions with 40% load of 1RM [1 repetition maximum] followed by 2 sets until exhaustion) were compared in 6 men with the corresponding responses to an identical exercise performed 2 days later under the influence of delayed onset muscle soreness (DOMS) (E2). Both exercises were performed with a variable-resistance machine causing exhaustion with significantly fewer repetitions than a normal constant-resistance knee-extension device does. The E1 induced DOMS as expected, but the 1RM, the total work done, and the repetition number and frequency were not different in the 2 exercises. In the 2 sets to failure, the mean repetition number varied between 17 and 25. The exercise-induced norepinephrine, epinephrine, testosterone, cortisol (COR), and growth hormone (GH) increases were similar in the 2 exercises, although the overall level of COR and GH, including the preexercise concentrations, tended to decline in the second exercise. The results may thus suggest that the hormonal response to resistance exercise is not significantly altered when performed soon after an unaccustomed exercise bout leading to DOMS.