LOAD COMPARISON RATIO IN SINGLE AND DOUBLE LEG
When comparing or prescribing loads for single leg (SL) squat or
jump movements there is a tendency to assume that the load
will be half of what an athlete performs in the double leg (DL)
movement. Whilst this is a reasonable starting point, the reality
is that the SL movement is more challenging and we cannot
make this assumption.
The aims of this study were to develop a theoretical model to
determine the load ratio between SL and DL movements and to
compare against actual force data in SL and DL
Countermovement Jumps (CMJ’s).
The model was based on the segmental weight distributions
acting above or rotating about the hip joint(s) in SL and DL squat
or jump movements.
Segmental data of Dempster (1955) indicates that the combined
body weight (BW) acting above the hips in aDL movement is
68%, that acting about the hip in aSL movement is 84% (see
Figure 1. Segmental weight distribution acting above or about the
hip joints in DL and SL movements
We can therefore estimate SL forces on the basis of the
SLFORCE = 0.81 xDLFORCE (equation 1),
where (68/84 = 0.81).
To test this model five male athletes (age 16 ±1 year, body mass
65.6 ±9.2kg) were tested performing DL and SL CMJ’s on a
Kistler force platform (type 9287B) at 1000 Hz. Peak Forces were
collected over three trials and the average taken for each
Philip Graham-Smith1, Alex Natera1, Mark Jarvis2
Aspire Academy for Sporting Excellence, Doha, Qatar1
English Institute of Sport, UK2
RESULTS & DISCUSSION
Peak forces in the DL and SL CMJ’s were 1739N ±241 and 1458N
±215 respectively corresponding to jump height performances
of 37.5cm ±2.2 and 22.1cm ±2.1.
The estimated SL force from equation 1 was 1408N ±196 with a
standard error between actual and predicted forces of 62N.
Assuming an equal load distribution between limbs in aDL
movement, the SL movement equates to 1.62 times the
intensity in one leg of the DL movement. This is supported by
actual force data which was found to elicit a ratio of 1.67,
highlighting that the segmental approach provides a very good
To estimate the actual additional load to elicit the same relative
loading in limbs (one limb in aDL movement to that of aSL
movement) then we can derive from the following equation:
0.84 BW +SLADD. LOAD (BW) = 0.5 (0.68 BW +DLADD. LOAD (BW))
SLADD. LOAD (BW) = [(DLADD. LOAD (BW) –BW)] / 2 …….(equation 2)
Findings indicate that additional loads of less than one BW in a
DL movement will not develop the same level of loading (in
each leg) compared to aSL movement with no load. An
additional load of one BW applied to aSL movement is the
equivalent to aDL movement with an additional load of 3BW
(1/3rd of the DL additional load), (see Figure 2).
Figure 2. Comparison of additional loads in DL and SL movements
The use of segmental analysis and the evaluation of loads acting
above and around the hip joint(s) in SL and DL movements have
helped to provide some logical understanding of exercise
progression, the relative intensities of each and the amount of
additional loading required to elicit the same levels of loading
Dempster, W.T. (1955). Space requirements of the seated
operator. WADC technical report, Wright-Patterson Air Force
Base, OH. pp. 55-159.
UKSCA's 11th Annual Conference –31st July –2nd August 2015 - Chesford Grange, Warwickshire.