Julia Franke

Optimal Jamar dynamometer handle position to assess maximal isometric hand grip strength in epidemiological studies.

PURPOSE Hand grip strength is an indicator of general muscle strength that is measured using a hand dynamometer. In some studies, a subjects grip strength is taken to be the maximal grip strength achieved from measurements taken at several different dynamometer handle positions. However, little is known about the influence of these different positions on the measured grip strength. The aim of the study was to identify one standard handle position that could be used to assess the grip strength of all subjects. METHODS Grip strength was assessed with a hand dynamometer (Jamar Plus+; Sammons Preston, Rolyon, Bolingbrook, IL). Each participants grip strength was measured 3 times in each of 5 different handle positions with each hand. The best position for each participant was defined as the position at which they achieved maximal grip strength. RESULTS The mean (± standard deviation) age of the 50 participants was 41 (± 13) years. Maximal grip strength was 43.7 (± 12.4) kg for all participants; 55.0 (± 10.2) kg for men and 35.4 (± 5.2) kg for women. Handle position 2 was the best position for 70% of participants. The mean difference between the grip strength achieved by each participant at handle position 2 and that achieved at each participants best position was 0.8 (± 1.78) kg. CONCLUSIONS Our results show that measurements taken at a single standard handle position are sufficiently accurate to assess grip strengths for all subjects. We therefore recommend handle position 2 as the standard position for measuring grip strength with the Jamar Plus+ hand dynamometer. CLINICAL RELEVANCE The assessment of grip strength with the Jamar Plus+ dynamometer is easier and faster if a single, standard handle position is used rather than multiple different positions. As well as providing accurate results, a single, standard handle position also reduces fatigue and increases the comparability of results between subjects.

Total hemoglobin mass, iron status, and endurance capacity in elite field hockey players.

Hinrichs, T, Franke, J, Voss, S, Bloch, W, Schänzer, W, and Platen, P. Total hemoglobin mass, iron status, and endurance capacity in elite field hockey players. J Strength Cond Res 24(3): 629-638, 2010-The aims of this study were as follows: To evaluate total hemoglobin mass (tHbmass) in international field hockey players; to examine the correlation between tHbmass and maximum oxygen uptake (&OV0312;O2max); and to assess influences of iron status on tHbmass and on &OV0312;O2max. The players of the German womens (N = 17, aged 24.8 ± 3.0 [21-31] years) and mens (N = 17, aged 24.2 ± 2.9 [19-32] years) national field hockey team were investigated. tHbmass was measured by an optimized carbon monoxide rebreathing method. The following parameters were measured in venous blood: Hemoglobin concentration (Hbconc), hematocrit (Hct), number and percentage of reticulocytes, reticulocyte hemoglobin content, serum iron, serum ferritin, serum transferrin, unsaturated iron-binding capacity, and serum soluble transferrin receptor concentration. &OV0312;O2max was determined in a treadmill test. tHbmass (women: 10.6 ± 1.1 g/kg; men: 12.5 ± 0.9 g/kg) correlated to &OV0312;O2max (women: 46.6 ± 2.9 mL/min/kg; men: 55.8 ± 4.0 mL/min/kg) in women (r = 0.56, p < 0.05) and in men (r = 0.57, p < 0.05), whereas Hbconc and Hct did not. The investigated parameters of iron status showed no association to tHbmass or to &OV0312;O2max. In conclusion, tHbmass can be used as an indicator for endurance capacity in elite field hockey players, whereas Hbconc may not. tHbmass or &OV0312;O2max were not influenced by the actual iron status of the investigated athletes.

Muscle oxygenation during exercise under hypoxic conditions assessed by spatially resolved broadband NIR spectroscopy

Near-infrared spectroscopy (NIRS) is used for the non-invasive measurement of muscle oxygenation during an incremental cycle test in healthy volunteers. A broad band spatially resolved system is used that allows the reliability of current algorithms to be inspected with the main emphasis on tissue oxygen saturation (SO2) and oxygenated and deoxygenated haemoglobin concentrations. Physiological conditions were modulated by changing oxygen supply from normal (21 % O2 in inspired air) to conditions corresponding to 2000 and 4000 m altitude above sea level (15.4 and 11.9 % O2). Under these hypoxic conditions the decrease in SO2 with increased exercise power is highly correlated with the oxygen content of the inspired air. There is a clear correlation with physiological parameters (heart rate, pulse oxymetry, blood gas, lactate, spirometric data). Skin oxygenation parameters are compared to those of muscle.

Tissue oxygenation during exercise measured with NIRS: a quality control study

We assess the data quality of calculated tissue oxygen saturation (SO2) and haemoglobin concentrations recorded on muscle during an incremental cycling protocol in healthy volunteers. The protocol was repeated three times at the same day and a fourth time at a different day to estimate the reproducibility of the method. A novel broad-band, spatially resolved spectrometer (SRS) system was employed which allowed us to compare SRS-based oxygenation parameters with modified Lambert-Beer (MLB) data. We found that the inter-subject variation in SO2 (standard deviation about 6 %) is considerably larger than the reproducibility (about 1.5 %) both for same day and different day tests. When changes in SO2 during the cycling test were considered the reproducibility is better than 1 %. Time courses of SRS-based haemoglobin parameters are different from MLB-data with higher reproducibility for SRS. The magnitudes of the haemoglobin changes were found to be considerably larger for the SRS method. Furthermore, the broad band approach was tested against a four-wavelength analysis with the differences found to be negligible.

Tissue Oxygenation During Exercise Measured with NIRS: Reproducibility and Influence of Wavelengths

Near-infrared spectroscopy (NIRS) is widely used for the measurement of skeletal muscle oxygenation during exercise as it reflects muscle metabolism, and most studies report a large variability between subjects. Here we assess the data quality of tissue oxygen saturation (SO2) and oxygenated (oxyHb) and deoxygenated (deoxyHb) haemoglobin concentrations recorded during an incremental cycling protocol in nine healthy volunteers. The protocol was repeated three times on the same day and a fourth session on a different day to estimate the reproducibility of the method with a broadband, spatially resolved spectroscopy (SRS) system. We found that the inter-subject variation in SO2 (standard deviation ≈ 6 %) was considerably larger than the reproducibility (≈ 1.5 %) both for the same-day and different-day tests. The reproducibility of changes in SO2 was better than 1 %.