Mechanical load has been estimated during step exercise based on ground reaction force (GRF) obtained by force platforms. It is not yet accurately known whether these measures reflect foot contact forces once the latter depend on footwear and are potentially modified by the compliant properties of the step bench. The aim of the study was to compare maximal and mean plantar pressure (PP), and maximal GRF obtained by pressure insoles after performing seven movements both over two metal force platforms and over the step bench. Fifteen step-experienced females performed the movements at the cadences of 130 and 140 beats per minute. PP and GRF (estimated from PP) obtained for each floor condition were compared. Maximal PP ranged from 29.27 ± 9.94 to 47.07 ± 12.88 N/cm2 as for metal platforms, and from 28.20 ± 9.32 to 43.00 ± 13.80 N/cm2 as for the step bench. Mean PP ranged from 11.09 ± 1.62 to 14.32 ± 2.06 N/cm2 (platforms) and from 10.71 ± 1.54 to 14.22 ± 1.77 N/cm2 (step bench). GRF (normalized body weight) ranged from 1.43 ± 0.14 to 2.41 ± 0.24 BW (platforms) and from 1.38 ± 0.14 to 2.36 ± 0.19 BW (step bench). No significant statistical differences were obtained for most of the comparisons between the two conditions tested. The results suggest that metal force platform surfaces are suitable to assess mechanical load during this physical activity. The forces applied to the foot are similar to the softer step bench and the hard force platform surface. This may reflect the ability of the performers to adapt their movement patterns to normalize the impact forces in different floor conditions.
Rita Santos-Rocha and António Veloso
Deanna L. Huggett, Ian D. Elliott, Tom J. Overend and Anthony A. Vandervoort.
The authors compared heart-rate and blood-pressure responses to typical isometric (ISO) and isokinetic (90°/s) eccentric (ECC) resistance-training protocols in older adults. Twenty healthy older adults (74 ± 5 years old) performed randomly ordered ISO and isokinetic ECC exercise (3 sets of 10 repetitions) at a target intensity of 100% of their peak ISO torque value. Heart rate and systolic (SBP) and diastolic (DBP) blood pressures were recorded continuously, and mean arterial pressure (MAP) and rate-pressure product (RPP) were calculated. ECC peak torque (139 ± 33 N · m) was significantly greater than ISO peak torque (115 ± 26 N · m; p < .001). All variables increased significantly (p < .001) during both ISO and ECC exercise. Changes in SBP, DBP, MAP, and RPP were significantly greater during ISO exercise than during ECC exercise (p < .001). Clinically, an isokinetic ECC exercise program enables older adults to work at the same torque output with less cardiovascular stress than ISO exercise.
Hélène Perrault, Maria Tzovanis, Dominique Johnson, André Davignon, Claude Chartrand, Abdelkader Mokrane and Réginald A. Nadeau
This study compares the autonomic responses of 9 adolescents (mean ± SEM: 17±1 years) successfully operated for tetralogy of Fallot (TOF) in early childhood and 8 age-matched healthy controls (CTRL) using R-R and blood pressure variability. Continuous ECG and BP recordings were obtained during spontaneous and controlled respiration (CR) at 0.20 Hz as well as after an 85° head-up tilt (HUT) and during steady-state cycling at heart rates of 100 and 120 bpm, selected to reflect partial and complete cardiac vagal withdrawal. TOF exhibited total R-R variance and HF power (ms2) lower than CTRL under both spontaneous (938 ± 322 vs. 1,714 ± 296) and CR (1,541 ± 527 vs. 4,725 ± 1,207; p < .05), which may be indicative of a lower cardiac vagal activity. HUT decreased the R-R HF component, which remained lower in TOF than CTRL and increased the diastolic BP LF component in TOF but not in CTRL. Exercise decreased the R-R HF power more in TOF than CTRL. The exaggerated diastolic BP and limited heart rate responses to tilting and the more marked vagal withdrawal at Ex120 in TOF may be suggestive of a disturbance in the cardiac sympathetic response. Further studies are needed to confirm these observations on larger groups of young adults successfully operated for TOF.
Joaquin U. Gonzales, Dustin M. Grinnell, Martha J. Kalasky and David N. Proctor
The authors examined interindividual and sex-specific variation in systolic (SBP) and diastolic (DBP) blood pressure responses to graded leg-extension exercise in healthy older (60–78 yr) women (n = 21) and men (n = 19). Maximal oxygen uptake (VO2max), body composition, physical activity (accelerometry), and vascular function were measured to identify predictors of exercise BP. Neither VO2max nor activity counts were associated with the rise in SBP or DBP during exercise in men. The strongest predictors of these responses in men were age (SBP: r 2 = .19, p = .05) and peak exercise leg vasodilation (DBP: r 2 = –.21, p < .05). In women, the modest relationship observed between VO2max and exercise BP was abolished after adjusting for central adiposity and activity counts (best predictors, cumulative r 2 = .53, p < .05, for both SBP and DBP). These results suggest that determinants of variation in submaximal exercise BP responses among older adults are sex specific, with daily physical activity influencing these responses in women but not men.
Jonathan Sinclair, Sarah J. Hobbs, Paul J. Taylor, Graham Currigan and Andrew Greenhalgh
In running analyses where both kinetic and kinematic information is recorded, participants are required to make foot contact with a force and/or pressure measuring transducer. Problems arise if participants modify their gait patterns to ensure contact with the device. There is currently a paucity of research investigating the influence of different underfoot kinetic measuring devices on 3-dimensional kinematics of running. Fifteen participants ran at 4.0 m/s in four different conditions: over a floor embedded force plate, Footscan, Matscan, and with no device. Three-dimensional angular kinematic parameters were collected using an eight camera motion analysis system. Hip, knee, and ankle joint kinematics were contrasted using repeated-measures ANOVAs. Participants also rated their subjective comfort in striking each of the three force measuring devices. Significant differences from the uninhibited condition were observed using the Footscan and Matscan in all three planes of rotation, whereas participants subjectively rated the force plate significantly more comfortable than either the Footscan/Matscan devices. The findings of the current investigation therefore suggest that the disguised floor embedded force plate offers the most natural running condition. It is recommended that analyses using devices such as the Footscan/Matscan mats overlying the laboratory surface during running should be interpreted with caution.
Jane E. Yardley, Jacqueline Hay, Freya MacMillan, Kristy Wittmeier, Brandy Wicklow, Andrea MacIntosh and Jonathan McGavock
Type 2 diabetes is associated with hypertension and an increased risk of cardiovascular disease. In adults, blood pressure (BP) responses to exercise are predictive of these complications. To determine if the hemodynamic response to exercise is exaggerated in youth with dysglycemia (DG) compared with normoglycemic overweight/obese (OB) and healthy weight (HW) controls a cross-sectional comparison of BP and heart rate (HR) responses to graded exercise to exhaustion in participants was performed. DG and OB youth were matched for age, BMI z-score, height and sex. Systolic (SBP) and diastolic BP (DBP) were measured every 2 min, and HR was measured every 1 min. SBP was higher in OB and DG compared with HW youth at rest (p > .001). Despite working at lower relative workloads compared with HW, the BP response was elevated during exercise in OB and DG. For similar HR and oxygen consumption rates, BP responses to exercise were slightly higher in OB and DG compared with HW. OB and DG youth both display elevated resting and exercise BP relative to HW peers. Obesity may play a greater role than dysglycemia in the exaggerated BP response to exercise in youth.
Borut Fonda and Nejc Sarabon
It has been reported in practice that the application of lower-body negative pressure (LBNP) to elite athletes during periods of intense training can help aid recovery.
To examine the effects of LBNP on biochemical, pain, and performance parameters during a 5-d recovery period after a damaging plyometric-exercise bout.
Randomized controlled study.
24 healthy young female adults were randomly allocated into 2 groups. Before and 1, 24, 48, and 96 h after the damaging exercise for hamstrings (50 drop jumps and 50 leg curls), participants underwent a series of tests (blood samples, pain sensation, countermovement jump, maximal isometric torque production, maximal explosive isometric torque production, and 10-m sprint). After the damaging exercise, the experimental group was exposed to intermittent LBNP therapy daily for 60 min.
There was a statistically significant interaction (P < .05) between the experimental and control groups for maximal strength, explosive strength, pain sensation, and vertical jumps (maximal power and force). No statistically significant interaction was present for the biochemical markers, jump height, and 100-m sprint.
LBNP therapy could improve recovery by limiting the loss in muscle strength and power and limiting the presence of pain.
Cyril Burdet and Patrice Rougier
To question the relation between uni- and bipedal postural skills, 21 subjects were required to stand on a force platform through uni- and bipedal conditions. These two protocols are commonly used paradigms to assess the balance capacities of healthy and disabled patients. The recorded displacements of the center of pressure (CP) were decomposed along mediolateral and anteroposterior axes and assessed through variance positions and parameters obtained from fractional Brownian motion (fBm) modeling to determine the nature and the spatiotemporal organization of the successive controlling mechanisms. The variances underline the relative independence of the two tasks. Nevertheless, as highlighted by the fBm framework, postural correction is initiated for the unipedal stance after shorter time delays and longer covered distances. When compared to bipedal standing, one of the main characteristics of unipedal standing is to induce better-controlled CP trajectories, as deduced from the scaling regimes computed from the fBm modeling. Lastly, the control of the CP trajectories during the shortest time intervals along the anteroposterior axis appears identical for both uni- and bipedal conditions. Unipedal and bipedal standing controls should thus be viewed as two complementary tasks, each providing specific and complementary insights into the postural control organization.
Brad Hodgson, Laurie Tis, Steven Cobb, Shawn McCarthy and Elizabeth Higbie
Because of research variability and the increasing use of orthotics to manage lower extremity problems, further research is warranted.
To investigate the effect of rear-foot- and forefoot-posted (PAL) and mediolongitu-dinal arch-supported (SOLE) orthotics on plantar pressure (PP) during walking.
17 subjects with forefoot varus.
Data were collected at 0 and 6 weeks for no-orthotic and orthotic conditions.
PPs were collected with the EMED Pedar measurement system.
Zero weeks: PAL increased PP in lateral forefoot (LFF), middle toes (MT), and lateral toes (LT) and decreased PP in lateral heel (LH), medial forefoot (MFF), and central forefoot (CFF). SOLE increased PP for midfoot (MF) and LT and decreased PP in medial heel (MH), LH, and CFF. 6 weeks: PAL increased PP in LFF, MT, and LT and decreased PP in LH, MFF, and CFF. SOLE increased PP in MF and decreased PP in MH, LH, and LFF.
The SOLE orthotic appeared to be more effective in attaining the goals of custom-molded-orthotic intervention.
W. Jack Rejeski, Karen M. Neal, Martine E. Wurst, Peter H. Brubaker and Walter H. Ettinger Jr.
An elderly patient population was used to investigate whether an acute bout of aerobic exercise (AE) would reduce systolic blood pressure (SBP) to a greater extent than would a bout of weight lifting (WL). SBPs were studied in the context of a laboratory Stressor as well as during activities of daily living using ambulatory monitoring devices (AMBPs). Patients participated in a laboratory Stressor and were monitored via AMBP for 8 hr. SBPs were lower for up to 5 hr postexercise for the AE treatment only. In addition, in comparison to no-exercise control data, baseline SBP was lower for the AE group than the WL group prior to the Stressor. Subjects in the AE condition also tended to have lower SBP responses following exercise than patients in the WL group, although these differences did not reach a conventional level of statistical significance. These data provide evidence that single bouts of AE, but not WL, may lower SBP in elderly patients, even for those who have compromised function due to osteoarthritis of the knee.