Marko Laaksonen

Squeezing the Muscle: Compression Clothing and Muscle Metabolism during Recovery from High Intensity Exercise

The purpose of this experiment was to investigate skeletal muscle blood flow and glucose uptake in m. biceps (BF) and m. quadriceps femoris (QF) 1) during recovery from high intensity cycle exercise, and 2) while wearing a compression short applying ∼37 mmHg to the thigh muscles. Blood flow and glucose uptake were measured in the compressed and non-compressed leg of 6 healthy men by using positron emission tomography. At baseline blood flow in QF (P = 0.79) and BF (P = 0.90) did not differ between the compressed and the non-compressed leg. During recovery muscle blood flow was higher compared to baseline in both compressed (P<0.01) and non-compressed QF (P<0.001) but not in compressed (P = 0.41) and non-compressed BF (P = 0.05; effect size = 2.74). During recovery blood flow was lower in compressed QF (P<0.01) but not in BF (P = 0.26) compared to the non-compressed muscles. During baseline and recovery no differences in blood flow were detected between the superficial and deep parts of QF in both, compressed (baseline P = 0.79; recovery P = 0.68) and non-compressed leg (baseline P = 0.64; recovery P = 0.06). During recovery glucose uptake was higher in QF compared to BF in both conditions (P<0.01) with no difference between the compressed and non-compressed thigh. Glucose uptake was higher in the deep compared to the superficial parts of QF (compression leg P = 0.02). These results demonstrate that wearing compression shorts with ∼37 mmHg of external pressure reduces blood flow both in the deep and superficial regions of muscle tissue during recovery from high intensity exercise but does not affect glucose uptake in BF and QF.

Effects of exhaustive stretch-shortening cycle exercise on muscle blood flow during exercise

Aim:  The influence of exhaustive stretch‐shortening cycle exercise (SSC) on skeletal muscle blood flow (BF) during exercise is currently unknown.

Skiing economy and efficiency in recreational and elite cross-country skiers

Abstract Ainegren, M, Carlsson, P, Tinnsten, M, and Laaksonen, MS. Skiing economy and efficiency in recreational and elite cross-country skiers. J Strength Cond Res 27(5): 1239–1252, 2013—The purpose of this study was to investigate and compare skiing economy and gross efficiency in cross-country skiers of different performance levels, ages and genders; male recreational skiers and elite senior and junior cross-country skiers of both genders. The skiers performed tests involving roller skiing on a treadmill using the gear 3 and diagonal stride techniques. The elite cross-country skiers were found to have better skiing economy and higher gross efficiency (5–18%) compared with the recreational skiers (p < 0.05) and the senior elite had better economy and higher efficiency (4–5%) than their junior counterparts (p < 0.05), whereas no differences could be found between the genders. Also, large ranges in economy and gross efficiency were found in all groups. It was concluded that, in addition to V[Combining Dot Above]O2peak, skiing economy and gross efficiency have a great influence on the differences in performance times between recreational and junior and senior elite cross-country skiers, as well as between individual skiers within the different categories. Thus, we recommend cross-country skiers at all performance levels to test not only V[Combining Dot Above]O2peak, but also skiing economy and efficiency.

DETERMINANTS OF A SIMULATED CROSS-COUNTRY SKIING SPRINT COMPETITION USING V2 SKATING TECHNIQUE ON ROLLER SKIS

Mikkola, J, Laaksonen, M, Holmberg, H-C, Vesterinen, V, and Nummela, A. Determinants of a simulated cross-country skiing sprint competition using V2 skating technique on roller skis. J Strength Cond Res 24(4): 920-928, 2010-The present study investigated the performance-predicting factors of a simulated cross-country (XC) skiing sprint competition on roller skis, on a slow surface. Sixteen elite male XC skiers performed a simulated sprint competition (4 × 850 m heat with a 20-minute recovery) using V2 skating technique on an indoor tartan track. Heat velocities, oxygen consumption, and peak lactate were measured during or after the heats. Maximal skiing velocity was measured by performing a 30-m speed test. Explosive and maximal force production in the upper body was determined by bench press (BP). Subjects also performed maximal anaerobic skiing test (MAST) and the 2 × 2-km double poling (DP) test. The maximal velocity of MAST (VMAST) and velocities at 3 (V3), 5 (V5), 7 (V7) mmol·L−1 lactate levels in MAST were determined. In the 2 × 2-km test, DP economy (&OV0312;O2SUBDP) and maximal 2-km DP velocity (VDP2KM) were determined. The best single performance-predicting factors for the sprint performance were VDP2KM (r = 0.73, p < 0.01), V7 (r = 0.70, p < 0.01), and &OV0312;O2SUBDP (r = −0.70, p < 0.01). Faster skiers in sprint simulation had a higher absolute &OV0312;O2 (L·min−1) (p < 0.05-0.01) during sprint heats, and higher anaerobic skiing power (VMAST, p < 0.05) and better anaerobic skiing economy (V3, V5, V7, p < 0.05-0.001) than slower skiers. Faster skiers were also stronger in BP, with regard to both absolute (p < 0.01) and relative (p < 0.05) values. In addition, anaerobic characteristics seem to be of importance at the beginning of the XC skiing sprint competition, whereas the aerobic characteristics become more important as the XC skiing sprint competition progressed. This study indicates that sprint skiers should emphasize sport-specific upper body training, and training skiing economy at high speeds.

Myocardial perfusion after marathon running

We investigated the effects of acute prolonged exercise (marathon running) on cardiac function and myocardial perfusion. Cardiac dimensions and function were measured in seven endurance‐trained men using echocardiography before and repeatedly after marathon (42.2 km) running (at 10 min, 150 min, and 20 h). Myocardial perfusion and perfusion resistance were measured using positron emission tomography and 15O‐H2O before and 85–115 min after running. Echocardiographic indices showed only mild and clinically non‐significant changes in cardiac function after running. Rate‐pressure‐corrected basal myocardial perfusion (0.89±0.13 vs. 1.20±0.32 mL min−1 g−1, P=0.04) was increased after running. Also, adenosine‐stimulated perfusion tended to be higher (3.67±0.81 vs. 4.47±0.52 mL min−1 g−1, P=0.12) and perfusion resistance during adenosine stimulation was significantly lower after running (26±6 vs. 18±3 mmHg min g mL−1, P=0.03). Plasma free fatty acid (FFA) concentration was significantly increased after running. These results show that marathon running does not cause marked changes in cardiac function in healthy men. Basal perfusion was increased after exercise, probably reflecting changes in fuel preferences to increased use of FFAs. Strenuous exercise also seems to enhance coronary reactivity, which could thereby serve as a protective mechanism to vascular events after exercise.

Motion detection and correction for dynamic 15O-water myocardial perfusion PET studies

PurposePatient motion during dynamic PET studies is a well-documented source of errors. The purpose of this study was to investigate the incidence of frame-to-frame motion in dynamic 15O-water myocardial perfusion PET studies, to test the efficacy of motion correction methods and to study whether implementation of motion correction would have an impact on the perfusion results.MethodsWe developed a motion detection procedure using external radioactive skin markers and frame-to-frame alignment. To evaluate motion, marker coordinates inside the field of view were determined in each frame for each study. The highest number of frames with identical spatial coordinates during the study were defined as “non-moved”. Movement was considered present if even one marker changed position, by one pixel/frame compared with reference, in one axis, and such frames were defined as “moved”. We tested manual, in-house-developed motion correction software and an automatic motion correction using a rigid body point model implemented in MIPAV (Medical Image Processing, Analysis and Visualisation) software. After motion correction, remaining motion was re-analysed. Myocardial blood flow (MBF) values were calculated for both non-corrected and motion-corrected datasets.ResultsAt rest, patient motion was found in 18% of the frames, but during pharmacological stress the fraction increased to 45% and during physical exercise it rose to 80%. Both motion correction algorithms significantly decreased (p<0.006) the number of moved frames and the amplitude of motion (p<0.04). Motion correction significantly increased MBF results during bicycle exercise (p<0.02). At rest or during adenosine infusion, the motion correction had no significant effects on MBF values.ConclusionSignificant motion is a common phenomenon in dynamic cardiac studies during adenosine infusion but especially during exercise. Applying motion correction for the data acquired during exercise clearly changed the MBF results, indicating that motion correction is required for these studies.

Changes in performance and poling kinetics during cross-country sprint skiing competition using the double-poling technique

In this study, changes in skiing performance and poling kinetics during a simulated cross-country sprint skiing competition were investigated. Twelve elite male cross-country skiers performed simulated sprint competition (4 × 1,150 m heat with 20 min recovery between the heats) using the double-poling technique. Vertical and horizontal pole forces and cycle characteristics were measured using a force plate system (20-m long) during the starting spurt, racing speed, and finishing spurt of each heat. Moreover, heat and 20-m phase velocities were determined. Vertical and horizontal pole impulses as well as mean cycle length were calculated. The velocities of heats decreased by 2.7 ± 1.7% (p = 0.003) over the simulated competition. The 20-m spurting velocity decreased by 16 ± 5% (p < 0.002) and poling time increased by 18 ± 9% (p < 0.003) in spurt phases within heats. Vertical and horizontal poling impulses did not change significantly during the simulation; however, the mean forces decreased (p < 0.039) (vertical by 24 ± 11% and horizontal by 20 ± 10%) within heats but not between the heats. Decreased heat velocities over the simulated sprint and spurting velocities within heats indicated fatigue among the skiers. Fatigue was also manifested by decreased pole force production and increased poling time.

Evidence of Improved Shooting Precision in Biathlon After 10 Weeks of Combined Relaxation and Specific Shooting Training

The aim of this study was to test the hypothesis that a combined relaxation (applied tension release, ATR) and specific shooting training regimen may enhance shooting ability of biathlon athletes. Seven biathletes of high national level were randomized into an experimental group (age 20 ± 5 years; Vo 2max 60 ± 8 mL kg− 1 min− 1) and were asked to add this special training intervention to their regular training for 10 weeks, while five other biathletes served as controls (age 19 ± 2 years; Vo 2max 57 ± 10 mL kg− 1 min− 1). The shooting ability of the subjects was assessed before and after the intervention at rest and after roller skiing on a treadmill in a laboratory-based competition simulating assessment. After the intervention period, the experimental group demonstrated a significantly enhanced shooting performance compared to the control group. No changes in Vo 2max or in heart rate and Vo 2 responses were observed before and after the intervention in either group and there were no differences between the groups in these parameters. Thus, the preliminary conclusion is that a combination of ATR and specific shooting training seems to be instrumental in enhancing the shooting performance in biathlon.

V˙O2peak, Myocardial Hypertrophy, and Myocardial Blood Flow in Endurance-Trained Men

INTRODUCTION Endurance training induces cardiovascular and metabolic adaptations, leading to enhanced endurance capacity and exercise performance. Previous human studies have shown contradictory results in functional myocardial vascular adaptations to exercise training, and we hypothesized that this may be related to different degrees of hypertrophy in the trained heart. METHODS We studied the interrelationships between peak aerobic power (V˙O2peak), myocardial blood flow (MBF) at rest and during adenosine-induced vasodilation, and parameters of myocardial hypertrophy in endurance-trained (ET, n = 31) and untrained (n = 17) subjects. MBF and myocardial hypertrophy were studied using positron emission tomography and echocardiography, respectively. RESULTS Both V˙O2peak (P < 0.001) and left ventricular (LV) mass index (P < 0.001) were higher in the ET group. Basal MBF was similar between the groups. MBF during adenosine was significantly lower in the ET group (2.88 ± 1.01 vs 3.64 ± 1.11 mL·g·min, P < 0.05) but not when the difference in LV mass was taken into account. V˙O2peak correlated negatively with adenosine-stimulated MBF, but when LV mass was taken into account as a partial correlate, this correlation disappeared. CONCLUSIONS The present results show that increased LV mass in ET subjects explains the reduced hyperemic myocardial perfusion in this subject population and suggests that excessive LV hypertrophy has negative effect on cardiac blood flow capacity.

The association between muscle EMG and perfusion in knee extensor muscles.

The relationships between electromyographic (EMG) activity and force as well as muscle blood flow and work have been well established. However, the association between muscle blood flow and EMG activity remains unsolved. Thus, to test the hypothesis that muscle EMG activity relates to muscle perfusion in different compartments of the quadriceps femoris (QF) muscle, 12 healthy male subjects were studied. During two very submaximal exercise bouts, at different exercise intensities, oxygen labelled radiowater and positron emission tomography were used to measure muscle perfusion. In addition, produced force of knee extensors and muscle EMG activity in the vastus lateralis (VL), vastus medialis (VM) and rectus femoris (RF) muscles were recorded during both exercise bouts. Although the exercise intensity and average force production was higher during the second exercise bout (38 ± 15 versus 51 ± 17 N; P = 0·007), the mean EMG activity was lower (RF; P<0·001) or unchanged (VL; P = 0·722 and VM; P = 0·640). During the second exercise period, perfusion also remained unchanged in the entire QF muscle (P = 0·223) and in its separate muscles (VL, P = 0·703; VM, P = 0·141; RF, P = 0·113) in a group level. However, the individual changes in muscle perfusion were tightly related to changes in muscle EMG activity in VL (r = 0·84; P = 0·002) and VM (r = 0·68; P = 0·015) but poorly in the RF muscle (r = 0·40; P = 0·257). In conclusion, the different associations between muscle perfusion and EMG activity in different QF muscles suggests specific functional role of the vasti muscles and the RF muscle.