John G. Seifert

RESPONSES TO VARYING RATES OF CARBOHYDRATE INGESTION DURING EXERCISE

The purpose of this study was to determine how the ingestion of carbohydrate at varying rates influences physiological, sensory, and performance responses to prolonged exercise at 65-75% VO2max. Ten subjects ingested either a water placebo (WP) or carbohydrate solutions formulated to provide glucose at the rates of 26, 52, and 78 g, h-1 during 2 h of cycling exercise in a cool (10 degrees C) environment. Beverages were administered in a double-blind, counterbalanced design. A 4.8 km performance test followed each 2 h session. The average time required to complete the performance test was less with the carbohydrate feedings than with WP: mean (+/- SE) for WP = 505.0 +/- 18.7 s. 26 g.h(-1) = 476.0* +/- 8.8 s. 52 g.h(-1) = 483.8 +/- 12.7 s. 78 g.h(-1) = 474.3* +/- 19.1 s; *P less than 0.05 vs WP. Carbohydrate feeding resulted in higher plasma glucose and insulin, and lower free fatty acid concentrations than did WP. Changes in plasma osmolality, plasma volume, rectal temperature, lactate, heart rate, respiratory exchange ratio, ratings of perceived exertion, and sensory responses were similar among beverage treatments. Compared with WP, ingestion of the glucose beverages minimized changes in plasma ACTH and cortisol. In summary, carbohydrate feeding at the rates of 26 and 78 g.h(-1) was associated with improved exercise performance. The data further indicate that a dose-response relationship does not exist between the amount of carbohydrate consumed during exercise and exercise performance.

The effect of fluid and carbohydrate feedings during intermittent cycling exercise

The purpose of this study was to determine the effect of ingesting water or carbohydrates solutions on physiologic function and performance during 1.6 h of intermittent cycling exercise in the heat (dry bulb temperature = 33 degrees C). Thirteen male subjects (24 to 35 yr) completed four separate rides. Each ride consisted of intermittent steady-state cycling (at 55 and 65% VO2max) interspersed with five rest periods. A timed 480 revolution cycling task completed each experimental session. During each rest period, subjects consumed 2 ml.kg-1 body weight of water placebo or solutions of 5% glucose polymer, 6% sucrose/glucose, or 7% glucose polymer/fructose. Beverages were administered in double-blind, counter-balanced order. No differences were observed among subjects in response to beverage treatments for changes in plasma concentrations of total proteins, sodium, potassium, lactate, or in osmolality, percent change in plasma volume, heart rate, oxygen uptake, respiratory exchange ratio, rating of perceived exertion, sweat rate, rectal temperature, or mean skin temperature. Compared to water placebo, the carbohydrate treatments produced higher plasma glucose values following 1 h cycling (P less than 0.01). Mean (SD) times for the 480 revolution cycling task: water placebo = 432 (43) s; glucose polymer = 401 (52) s; *sucrose/glucose = 384 (39) s; and *glucose polymer/fructose = 375 (30) s, where = P less than 0.001 compared to water placebo. Physiologic function was similarly maintained during exercise by all beverage treatments, while ingestion of sucrose/glucose and glucose polymer/fructose resulted in improved end-exercise cycling performance.

Quadriceps Muscle Function during Recreational Alpine Skiing.

PURPOSE Since the introduction of carving skis, muscle activity has been investigated primarily on expert-level skiers with respect to EMG intensities. The three-part aim of this recreational skiing study was to analyze functional differences within the quadriceps muscle, to analyze the topographical influence, and to apply a time-frequency analysis of the EMG intensities using wavelets. METHODS Seven female subjects performed two runs through a standardized corridor on a slope with different inclinations (13 degrees , 29 degrees , and 21 degrees ). Knee angle and EMG of vastus lateralis (VL) and rectus femoris (RF) of the right leg were measured during the runs. The recorded EMG signal was resolved with a set of 10 wavelets (11-432 Hz) into a time-frequency space. Subsequently, the EMG intensity and mean frequency (MF) were calculated for different time windows (inside leg; outside leg). RESULT For RF, a significantly higher MF (+15.5%, P = 0.009) but similar EMG intensities were detected in the inside leg compared with the outside leg. For VL, the MF (-9.6%, P = 0.053) and EMG intensities (-54.3%, P = 0.010) were lower in the inside leg compared with the outside leg. Both muscles responded with higher EMG intensities on increasing slope inclination (VL = 90.8%, P = 0.022; RF = 115%, P = 0.01). MF is not directly related to inclination. CONCLUSIONS Contrary to previously suggested coloading of the inside leg while carving, our results do not support this hypothesis for VL. However, the functional demand for RF in the inside leg is very high when skiing recreationally. The ability of a situation-dependent loading (RF as knee extensor) and unloading (RF as hip flexor) of the inside leg seems to be a crucial point with respect to specific fatigue during a skiing day.

Relationships between biomechanics and physiology in older, recreational alpine skiers

The aims of this applied field study were (1) to provide descriptive data on the biomechanical variables of parallel ski steering, carving in long radii and individual technique skiing modes of older recreational skiers and (2) to determine the relationships between biomechanical and physiological variables during these skiing modes. The mean knee angle (MKA), range of knee angle (RKA), ground reaction forces (GRF), co‐loading of the inner leg, mean heart rate (HRave), blood lactate (LA) and mean arterial pressure were determined for 14 older skiers (61.1 ± 5.4 years). The mean GRF did not differ between the skiing modes. Parallel ski steering resulted in a greater MKA, lower RKA and lower peak GRF compared with carving in long radii and individual technique. LA correlated positively to RKA during carving in long radii and individual technique, while HRave correlated negatively to MKA during parallel ski steering and carving in long radii. No significant relationships were found between the physiological and kinetic variables. In conclusion, dynamic skiing styles may result in increased muscle fiber recruitments, hence greater LA levels. Along with potentially greater loading of knee extensor muscles, lower MKAs may reduce perfusion and hinder substrate metabolism, consequently making ski turning more strenuous. Skiing with less knee flexion and a reduced RKAs could be recommended for older recreational skiers.

The Relationship of Heart Rate and Lactate to Cumulative Muscle Fatigue During Recreational Alpine Skiing

Seifert, J, Kröll, J, and Müller, E. The relationship of heart rate and lactate to cumulative muscle fatigue during recreational alpine skiing. J Strength Cond Res 23(3): 698-704, 2009-Common indices of fatigue may not respond similarly between downhill skiing and other activities because of the influence of factors such as snow conditions, changing terrain, and skiing style. The purpose of this study was to investigate the relationship and predictors of common fatigue indices during downhill skiing. Ten healthy female recreational skiers skied for 3 hours under standardized conditions. Feedback on heart rate (HR) and finishing time were given to each skier at the end of each run to maintain a relatively stable load. A chronic stress score (Cstress) was calculated from creatine kinase (CK), cortisol, and isometric endurance. Finishing times and HR from runs 2, 12, and 24 were similar. Heart rate averaged 82% of HRmax. Heart rate was an insignificant predictor (p = .65) and was poorly correlated (r = 0.16) to Cstress. Blood lactate (LA) was a significant predictor of the Cstress (p = 0.05; r = 0.62). Pre- to postskiing peak forces were not different (p = 0.62), but skiers experienced a significant decrease in isometric endurance from 106.1 ± 29.6 to 93.2 ± 24.0 seconds. Endurance decreased by 13%, whereas cortisol and CK increased by 16 and 42%, respectively. Isometric contraction endurance and blood LA were significant predictors of overall stress. Individual compensation mechanisms and skiing style contributed to highly variable responses during skiing. Whereas HR may indicate stress within a given run, it is not a significant indicator of Cstress and fatigue during recreational alpine skiing. However, the cumulative stress variables and LA can be used in field testing of skiers. It is suggested that LA is a practical on-hill marker of chronic stress.

The Role of Ribose on Oxidative Stress During Hypoxic Exercise: A Pilot Study

Oxygen free radicals are produced during stress, are unstable, and potentially interact with other cellular components or molecules. This reactivity can influence cellular function, including a prolongation in tissue recovery following exercise. We tested the effect of ribose (d-ribose), a pentose carbohydrate, in a double-blinded, crossover study on markers of free radical production during hypoxic exercise. Seven healthy volunteers cycled at their lactate threshold for 25 minutes while inhaling 16% O(2) with a subsequent 60-minute resting period at room air. Subjects ingested either placebo or 7 g of ribose in 250 mL of water before and after the exercise session. Urinary malondialdehyde (MDA) and plasma reduced glutathione levels increased significantly during placebo ingestion (0.2 +/- 0.03 nM/mg and 0.26 +/- 0.29 microM, respectively) but were lower with ribose supplementation (0.04 +/- 0.03 nM/mg and 0.38 +/- 0.29 microM, respectively; P < .05). Uric acid levels were similar between groups (ribose vs. placebo, 4.55 +/- 0.06 mg/dL vs. 4.67 +/- 0.06 mg/dL). Ribose demonstrated a beneficial trend in lower MDA and reduced glutathione levels during hypoxic stress.

A heat and moisture mask attenuates cardiovascular stress during cold air exposure.

Background: Exposure to cold has been shown to cause cardiovascular stress and increased morbidity and mortality. Inhalation of cold, dry air can increase blood pressure and induce myocardial ischemia, particularly in people with preexisting hypertensive cardiovascular disease. Face masks that can warm and humidify inhaled cold air may reduce these cold air pressor effects. Method: We compared blood pressure measurements using a heat and moisture exchange mask (HME), a placebo mask (PL), and no mask (NM) in 53 patients with hypertension exposed to a cold chamber environment at −5°C for 1 h. Blood pressure and heart rate were recorded at baseline, and at 15 min intervals from 0 to 60 min of chamber exposure. All patients were taking antihypertensive medications with drug and dosage determined by their own physicians. Data were analyzed by a one-way analysis of variance test with repeated measures, and significant interactions were analyzed by Fisher’s least significant differences tests. A post hoc subgroup analysis for the effect of age was performed using Wilcoxon matched-pair rank tests. Results: Wearing the HME resulted in significantly lower systolic and mean arterial blood pressures than the PL and NM conditions. Diastolic blood pressures were significantly lower for the HME than the NM, but not the PL condition. Conclusion: Subgroup analyses suggested that the effect of the HME in mitigating systolic blood pressure increase from inhalation of cold air was significantly greater for patients aged 60 years or over than for those under 60 years.

Instructor-Paced vs. Self-Paced Skiing Modes in Older Recreational Alpine Skiers

Scheiber, P, Seifert, JG, and Müller, E. Instructor-paced vs. self-paced skiing modes in older recreational alpine skiers. J Strength Cond Res 25(4): 988-996, 2011-Parallel ski steering (PSS), carving in long radii (CLR), and individual technique (IT) skiing modes are mainly used throughout instructor-guided skiing of older recreational skiers. The aims of this study were (a) to determine differences in the physiologic response of older skiers to PSS, CLR, and IT skiing modes, (b) to quantify correlations between rate of perceived exertion (RPE) and the physiologic response, and (c) to analyze the relationship between aerobic capacity, skiing skills, and the blood lactate (LA) response during instructor-guided skiing. Twenty recreational skiers (61.1 ± 5.6 years) performed instructor-paced (PSS and CLR) and self-paced (IT) skiing modes. Heart rate (HR), LA, mean arterial blood pressure (MAP), and RPE were determined during skiing. Skiers skiing skills were judged by expert ski instructors. The aerobic capacity was tested by a physical work capacity test (PWC130) test. Heart rate was lower for PSS (106 ± 15 b·min−1), compared to CLR (118 ± 16 b·min−1) and IT (120 ± 15 b·min−1) skiing modes, both p < 0.001. Lactate levels were 1.45 ± 0.50 mmol·L−1 for PSS, 1.67 ± 0.61 mmol·L−1 for CLR, and 2.00 ± 0.74 mmol·L−1 for IT skiing modes, all p < 0.004. Individual reductions in LA concentrations from 3.9 to 2.6 mmol·L−1 were found, for IT and PSS skiing modes, respectively. No significant correlations were determined between any physiologic variable and RPE. Weak correlations were found between LA and PWC130 results (R2 < 0.114) and between LA and skiing skills (R2 < 0.132). In conclusion, significant reductions in the physiologic response were determined for PSS and CLR, compared with IT skiing modes. Instructor-paced skiing modes may minimize the risk of premature fatigue of skiers with high physiological responses. Those skiers may not perceive their disproportionate higher stress compared with skiers on the low end.

Alpine Skiing With total knee ArthroPlasty (ASWAP) : symmetric loading during skiing

The aim of this pilot study was to determine the pressure distribution, symmetry of load between operated (OP) and non‐operated (NOP) leg, and pain level during alpine skiing in participants with unilateral total knee arthroplasty (TKA). The responses of the dependent variables were analyzed following a 10‐week guided skiing intervention of 2–3 days of skiing per week. Ground reaction force (GRF) was recorded bilaterally and was determined for 13 participants with TKA (65 ± 4 years) at pre‐ and post‐test. Additionally, pain perception was determined using a numeric rating scale in the OP leg at both test sessions and after each skiing day. No statistical differences were observed between OP and NOP legs for peak and average GRF as well as the asymmetry indices at pre‐test. Pain perception was low and was not increased as a consequence of the skiing intervention. In conclusion, alpine skiing did not lead to increased or decreased loading of the OP leg compared with the NOP leg. Therefore, alpine skiing may be allowed for patients with skiing experience and a good clinical outcome.

Supplements for exercise.

Athletes, and to a lesser degree “weekend warriors,” are always looking for an edge to physically maintain or excel in their exercise performance, lessen muscular soreness, minimize fatigue, and speed recovery. To try to achieve this state, many have turned to nutritional supplements. However, in order to effectively promote and maintain acceptance by the public, well-structured studies with finite endpoints must be performed with high standards and accurately reported in reputable journals to satisfy interested parties. Researchers have addressed a more effective means in replenishing muscular energy levels postexercise, as well as reducing soreness and fatigue, resulting in a more rigorous training schedule. Furthermore, the production of oxygen-free radicals during and following exercise has attracted attention over the past decade. These free radical compounds have the potential to harm the cell’s wall and hinder intracellular processes. Therefore, today’s sports medicine market has entertained products that have the potential to lessen this cellular energy drain, minimize the damaging effects from formed oxygen-free radicals during and following exercise, and offer the means to maintain or potentially exceed performance goals. However, finding effective supplements in meeting these goals is often more difficult than not. Many individuals find that the advertised benefits of a supplement from information found in the media, including the Internet, do not always live up to their claims, which casts not only doubt about the product but also questions credibility in the nutraceutical industry. The goal of an energy supplement should center on replenishing energy most effectively and quickly following a workout session.