Cankar G. et al.
EQOL (2009) 33-37
VERTICAL JUMP PERFORMANCE AND POWER DROP
AFTER 35 DAYS OF BED REST
Gregor Cankar*, Boštjan Šimunič* , Jörn Rittweger**, and Rado Pišot*
* Institute of Kinesiology Research, Science and Research Centre of Koper, University of Primorska,
Koper, Slovenia
** Institute for Biomedical Research into Human Movement and Health, Manchester Metropolitan
University, UK
Abstract
Physical - sport inactivity is often associated with loss of muscle mass, positive energy balance, fat gain,
injuries, motor incompetence, and many others negative effects. The goal of this study was to evaluate
loss of muscle function and performance as a response to total physical inactivity. Ten healthy male
volunteers (age: 23.3 ± 2.2 years; body height: 179 ± 7.1 cm; body mass: 75.2 ± 9.3 kg) were measured
before and after 35 days of horizontal bed rest. Energy intake was adapted from the beginning of the bed
rest and associated with weekly changes in body mass and fat mass. Peak muscle power and maximal
jump height was measured during vertical jump test, performed before and after bed rest. Maximum
jumping power and jumping height decreased significantly after bed rest, for 10 W·kg-1 (19.2 %;
P<0.001) and 11.2 (22 %; P<0.001), respectively. Inter subjects’ variability of the jumping height results
was in the range from 8.6 % to 49.1 % and for jumping height from 6.8 % to 31.3 %. Results of this study
confirm that vertical jump test demands vigorous human performance and should be conducted after bed
rest studies in special care and considering huge inter subject variability in designing studies.
Keywords: bed rest, skeletal muscle, vertical jump, jump power, jump height
Introduction
Nowadays many athletes have problems with injuries which consequently lead to loss of training days,
muscle mass, muscle strength, and consequently to loss of performance. Lack of sport exercise leading
into unbalanced (positive) energy intake reflects mainly in fat deposits. Sport exercise physiology is well
investigated area in science and sport. To understand positive effects of sport activity we have to
understand also effects after periods of inactivity. There are many different approaches to study how
physical inactivity reflects on human organism. Some scientists have been studying effects of long
duration space flights (Pavy-Le Traon et al.,1998; Le Blanc et al., 2000a; Blottner et al., 2006), other
studies were done with simulation of weightlessness (Adams et al., 2003; Mekjavić et al., 2005; Rittweger
et al., 2006; Rittweger et al., 2007; Pišot et al., 2008), or immobilization of healthy (Rittweger et al.,
2006; Ferrando et al., 1996) or injured (Hyeteok et al., 2003; Pathare et al., 2005) body parts.
Recent findings have shown that effects of bed rest on human organism are similar as effects
sedentary lifestyle and ageing, but different mechanisms involved. Effects can be seen in all human
systems: loss of bone mass (Lang et al., 2004; Le Blanc et al., 2000a and 2000b), loss of muscle mass
(Adams et al., 2003; Kawakami et al., 2001), changes in body composition (Kawakami et al., 2001; Kubo
et al., 2004; Šimunič et al., 2008), loss of muscle function (Pathare et al., 2005; Duchateau et al., 1987;
Alkner & Tesch, 2004; Lang et al., 2004) and impairment of cardiac circulatory system (Mekjavić et al.,
2005).
Jumping power and jumping height is used as a performance test in many sports. Therefore,
scientists use the test to evaluate short- and long- term adaptations on various training/detraining
impulses. The data from different studies and within the same studies show great discrepancies. So far we
know that muscle power declines with exposure to bed rest from 9 to 16 % per month (Rittweger et al.,
33
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EQOL (2009) 33-37
2007; Ferretti et al., 2001), while jump height 10.7 % per month (Rittweger et al., 2007). Furthermore,
Rittwegger et al. (2007) reports inter subjects’ variations in loss of jump power and loss of jump height
from 9 to 31 % and from 14 to 48 %, respectively. Additionally, scientists evaluate jump performance
typically after 2 to 4 days after reambulation. Rittwegger et al. (2007) was the first to demonstrate jump
power measurements immediately after reambulation. He reported particularly strong muscle soreness
during the first days of recovery and therefore only 70% of jumps performed and some of them performed
sub-maximal.
Maximal jump test is very vigorous performance test containing elements of explosiveness with
maximal force production in short time and is widely used in sports. Therefore, our concern was in test
results obtained immediately after bed rest deconditioning and reporting inter subjects’ variability.
Methods
PARTICIPANTS: Ten healthy males without history of cardiovascular and musculoskeletal illnesses
were selected for study of 35 days of 6° head down tilt bed rest. Bed rest study was performed in
Orthopaedic Hospital Valdoltra. The experimental protocol was approved by the Ethical Committee of
the University of Ljubljana, Slovenia and conformed to the standards set by the Declaration of Helsinki
(2002). All volunteers were previously informed about procedures and risk factor involved and submitted
written informed consent.
VERTICAL JUMP TEST: Jump test was performed before bed rest (BDC) and immediately
after reambulation (POST). Vertical countermovement jumps, with athletic shoes and with the hands
posed on the hips, were performed on a ‘Leonardo’ ground reaction platform
(Novotec Medical,
Pforzheim, Germany). Every participant performed three maximal jumps from which highest jump and
corresponding power was selected for the further analyses. Data were sampled at 2000 Hz and stored on a
PC. The instruction to jump was to elevate the head as high as possible.
OTHER MEASUREMENTS: Body height and weight were measured with standard tools.
Muscle mass and fat mass were measured with bioimpedance method (Maltron BioScan 916S, UK).
STATISTICS: Personal data are presented as mean ± standard deviation, while variables’ data as
mean ± standard error. Results were analyzed with a repeated measures analysis of variance (ANOVA).
All comparisons were considered statistically significant at the conventional
0.05 level. Statistical
analysis was performed using SPSS statistical software (version 15; SPSS, Inc., Chicago, IL).
Results
All data are summarized in table 1. Participants have lost 3 kg (4 %; P<0.001) of body weight after 35
days of bed rest. Muscle mass after bed rest dropped for 1.1 kg (-3.4 %; P<0.001), while fat mass did not
decrease significantly (P=0.598).
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EQOL (2009) 33-37
Table 1: Average data collection before and immediately after bed rest
BDC
POST
P
Height / cm
179.0 ± 7.1
-
-
Body Weight / kg
75.2 ± 9.3
72.2 ± 8.7
0.000
Muscle mass / kg
32.0 ± 3.3
30.9 ± 3.2
0.000
Fat mass / %
15.8 ±3.6
15.7 ± 3.2
0.598
Jumping Power / W·kg-1
52.0 ± 2.7
42.0 ± 1.3
0.001
Jumping Height / cm
50.8 ± 2.4
39.6 ± 2.3
0.000
BDC: Baseline Data Collection; POST: After bed rest data collection; P statistical significance
Maximum jumping power and jumping height (Figures 1, 2) decreased significantly after bed
rest. We noted reduction of relative jumping power for 10 W·kg-1 (19.2 %; P<0.001) and similar
reduction of jump height of 11.2 (22 %; P<0.001).
Inter subjects’ variability for jumping height and jumping power was from 8.6 % to 49.1 % and
from 6.8 % to 31.3 %, respectively.
Discussion
In this study we evaluated performance drop in vertical jump after 35 days of physical inactivity. As far
as we know there was very little known about human performance deterioration in early minutes after bed
rest reambulation. On the other hand scientists also reports huge inter subject variability in the drop at
maximal performance tests after bed rest studies. Therefore our aim was to establish immediate leg power
and jumping height deterioration after 35 days of bed rest.
Our test was done within 30 min after reambulation, literally first 10 to 20 steps were made on
ground reaction platform. We found decrease of peak jump relative power and jump height after 35 days
of bed rest for 19.2 % and 22 %, respectively. Our findings are not in line with earlier reports made by
Rittweger et al. (2007), where they found reduction of jump peak power and height, after 90 days of bed
rest, by 25.8 % and 29.5 %, respectively. But are in line with Ferretti et al. (2001) where he found after 42
days of bed rest 22.7 % loss of maximal muscle power. He concluded that drop in calf plantar flexors
cross sectional area can be explained as reduction of muscle power output, if appropriately normalized.
70
Figure
1: Maximum jump
60
height before and after bed
rest.
50
40
30
20
10
0
BDC
POST
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EQOL (2009) 33-37
Figure 2: Maximum relative
75
jump power before and after
70
bed rest.
65
60
55
50
45
40
35
30
BDC
POST
BDC: Baseline Data Collection; POST: After bed rest data collection;
Furthermore, inter subjects’ variability was in line with findings of others. The lower and upper
limit for jumping height and jumping relative leg power was from 8.6 % to 49.1 % and from 6.8 % to
31.3 %, respectively. Rittweger et al. (2007) reported similar variability in jumping power from 8 % to 31
%, while in jumping height from 13 % to 48 %. In our study one subject sprain his ankle but performed
the jump test without pain. He reported the pain next day. Other subject next day complained about the
pain in the instep area. After physician examination he could continue the other tests during following
days. Both incidents confirmed that jump test demands vigorous human performance. Test as such is
standard evaluation test not just in sport but also in space studies and therefore should be considered with
special care. Large inter subjects’ variability should be considered carefully before applying such test in
future studies.
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