Hydrodensitometry (HD), skinfold thickness measurements (SK), and dual-energy X-ray absorptiometry (DXA) were compared for estimating percent body fat (%BF) in youth competitive swimmers. Agreement was assessed using Bland-Altman plots and linear regression of the differences between methods compared to method means. Limits of agreement between the three techniques were large. Hydrodensitometry and SK demonstrated no difference in precision. Variance was observed between DXA and the other two techniques, with DXA demonstrating a wider distribution of measurement scores than HD or SK. These methods do not appear to be interchangeable when measuring percent body fat in youth swimmers.
Georgianna Tuuri and Mark Loftin
Scott Owens, Laurel Lambert, Suzanne McDonough, Kenneth Green and Mark Loftin
This pilot study examined the feasibility of an interactive obesity prevention program delivered to a class of fourth-grade students utilizing daily e-mail messages sent to the students’ home computers. The study involved a single intact class of 22 students, 17 (77%) of whom submitted parental permission documentation and received e-mail messages each school day over the course of one month. Concerns regarding Internet safety and children’s use of e-mail were addressed fairly easily. Cost/benefit issues for the school did not seem prohibitive. Providing e-mail access to students without a home computer was accomplished by loaning them personal digital assistant (PDA) devices. In larger interventions, loaning PDAs is probably not feasible economically, although cell phones may be an acceptable alternative. It was concluded that this type of interactive obesity prevention program is feasible from most perspectives. Data from a larger scale effectiveness study is still needed.
Marc Bonis, Mark Loftin, Richard Speaker and Anthony Kontos
The purpose of the study was to investigate the seasonal relationship of athletic amenorrhea and body composition in elite, adolescent, cross-country runners. The participants consisted of 28 female adolescent cross-country runners (mean age ± SD = 15.4 ± 1.5 years); 17 eumenorrheics and 11 amenorrheics. The participants’ body composition was measured pre- and postseason using dual-energy X-ray Absorptiometer (DXA). The eumenorrheics’ postseason BMD was significantly greater than the amenorrheics’ postseason BMD (F(1,54) = 16.22, p < .05, partial η 2 = .231). The eumenorrheics’ postseason bodyweight (F(1,54) = 7.65, p < .05, partial η 2 = .124), BF (F(1,54) = 8.56, p < .05, partial η 2 = .137), and BMC (F(1,54) = 8.52, p < .05, partial η 2 = .136) were significantly greater than the amenorrheic subgroup. There was also a significant seasonal increase in BMD (t(27) = –4.01, p < .05) for the overall group and the eumenorrheic subgroup (t(16) = –3.90, p < .05). Bodyweight best predicted BMD (F(1,26) = 46.434, p < .05, R2 = .641). In the study, athletic amenorrhea was highly associated with lower levels of BMD in the participants, and crosscountry running was highly associated with increased BMD.
Takashi Abe, Jeremy P. Loenneke, Robert S. Thiebaud and Mark Loftin
Context: Studies developed the frail elderly handgrip strength (HGS) diagnostic criteria using multiple types of handgrip dynamometers. If different handgrip dynamometers report different values, then this would have the potential to misclassify people into the wrong diagnostic category. Objective: To examine the characteristics of HGS measured by 2 standard handgrip dynamometers and to investigate the influence of hand size on HGS. Setting: University research laboratory. Participants: A total of 87 young and middle-aged adults between the ages of 20 and 60 years participated in this study. Main Outcome Measures: Standard methods of HGS measurements were used for hydraulic and Smedley spring-type dynamometers, although the participants were instructed to maintain an upright standing position in both tests. Results: Test–retest reliability of hydraulic and Smedley dynamometers provided comparable results to that observed with previous studies. However, the difference in HGS between the 2 dynamometers (Hydraulic–Smedley difference) was positively associated (r = .670, P < .001) with the mean of the 2 dynamometers. The participants who had relatively low HGS (at least <35 kg) produced similar HGS values when the 2 dynamometers were compared, whereas persons who had relatively higher HGS (at least >45 kg) produced greater strength values with the hydraulic compared with the Smedley. The hand and palm lengths were weakly correlated (r = .349 and r = .358, respectively, both Ps < .001) with the difference in HGS between the 2 dynamometers. Conclusions: Test–retest reliability of hydraulic and Smedley dynamometers provides comparable results to previous studies. However, the difference in HGS between the 2 dynamometers was positively associated with the mean of the 2 dynamometers. This Hydraulic–Smedley difference would not affect persons who have relatively low HGS (at least <35 kg), while when HGS is relatively high, the comparison between dynamometers should be done with caution.
Mark Loftin, Patricia Strikmiller, Barbara Warren, Leann Myers, Leslie Schroth, James Pittman, David Harsha and Melinda Sothern
Peak cardiorespiratory responses, physical activity patterns, and the association of VO2peak and physical activity were examined in 16 elementary (ES) and 16 high school (HS) females. Peak responses were assessed during treadmill running, and physical activity patterns were examined over two 12-hour weekdays. Results indicated similar relative VO2peak responses between groups (ES: M = 46.8 ml · kg−1 · min−1;HS:M = 46.6 ml · kg−1 · min−1). No statistical differences (p ≤ .05) were noted when moderate to vigorous physical activity (MVPA) and vigorous physical activity (VPA) were compared. Also, a three-way (Group × HR level × Sustained minutes) ANOVA revealed no statistical differences. A median correlation (r = .27) was found from 8 independent correlations of habitual physical activity and VO2peak. ES and HS appeared similar in regard to VO2peak, accumulative and sustained MVPA and VPA. Low levels of sustained MVPA and VPA (≥ 10 min) were evident in both groups.
Mark Loftin, Melinda Sothern, Georgianna Tuuri, Connie Tompkins, Cathie Koss and Marc Bonis
The aim of this investigation was to compare gender differences in physiologic and perceptual responses during a 1-h run at recent marathon pace and running economy at three speeds in recreational marathon runners.
In a counterbalanced design, 10 men and 10 women completed a 1-h treadmill run and a running economy test. Treadmill speed for the 1-h run ranged from 141 to 241 m·min−1 and 134, 168, and 188 m·min−1 for running economy. Physiologic parameters (oxygen uptake, carbon dioxide production, pulmonary ventilation, and heart rate) and perceived exertion were measured. Repeated-measures ANOVA was used to compare any gender differences (P < .05) during the 1-h run and a two-way ANOVA was used to compare running economy. With this sample, estimated marathon energy expenditure, body composition, and maximal physiologic function was reported.1
With the exception of an allometric expression of VO2 (mL·min−1·kg BW−0.75), similar gender physiologic and perceptual responses were found during the 1-h run. Although not significant, the females exercised at a higher percent VO2max (8% to 9%) during the run. Similar gender differences were also noted during the running economy tests.
Although the male runners completed a recent marathon significantly faster than the females, similar gender physiologic and perceptual responses were generally found during the 1-h treadmill run and the running economy tests.